Quaife Limited Slip Differential

[macfly]

Quaife in the UK make an alternative to the Open Diff that comes with the Z8, their part # QDF10N. The Z8 LSD was originally adapted from a 540 part but we are now one generation on from that original unit which needed special shimming and grinding of the diff housing to fit. If you have ordered an LSD I would recommend getting Jim at Metric Mechanic to build your unit. It is where several of us here have sent ours to be built.


Limited Slip Differential by Grease Monkey.

I am somewhat mystified by some of the choices BMW made when outfitting the Z8. For instance, while they equipped the M5 with a limited-slip differential, the Z8 has to make do with an open differential. Once again, it seems they believed Z8 owners were not going to push their cars hard enough to need the benefits of BMW's highest performance equipment. Unwilling to setle for this omission, I have conducted extensive research into an aftermarket (BMW does not make one) source for a proper differential for the Z8.

In my opinion, the best limited-slip being built today is the Quaife Automatic Torque Biasing differential. This unique unit will supply power to the wheel which has the most traction in a continuously variable ratio up to 95%! This means when you are accelerating out of a corner and your outside tire is heavily weighted, most of the power will be transferred to that tire, preventing the wheelspin you would experience with an open differential which sends most of the power to the inside tire which has the least traction. Under straight line acceleration, the Quaife will split the torque equally between the 2 wheels, again providing maximum traction, as opposed to an open differential which will send most of the power to the wheel which is spinning. Plus, during normal street driving, the Quaife acts like an open differential making it simple to negotiate tight parking spaces, etc. Truly the best of both worlds! Furthermore, because Quaife uses gears to distribute the power rather than plates and clutches found in other limited-slip designs, there is virtually no wear involved and as a result, Quaife warrants the differential for the life of the car.

Quaife limited-slips are used in all forms of motorsport, including Formula One and on many of the WRC cars (the toughest test). Ford's new Focus rally car built for the WRC uses a Quaife differential as does the Noble GT which has been rated as the best handling car in the world by many car magazines.

The other reason I wanted to change the differential in my Z8 was to change the final drive ratio to one which would provide more acceleration, albeit with a reduction in top speed potential. The standard ratio is 3.38:1 and I wanted around a 10% higher ratio. This is a big enough change to insure noticeable acceleration improvements without causing excessive revving at cruising speeds.

The next step was to find someone to build a Quaife limited-slip for the Z8. A ordered a Quaife differential unit from a 540i which was mated to a 3.64:1 final drive gear from a European 735i. With some grinding of the diff housing this was a suitable replacement for the Z8's open differential. The new ratio is app. 8% higher which means I've got 8% more torque to play with! Remember, torque is what accelerates your car, not horsepower. A stock Z8 will have the equivalent of 400 lb/ft of torque with this differential and the newfound ability to put all of it to good use. As far as top speed is concerned, where the stock Z8 has a theoretical (not realistic) top end of 198 mph with the speed limiter removed, the 3.64 ratio only drops top end to 184. And since most Z8s are speed restricted to 155 mph or so, the difference is of no consequence. At the same time, second gear provides 60 mph at 7000 rpm so your 0-60 sprints will be awesome! As far as highway cruising is concerned, 3000 rpm provides 80 mph in 6th. Frankly, the stock Z8 is geared for European autobahn driving and the new ratio is much better suited for the way most Americans drive their cars.

The only problem assciated with a gear ratio change is the potential for the cruise control to get confused by the new rpm/mph relationship. The cruise control on the 540i malfunctions when the ratio is changed whereas the M5's does not. Your speedometer is unaffected by the change so there are no accuracy issues associated with the swap and DSC remains fully functional.

A complete 3.64:1 Quaife differential for the Z8 costs $3250 plus shipping. There is an additional core charge of $1450 which you might get refunded when you send your old differential back to your supplier. If you would prefer to keep your 3.38:1 ratio but want the benefits of the Quaife limited-slip, the cost is $2850 plus shipping. If you want the 3.64 gears but don't want the Quaife, the cost is $1850 plus shipping. And if you want to keep your old differential for posterity, you can pay the $1450 core charge plus the cost of the new unit. The Quaife limited-slip is warranted for the lifetime of the car.

Due to an excess of snow where I live, I have not been able to drive my Z8 with its new differential yet. As soon as the roads dry out, I will post my impressions. In the mean time, I can tell you that another Z8 owner has recently installed one of Brett's Quaifes in his 550 HP supercharged Z8 and he was thrilled with the results. With the open differential, this poor guy could never put his foot to the floor without the DSC going bananas or one wheel spinning uncontrollably. Now he can plant it and the car just accelerates at warp speed! What fun!

P.S. If you end up with the 3.64 gears in your Z8, let me know and I will send you an updated rpm/mph chart to match your new ratio. Enjoy!

GM

----------------------------------

Q&A with GM on the new Diff

Q: GM, don't you think that without putting in a closer ratio gearbox, installing a 3.64 rear axle would make 1st and 2nd gears too much of a "stump puller"? I haven't done the math, but it seems like you'd run out of revs pretty fast in those gears.

A: 3.64 is not that much different than stock. Redline in first is 39 mph stock and 36 mph with the new gears. Redline in second is 65 mph stock and 60 mph with 3.64. No where near what I would term a "stump puller". Interestingly enough, the M5 uses the same transmission as the Z8 (including gear ratios) but has a 3.15 final drive ratio plus smaller diameter tires than the Z8, yet its mph/rpm relationship is virtually identicle to the stock Z8s in all gears. One of the things Dinan does when they modifiy the M5 is to change the final drive ratio to 3.45:1 (a 10% increase) which results in mph/rpm figures which are virtually identicle to the Z8 with a 3.64! None of the magazines which tested the S2 M5 ever felt the gearing was too short.

Another point to consider is that if you bump the rev limiter to 7300, which is what Dinan does, your redline shifts in first gear come at 38 mph vs. 39 stock and second gear shifts come at 63 mph vs. 65 stock, so there really isn't much difference in terms of speed when you shift. The difference is you will get there sooner, which I believe was your original point. However, an 8% change is not considered radical by any standards; in fact, 10% is generally considered the minimum for the change to be noticeable!

Yes your first to second shift will come sooner, as will all other shifts at redline, but the difference is minimal and not impractical. I think installing a short shift kit would more than compensate for the change in response time. What I think is more important to consider is how the Z8 will respond to your right foot in the more commonly used gears of 3rd, 4th and 5th. With the 3.64 ratio, acceleration in these gears will be noticeably improved, more so than in the lower gears where the stock car already accelerates very strongly. I find these are the gears I play in the most and I think this is where the real improvements will be appreciated.

Would I play with transmission ratios, particularly 1st and 2nd, if I had the option? Yes I would, but the compromises involved in using 3.64 gears are ones I can easily live with, especially given the benefits in the higher gears.


Q: Where is the speedometer pickup? Is the sender at the half shafts or is it coming off the abs system? I know some of the automatic transmission cars have the sensor in the transmission so when you change the final drive ratio things are just not right. Cruise control, Speedometer reading and shift points are all off. The Z8 has some bad compromises. The tires were a joke. I am running Michelin Pilot Sports, Big difference. The clutch delay valve was a must do modification and the sway bars were too small. I had no idea that the Z8 had no Limited-Slip differential. My M5 has one so I assumed the Z8 had one as well. Now I know why I never liked the rear end handling under hard acceleration.

A: Z8's speedo uses the ABS sensors, which are monitoring wheel rotation, so any change in the final drive ratio will have no impact on accuracy. On the other hand, if you change the overall tire diameter, your speedo will be off.

You're absolutely right about some of the other compromises BMW made when they spec'd the Z8. They wouldn't have been my choices, but I probably don't fit the owner/driver profile they were working with. That is why I feel the need to modify what I consider to be one of the finest automobiles ever produced. All car designs have compromises which are meant to make them marketable to a particular audience. Performance cars sacrifice some comfort and practicality in order to satisfy performance oriented buyers. Family vehicles sacrifice performance so they can be more practical. High volume cars must appeal to a broad spectrum of buyers. Low volume cars can be fine tuned towards a more specialized market. In the case of the Z8, anticipated production was low enough to allow the designers to create an automobile which would appeal to a limited group of enthusiasts, which is why the Z8 is so special and unique. However, compromises were still part of the process and it really isn't until you get down to cars like the McLaren F1 that you get to a low enough volume level where compromise becomes unnecessary. Given the fact that the Z8 was apparently aimed at a slightly less rambunctious crowd than the one I run with, I find it necessary to modify my Z8 to create the exact vehicle I would have designed had I been in charge. BMW might have had trouble selling as many of "my" Z8s as they did of the one they chose to build, but my modified Z8 fits me like a glove and provides me as much pleasure as if they had custom built it for me. I enjoy being involved with my cars on this level and feel no qualms about modifying an icon like the Z8. After all, it's my car, not theirs!


Q: How difficult is it to install one of those and what are the mechanical downsides (eg- can you cause damage to other components?

A: Installation requires removal of the exhaust system after the exhaust manifolds, removal of one of the heat shields on the underside of the car, dsiconnection of O2 sensors, and removal of the drive shaft. Then, the differential can be unbolted from the half-shafts and its mounts and lowered out of the car. Having a hoist and a helper makes the job much easier. Alternatively, any competent mechanic can do the swap for you.

Note: If you're careful, you can remove the differential without removing the drive shaft, which simplifies the process somewhat, but you must be careful not to damage the universal joints and/or rubber boots in the process. Be sure to repack the driveshaft universal joint with grease upon reassembly. Koala Motor Sport recommends using RedLine Shockproof Lightweight gear oil. Change it after 1200 miles. Then every 30,000 or so. No extended high speed driving during initial break-in. Acceleration is OK.

There are no mechanical downsides to using the Quaife. Many manufacturers offer optional final drive ratios without the need to beef-up the drivetrain. Frankly, unless you run extremely wide and sticky rear tires, your tires will spin well before you would break any drivetrain parts.


Q: I was planning to change my diff. to Evosport 3.64 with lock up which is $5750 plus refundable core charge of $1,800 with 50% deposit. It is also possible to have 3.92 with a special order. But if you prefer Quaife Automatic Torque Biasing differential I will consider this one as well and its cheaper. What do you think about 3.92? I only drive in the city so I am driving around 80 km/h. Thank you very much for the information about Quaife Automatic Torque Biasing differentials.

A: I am convinced the Quaife will outperform any other limited slip, regardless of cost. I think you would get tired of the 3.92 after a while since you would need to shift much more often. If you were only interested in autocross work, it might make sense, but for street use I think it is excessive. 3.64 is a nice compromise.


Q: Is this Qauife differential the complete unit, ie enclosed "pumpkin" or is it the differential and gear/pinion individually that need to installed inside our existing case?

A: It is the complete unit (gears, differential, housing) ready to bolt in.


Q: What are the changes in car speed one would see between the two final drive ratios?

A: 3.38 vs 3.64


ratio - 1st/2nd/3rd/4th/5th/6th

3.38 = 22, 37, 56, 77, 94, 113 @ 4000 rpm
3.64 = 21, 35, 52, 71, 87, 105 @ 4000 rpm

3.38 = 28, 47, 70, 96, 118, 142 @ 5000 rpm
3.64 = 26, 43, 65, 89, 109, 132 @ 5000 rpm

3.38 = 33, 56, 85, 115, 141, 170 @ 6000 rpm
3.64 = 31, 52, 79, 107, 131, 158 @ 6000 rpm

3.38 = 39, 65, 99, 134, 165, 198 @ 7000 rpm
3.64 = 36, 60, 92, 124, 153, 184 @ 7000 rpm
3.64 = 38, 63, 96, 130, 160, 192 @ 7300 rpm (Dinan chip)


Below are some images of the old style "Mk1" LSD that was adapted from the 540 unit, but rquired some grinding of the diff housing.

[macfly]

This is a great link to help understand the mechanics of different diff set ups.

[thegunguy]

is this handy page at how stuff works.com.

[macfly]

There seems to be some confusion as to how to tell if your Z8 or Alpina has a Limited Slip Differential or not.

To begin with, you cannot make a determination based on wheelspin during straight line acceleration. If the weight on each rear wheel is equal and each tire achieves equal traction, a car with an open differential will show virtually the same behaviour as one with a LSD. I have an extensive collection of road test articles on the Z8 and many of them show pictures of the cars with smoke billowing out from under both wheelwells during standing starts. I even have some which show 2 equal length, parallel, black tire marks left behind after an aggressive standing start. I am convinced these cars did not have LSD.

The difference betweeen a car with LSD and one with an open differential would only show up when the weight and traction were different for each rear wheel. The most common circumstance where this difference exists is during cornering. The outside tire is much more heavily weighted than the inside tire and if power is applied, an open differential will send most of that power to the unweighted inside wheel, causing it to spin due to a lack of traction. Many of you have experienced this phenomenon in your Z8s. A good LSD would do the opposite.

An easy way to determine if your car has a LSD is to raise one rear wheel off the ground and with the transmission in neutral, spin the raised wheel with your hand. If it spins freely, you most likely have an open differential. If you feel resistance, you probably have a LSD. Another test is to lift both rear wheels off the ground, put the transmission in gear, and turn one of the wheels by hand. If the one on the other side rotates in the opposite direction, you most likely have an open differential. If they rotate in the same direction, you most likely have a LSD.

I say "most likely" because there are all kinds of LSDs out there and each one has a different level of "lock" and uses a different method of locking the two wheels together. In some cases, you could overcome the lock connection and get open differential behaviour. However, in most cases, the above described technique will give you an accurate assessment.

special thanks to Grease Monkey for sending in this info.

[macfly]

Quaife's own oil recommedation. Also for those of you who may be looking at the photos of the original 540 unit that was fitted above, your group buy units won't look like that, they'll look like this one below.

[Z8doc]

I have had my spare rear diff rebuilt using the Quaife and 3.64 gears. The unit is now being installed in my Z8 today. The rear gear oil I have chosen is RedLine gear oil 75W90 fully synthetic.

The question I have is that when the car was new, there was a mandatory 1500 mile service for the rear differential. I believe the only thing that they did in that service was change the rear gear oil and replaced it with new BMW Lifetime lubricant gear oil.

Does it make sense that I should do the same thing again with this new rear diff/Quaife and gears?

[macfly]

just based on caution, as after say 1,000 miles the color and deposits in the oil will be a good indication of all being well.

[thegunguy]

Depending on your settings, see the original interview with GM below/above. He notes that Koala specifies changing gear oil at 1,200.

[Z8doc]

What a performance boost ! I expected 1st gear to be about the same and overall assessment is that it is except you are through it like the snap of your fingers quick. 2nd gear still is a very strong pull and noticably quicker too. 3rd gear.... this is where you notice ALOT of difference. The acceleration is phenomenal here! Much better acceleration overall and for day to day American driving -- a definite must in my opinion. For highway cruizin' ... 80 mph is still comfortable although it now cruizes at 3000 rpm instead of 2500 like before. I do not mind as the melody of the Eisenmann Exhaust (another must upgrade) keeps me occupied so I do not notice the slightly higher revs of the engine! Due to the higher revs, I fully expect a increase in fuel consumption though but worth the performance boost.

Below are some pictures of the process. I bought an extra full final drive unit from BMW and had it modified with the Quaife and gears first.

Gears I obtained through Bimmerworld here -- https://secure5.nexternal.com/shared...t=products.asp.

Literally searched the world over (literally) for 3.64 gears at a cheaper price but they are difficult to find. The OEM gears for the Z8 are a 3.38 ratio and a 215k size (215 is the outer diameter of the ring / crown gear, the k refers to a short but fat pinion / beazel gear. The e39 M5 (same s62 engine and transmission as the Z8) uses a 210 gear with a standard pinion, hence, no k designation. The 3.64 215k gears I could not find a BMW part number for in order to order them direct so if you want them, you HAVE to go through a reseller like Bimmerworld above to get them. Every source I found list the gears at an average of $1800 usd. Bimmerworld lists them for $1795 (the cheapest found).

Here is the kicker -- the 3.64 / 215k gears are EXACTLY the same gear used in the e65 735i in Europe as well as used for a short time even in the X5. The Differential / final drive is the same large differential internals used for several years in the e65 7-series and BMW modified the housing and cover so it would fit the Z8. A complete final drive to fit the e65 735i should cost around $1400 including gears. You could buy this and harvest the gears but even though it is EXACTLY the same gear and would fit the Z8, EVERYONE upcharges the gear if you are going to put it in the Z8. That really burns me up. BUT, for now a necessary evil if you want the 3.64 gears for your car.

The only solution to prevent that upcharging is to discover the official BMW part number for the 3.64 / 215k gears for the e65 735i (the BMW part number for the whole final drive is 35107514990 but the part number for the gears I have not been able to find out), which I continue to work on in my spare time but this is very difficult to find out, unless you are in the differential business with BMW.

Another source for gears for the Z8 is Dan's diffs on-line here:

http://www.diffsonline.com/product/customdiff5.htm

Dan Fitzgerald is a nice and helpful guy, but a little pricey. He will do the work himself and turn the diff around quickly. He can get the gears you need, and he also has a Salisbury clutch style LSD he can fit into the diff for those of you who do not want to purchase a Quaife. This does require modifications to the housing.

One note here is, regardless of who you purchase your gears from, do not believe them when they tell you that these 3.64 / 215k gears are specially built by BMW Motorsport for the Z8. There is no such animal. The 3.64 gears are straight from the e65 7-series and manufactured by BMW AG, just like all the other parts on the Z8. This "Motorsport" I think name was used as a sales tactic to justify the higher price.

I had my diff rebuilt by Jim Rowe at the Metric Mechanic, Richland, Missouri. The link is here:

http://www.metricmechanic.com/

He was close to where I live, and therefore accessible if there was a problem. Local BMW Club people recommended him to me and I found the experience to be a good one. Jim and his wife Mary, were very accomodating and the price was reasonable. I supplied the Diff, gears, and Quaife and he rebuilt it for $1200 including shipping everything back to me overnight.

A few specifications of the rebuild -- some of these numbers will vary slightly as there is a range.

Break away torque (main bearing) - 10 pound / ft.
Backlash clearance -- .004
Rolling torque:
Pinion bearing - 20 pound/ft
Total torque - 26 pound/ ft.


The gear oil recommended by Quaife is a 75W90 Fully Synthetic gear oil. They recommend Silkolene brand but I was unable readily find a vendor in my area so I went with Red Line Gear lubricant. Red Line has a long tradition of motor, transmission and gear lubricants for street and racing applications and is readily available. At this point I plan to perform the 1200 mile service and change the lubricant at that interval just as was recommended when the diff was new.

Now on to having some fun!

A few pictures of the process:

[dwz8]

Hi Jeff,

congratulations! I still remember that impression when I made the exact same mod. The Quaife (or equivalent diff) was probably the most important change after the tires, the change to 3.64 is the icing on the cake.

So from your post I take it that you paid about $1,200 (assembly) + ~$ 1,800 (gears) + the Quaife (?) ?
So it looks like the former offer from Koala was reasonable, too.

Have fun!

[Z8doc]

Brett with Koala is similar except he charges more for the differential if you keep your original and refunds about $1495 if you send the OEM back to him. I wanted to keep my original as a spare and I wanted to use the Metric Mechanic as they are closer geographically in case of a problem.

I did contact alot of folks about rebuilding the diff and many of them stated they could but in reality, they were more expensive than Brett or the Metric Mechanic as these other people were just going to take the diff, send it to Brett, have him rebuild it, then send it back to me after and Upcharge the whole process like a handling fee. I even received an email from Brett when I was searching that stated that "I am afraid that whoever you send your differential too, I will be the one rebuilding it" because many of the people I got quotes from contacted him for a price. That statement I thought was sort of arrogant which drove me to find who else does this kind of work, as I could not believe there was only ONE person in the USA to rebuild a BMW differential. Clearly there are options. I only listed a few in my post.

For example, a good option for you folks in Europe is Drexler Motorsport
www.drexler-motorsport.com who has a Clutch LSD for the Z8 and 3.64 gears available. Ask for Timo Heinen. They were willing to rebuild mine and put in the Quaife, similar price too. Just too far for me to ship my diff but if your are in Europe, maybe a good choice. Another choice that Dieter gave me is Oliver Nowack at Nowack Tuning. The link is:
http://www.nowack-tuning.de. They work exclusively on Z8 and race them as well and have mulitple gear sizes available.

The Quaife I have is a special design and there are some issues with Brett having access to this particular Quaife. Hence, part of the reason I was looking for someone else to rebuild the diff since I had no one in Oklahoma who was competent in doing the job.

Just now, I am looking forward to some more seat time as it warms up here!

[Dogsbreath]

Hey Deiter

I am working on getting some gears - it may prove cheaper. If it turns out to be viable I will post it on the site.

Dave

[thegunguy]

Those are some great pics of the build up process at Metric Mechanic - you can really see the reduction in weight on the Quaife versus the OE diff. I have my remanufactured final-drive, Quaife, and gears boxed and ready to ship to Metric. Just a few more weeks...

[thegunguy]

I don't think I've been so excited since the day I got the car. My completed final drive with light-weight Quaife and 3.64 arrived yesterday after build-up by Metric Mechanic (see the Doc's pics and narrative in a previous post). Now I just have to wait until the 16th when it goes in the shop.

As mentioned in another thread, I'm having the clutch checked out for slipping. If it's toast, I'm going with the UUC/BMW 850CSi clutch and light fly-wheel. It was a hoot in Dieter's car!

All should be ready for the run to Santa Fe.

[thegunguy]

Can't really add anything to Jeff's review. What a "diff"erence!

[Z8doc]

I have had the Quaife and 3.64 gears in my Z8 now for about 5,000 miles which includes local driving and the MITM trip to Santa Fe.

Overall impression is still the same.... IMHO, BOTH are a MUST upgrade.

The 3.64 is about an 8% gear change that you definitely notice everyday in the seat of your pants. I have not noticed any significant difference in gas milage in town or on the highway (although gas prices have gone up nearly 50% ). Although the desire for "pedal to the metal" is more!

The Quaife is a more subtle upgrade but a MUST. I really did not appreciate it until the MITM trip to Santa Fe. Before the Quaife, during hard cornering and hard acceleraton, the DSC came on frequently and IMHO, was a performance restrictor and deterrant. Now that I have the Quaife, I have noticed the DSC actually activates significantly less. After thinking about it, this makes sense as the purpose of the Quaife is to transfer traction to the wheel that has the least, thus decreasing wheel spin -- which is precisely what DSC monitors. Further evidence that BMW SHOULD have put a LSD in the Z8 in the first place IF they truly had intended "Ultimate performance" for the Ulitmate Driving machine.

Anyway, both are a MUST and I they definitely enhance my ownership experience.

[fun2drive]

& helping to make up my mind to install the Quaife w/3.64 gears. I plan to change out the CDV & install an Eisenmann race muffler at the same time (2/3 received), but only after my cutie has the "performance package". I plan on keeping all my old parts, just in case . . .
Question: Any advice as to whether I should do ANY mods seeing as my car is an "Individual" Z8? Maybe I can find a local car collector or evaluator who may also help.
Thanks for any feedback,
Evie

[macfly]

but in the fullness of time the mods that are considered as serious enthusiast upgrades, not badly thought out or engineered parts, will be a definite value add to any collector. I am confident that a Z8 with the 'Performance Upgrade', an LSD, CDV delete, Eisenmann, short shift kit and Dinan swaybars will be considered 'properly prepared' and not 'hacked up' or 'chopped about'.

I could well imagine that in a Barrett Jackson, Christies etc catalog in 2020 these additions being described as the 'essential upgrades' or 'correct enthusiast package' much the same way as properly prepared E Types with the correct aftermarket upgrades are considered very desirable.

An untouched car may be worth more, but only if it has very few miles on it, thus the conundrum of classic car ownership, to drive, and depreciate your investment, or to mothball and preserve it. If you bought the Z8 to drive then you want to make the miles you put on it as satisfying as possible, thus I'll be doing the right upgrades to mine.

At around 2000 miles a year by 2020 my car will have done about 40K, so it won't be worth what a mint 2000 mile car will be in 2020, but I bought it to do drives, events and rallys like Meet In The Middle.

If you are looking for a long term investment I'd suggest art, it appreciates much faster, and you don't have to go to the garage to enjoy it! I've had around a 1000% ROI (yes - one thousand) on the art I bought in the mid '80's, there is no car or bike that could come close to equalling that.

[Z8doc]

do what your screenname suggests about your 'individual Z8" fun2drive!

All the mods listed are considered essential - if you going to modify - to just about everyone on this board, even though several may not have performed them... so I agree with Macfly that these mods will not detract and more than likely add to the value of the Z8 in the future (when comparing a 60K 2001 stock with a 60k 2001 modified as listed in the year 2020).

Enjoy your Z8 is my motto so have fun!

Hmmm, if I stop driving mine altogther right now Mac with 39K miles, by your calculations in the year 2020, you will catch up to me at that point.... wow, I just do not see myself doing that but I suspect that overtime, I will drive mine less and less and eventually only to drives and ralleys, so most likely when we are old and grey -- maybe our Z8s may have the same miles on them, like say when we are both about 80 years old!

[fun2drive]

My Z8 will get the 3 mods (LSD, CDV delete, Eisermann) as soon as the "Performance Upgrade" is in. At that time I'll see what's left to do on the front end (swaybar may be part of the pkg, only BMW knows for sure).
The short shift kit is a mystery to me & have begun researching it.
Andrew, Jeff, thanks to you both! Can't wait to do the Perf. Upgr., the mods & enjoy the car again!
Evie

[macfly]

as they really eliminate both bad understeer and bad body roll in quick transitions. I'd honestly say that doing the swaybars is the #1 upgrade in terms of improving the car. The short shift kit is bt UUC and reviewed on the site too.

[thegunguy]

As a fan and one of the "charter members" of the "light-weight" Quaife club, I have been very pleased with the upgrade, not to mention most of the other mods mentioned here, but I firmly believe that ditching the RFTs is the absolute best modification that can be made. The bang-for-your-buck factor is without equal, and the reduction in shock-tower destroying mass is priceless.

[jdillane]

...is how my 2001 Z8 remains but thanks to this immensely useful blog, I have a good idea where to start re enhancement, once I save a few bucks.

Having acquired my Z8 as an investment (and a tax shelter!), I was early on advised that driving the car would help preserve her rather than hinder. I saw no point in arguing as she is such a pleasure to drive. I am now a couple hundred miles shy of 10K and I can only hope that the issues many of us have experienced so early on will not find themselves in good company with a new set of problems.

I happen to come from relatively modest means so I was quite fortunate to acquire my car. Short story: My grandfather was a zealous collector of old cars (reputed to have amassed between 600 and 1000 cars) and it came to pass that 1/2 of one of them was given to me on condition that it be sold. Since the basis in the car, a 1924 Mercedes, was so low, I faced a significant tax burden as the car was worth quite a bit now even as a 50 y/o restoration. So, last year I traded my 1/2 interest via IRC 1031 and avoided the tax. My wife is not happy about it but she could not argue the tax issue. Bonus: she has yet to ask to drive the Z!

Living in MI, I am a couple of weeks from putting her away for the winter. Aside from the trickle charger, is there anything critical I should do to her in prep for storage?

[macfly]

is there anything critical I should do to her in prep for storage?

leave all the doors, trunk, hood and soft top slightly open so as to preserve the elasticity of the rubber seals. It is always better to change all the oils and hydraulic fluids before storing a car, as you'll remove any water or oxidants that have got into the fluids. Also I'd recommend over inflating the tires by 15psi. Finally make sure you put it in a sealed and dry spot.

[macfly]

You can fit a standard Quaife LSD into the final drive of the Z8, which is precisely what Brett Anderson did and what got this whole movement started as some of us did not want to modify the housing for fears of weakening it. This group buy was for a special designed lightweight Quaife that was made to fit the Z8 final drive housing without modification.

The standard Quaife that Brett at Koala Motorsport uses is the one that will fit the 540i, but REQUIRES the milling out / modification of the inside of the housing so that the standard Quaife will not rub or make contact with the sides of the housing. This theoretically could weaken the final drive housing but those that have had this done, they report no problems so it is probably a viable alternative. He carries the 3.64 gears too.

Another source for gears and a Salisbury type LSD (clutch style with variable % of limited slip) is the Metric Mechanic. I used them for the installation of my Quaife and they have a Salisbury type LSD that they can fit into the Z8 housing, but also REQUIRES modification of the housing to make it fit on the inside. They do excellent work and I recommend them highly. They do not carry the 3.64 gears however. You would have to get those from another source like Bimmerworld. Both Brett and Bimmerworld sell the gears for $1800.

For those in Europe, a good source for an LSD would be ordering directly from Quaife a differential (they may be able to sell the lightweight one to you without violating design rights and marketing rights like us in the USA have to do) or.. a great alternative is to contact Drexler Motorsport. They make a Salisbury LSD with variable limited slip that will fit the Z8 WITHOUT modifying the housing. They also carry the 3.64 gears. Their website is here (look under propulsion technology). Someone in the USA can use them as well but expect delays sending and getting your diff back due to custom checks but they have a top notch reputation.

Hope that helps to anyone else in the need....


Thanks for the info.

[Z8Eldred]

Just installed the Salisbury unit in my Z8 and like all of those before me, all I can say is wow. No more spins when accelerating out of corners and more eisenmann exhaust growl, stability and less DSC intervention.

The car should have come with LSD...

[macfly]

You are the first one to have a Salisbury type LSD installed. I'm curious why you chose this unit over the Quaife LSD that the rest of us went with? It uses friction plates which in the long term are prone to wear, meaning that this is a unit that requires periodic adjustiments. I am not sure how easy or hard that is, but it always seemed to be just one more thing to think about.

Here is a good link to a site that explains the differences very clearly. Here are a couple of diagrams to compare with the Quaife unit shown above.

[Z8Eldred]

You are the first one to have a Salisbury type LSD installed. I'm curious why you chose this unit over the Quaife LSD that the rest of us went with? It uses friction plates which in the long term are prone to wear, meaning that this is a unit that requires periodic adjustiments. I am not sure how easy or hard that is, but it always seemed to be just one more thing to think about.

Here is a good link to a site that explains the differences very clearly. Here are a couple of diagrams to compare with the Quaife unit shown above.

The Salisbury unit in my Z8 was made by Brett Anderson at Koala MS.

I considered several reasons when choosing the Salisbury over the Quaife. Three reasons solidified my choice.

My first two reasons are availability & widespread use. The Salisbury costs the same as the quaife in the Z8 application, but it is more widely used and proven in the E39 and E60 Five series cars and was more readily available for purchase (on the shelf at the time of purchase). The use in my Z8 was not a technical prototype, simply an application of the existing Salisbury LSD's used in the Five Series cars being modified to work in the Z8. I am presently having another Salisbury unit installed in my E39 540I6.

My third reason was that the Salisbury unit uses the same design or reaction as the quaife while employing 40% Static Lock, unlike the Quaife which does not have static lock and would behave like an open differential when lifted or on ice.

I spoke with Brett Anderson after reading your question and he confirmed that you are right about the unit's possible wear in the long term but this term is a minimum of 200K miles of street use and varies with owner care & maintenance. However, he stated that there are 'no' periodic adjustments needed for the life of the unit.

Around this mileage should the owner notice any problems, Brett suggested two available options: have the unit refreshed for $1500 or obtain a new one off the shelf.

I knew all of this going in, but I was sold on the features of the unit, its long life, no maintenance and the easy availability of parts now and in the future. I did not want another unique hard to obtain part on an already rare vehicle.

I am not concerned about the 200K mark in my Z8 ( I am currently at 12K in my 2001), I am more concerned about the availability of parts, should I break the unit prior to or after that point.

I did not want the car to sit for six months waiting on a broken mechanical part that I chose to put in.

Both the quaife and Salisbury work in this application, I just didn't want to wait six months for the quaife and selected the Salisbury after pondering all its attributes.

[Z8doc]

I chose to buy an extra Quaife, to keep as a spare should I ever need it. Granted -- it IS an expensive piece of internal Jewelry to have just sitting around but as you said, as time goes by, parts... whether OEM or aftermarket... are just hard to come by so, since the Quaife was a special order, I thought best to have an extra.

The Salisbury units are proven units and many racers use various amounts of % lock up and depends on your needs. Most OEM LSDs, like the ones in the e39 M5, my 1988 M6 have only about 15% lock up and is static. There are Salisbury units that have a variable amount of % lock up too and can be fitted, just as yours was, with modifications to the housing internally. See www.metricmechanic.com for such a unit if anyone is interested. Ask for Jim Rowe.

Oh, yeah -- the Wow feeling from the LSD is an understatement, especially if you got the 3.64 gears at the same time!

[thegunguy]

Take it to a track where you can really enjoy the improvements from the LSD.

Oh, and I have spent many sleepless nights worrying about the inability of my Quaife to perform on ice!

[Z8Eldred]

LOL. Point Taken.

[Bend]

It's time to change the Quaife Differential oil. Redline is clearly preferred. The question is what is better - the 75W-90 or 75W-140?
The 75W-90 is recommended for the standard Z8 differential and I know that a number of us use that in our Quaife differentials. I can't find any mention on the site of the 75W-140, yet Turner Motorsports and other sites recommend the heavier 75W-140 for the limited slip Quaife. Does anyone have any thoughts or experience with this?
Thanks.

[Bend]

Think I can answer my own question after some investigation. Turns out that the majority of sites (E39 and Lotus included) recommend the 75W-90 (Usually Redline) for the Quaife LSD, unless it is for a racing application, in which case the 75W-140 should be used. If someone can confirm, this might be useful for others in the future.

[Z8doc]

Think I can answer my own question after some investigation. Turns out that the majority of sites (E39 and Lotus included) recommend the 75W-90 (Usually Redline) for the Quaife LSD, unless it is for a racing application, in which case the 75W-140 should be used. If someone can confirm, this might be useful for others in the future.

:thumbs: Ted, that is exactly what I understand about it. The 75W-90 is what Quaife recommended for daily performance driving (including the occasional autocross or track event) when I did my original research on Diffs and gear changes. The 75W-140 is for racing applications, which we really do not need or require as I am sure none of us "race" our Z8s!!!!

[Dogsbreath]

:thumbs: Ted, that is exactly what I understand about it. The 75W-90 is what Quaife recommended for daily performance driving (including the occasional autocross or track event) when I did my original research on Diffs and gear changes. The 75W-140 is for racing applications, which we really do not need or require as I am sure none of us "race" our Z8s!!!!

My reading indicates that BMW switched to 75-140 for the M3. I really dont see a downside to a higher standard (other than a theoretical slight increase in drag)
My BMW fanatic friends at Sincity BMW recommended 140 with the caveat to make sure it has the antislip additives. They generally use Redline. I trust them. They never steered me wrong
I'm running 75-140 with no issues

Davep