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Thread: The dreaded 1st-2nd shift

  1. #1
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    The dreaded 1st-2nd shift

    I don't know about the rest of you, but I have always found the shift from 1st to 2nd gear in the Z8 to be awkward at best. Removing the clutch delay valve does help a little but doesn't eliminate the problem. I now believe the real culprit is the self adjusting clutch design BMW uses in its LUK sourced pressure plates. These are meant to adjust the clutch disengagement point over time to compensate for wear. I think their real purpose is to make drivers feel like incompetent boobs! These self adjusting clutches can also lead to premature clutch failure due to slippage and provide a mushy feel to the engage/disengage process. I recently began experiencing clutch slippage in my driver Z8 and upon removal, discovered that the disc was barely worn and not contaminated in any way. The problem was in the pressure plate's self adjustment feature. Not wanting to repeat this situation, I installed a higher performance, non self adjusting, disc and clutch sourced from UUC Motorwerks and miracle of miracles, the dreaded 1st to 2nd shift is now buttery smooth! On top of that, overall clutch feel is greatly improved with smooth and predictable take up at all rpms. I chose their Segmented Kevlar Clutch Kit which is a direct replacement for the OE clutch in the Z8. It does provide substantially higher clamping force so it is suitable for use in cars with increased power but doesn't increase the pedal force required for operation. Assuming you have the dual mass OE flywheel or the Dinan lightened dual mass flywheel, you want to order the solid hub clutch disk. If you have a one piece light weight flywheel, you should order the sprung hub clutch disk. The kit comes with a new throw-out bearing and a disc centering tool for $795.00. UUC offers a variety of clutch kits but I think this is the best one for street and occasional track work. If you have further questions, I suggest you speak with Rob at UUC (908-874-9092) www.uucmotorwerks.com.

  2. #2
    Administrator thegunguy's Avatar
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    Yes, the 1st to 2nd shift has always been a bit awkward.

    A new clutch and flywheel is on my "to do" list. Well, it's been there for a while, as I will often get slippage when really pouring on the power when shifting 2nd/3rd/4th. I've been interested in the the adapted 850CSi package as it I like the ability to maintain via BMW's parts catalog, and it has ample needs for my stock engine. However, all the stories of chatter with UUC's lightened flywheel has kept me from "pulling the trigger".

    Lately, I've had my eyes on the Dinan dual-mass flywheel, but that means I'm just going back with the standard clutch that will likely wear out at the same rate. I guess I had not considered using the Dinan flywheel with the UUC clutch. From your post, it sounds like this a "doable" combination.

    Which flywheel are you running, and if it's the UUC, how's the noise?
    thegunguy

  3. #3
    The 1>2 shift has been notchy on all four of my Z8's, so I'm happy to hear that you've discovered a way of getting around it. I will certainly do this upgrade to my driver at it's next major refresh.

    On the subject of gears there is one other thing that has always bothered me on twisty canyon roads I am always finding that the revs step between 2 & 3 is too great, you jump from screaming to lugging, so I'd like to make second gear closer to third. Any thoughts on doing that GM?
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

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    3.64s? More screaming to less lugging.
    thegunguy

  5. #5
    Changing the final drive ratio won't alter the spread between 2 & 3, though it might lower the overall gearing enough to keep you out of 2, however as you know I really like the lazier final drive ratio, and kept mine stock when I put the Quaife in.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

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    In my Z8 with the Daytona Prototype motor, I use the UUC aluminum flywheel and their 850CSi clutch package. I really like this combo and if you use Red Line fluid in the tranny, there really isn't any noticeable gear lash noise, except outside the car at idle, and even then it is barely audible. The extent of gear lash noise could vary from one car to another as a result of transmission wear differences so your experience could be different but this UUC package is designed to minimize, if not preclude, gear lash noise through the use of a sprung hub clutch disc. In my driver Z8, I have the Dinan dual mass lightened flywheel mated with the UUC Segmented Kevlar Clutch Package, which does not exhibit any gear lash noise whatsoever. Both packages are highly recommended. By the way, clutch slippage is most likely to show up at wide open throttle in the higher gears and my guess is your clutch is not worn out, just misadjusted, as a result of the self adjustment feature.

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    Administrator thegunguy's Avatar
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    Do you know if the 850 clutch can be used with the Dinan flywheel? I really think this would be the best of both worlds.
    thegunguy

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    I do not believe the UUC 850 clutch is compatible with the Dinan flywheel since they use a sprung hub clutch disc which is not appropriate on a dual mass flywheel. Also, the Segmented Kevlar Clutch Package offered by UUC is lighter in weight than the 850 clutch and therefor will provide a lower mass benefit. The reason they use the heavier 850 clutch with their aluminum flywheel is because it is a better match for such a light weight flywheel. You should know that Dinan also offers an even lighter weight flywheel and a special clutch package which is an alternative to the UUC aluminum package, but it is known to be quite noisy for street use. For those who aren't familiar with the benefits of a lighter weight flywheel, let me explain. OE flywheels are usually made from steel and are usually very heavy. That weight provides damping for engine impulses, a high moment of inertia to help launch the car from rest, and helps absorb gear lash noise from the transmission. Unfortunately, that weight also slows down the acceleration rate of the car as well as the responsiveness of the engine when you blip the throttle to match revs during downshifting. By milling material off of the flywheel to lighten it (Dinan) or by switching to a lighter weight material like aluminum (UUC), the car's acceleration rate can be improved, particularly in the lower gears, and when you blip the throttle for a downshift, the engine's response is much faster. The primary drawback to reasonable lightening of the flywheel is the increase in noise from the rotating gears in the transmission known as gear lash. This is only audible at idle, with the clutch engaged and the transmission in neutral. If the car is moving or the clutch disengaged, gear lash noise is no longer audible. Dinan's lightened flywheel is still heavy enough to absorb most of the gear lash noise so it really isn't an issue. UUC's aluminum flywheel is considerably lighter than the OE flywheel and as a result, gear lash noise would be objectionable for street use. Fortunately, if you use a sprung hub clutch disc, you can minimize that gear lash noise to the point where it is barely audible and that is what UUC does. There is another way to improve engine performance without necessarily decreasing weight and that is by reducing the diameter of the flywheel and clutch assembly, thereby decreasing the polar moment of inertia of the rotating mass. This has the same beneficial effects as removing mass. Unfortunately, it has another drawback which is a decrease in the surface area available for coupling the clutch disc with the flywheel and the pressure plate. As a result, to get adequate coupling friction, higher spring rates must be employed in the pressure plate resulting in a higher level of clutch pedal effort and a less progressive engagement. In a race car, a combination of lighter weight and smaller diameter components is often employed to gain maximum performance benefits. This same approach was used by Porsche in its Carrera GT street car which is why so many owners dumped the cars after only a few miles of driving: the clutch was essentially on/off and tricky to use on the street. Hope this helps.

  9. #9
    Z8 Ate My Homework! Norcal's Avatar
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    Quote Originally Posted by macfly View Post
    The 1>2 shift has been notchy on all four of my Z8's, so I'm happy to hear that you've discovered a way of getting around it. I will certainly do this upgrade to my driver at it's next major refresh.

    On the subject of gears there is one other thing that has always bothered me on twisty canyon roads I am always finding that the revs step between 2 & 3 is too great, you jump from screaming to lugging, so I'd like to make second gear closer to third. Any thoughts on doing that GM?
    I find the same thing, but 3rd is so great the way it is. I would make 1st longer, as it is almost useless now, and take 2nd closer to third.

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    I totally agree with Macfly's and Norcal's comments on gear ratio spread. On a race transmission, the suggested changes would be easy to accomplish but I'm not sure the transmission in the Z8 would accommodate different ratios. I will try to find out. In the mean time, try starting from 2nd gear and see what you think about that ratio for 1st gear. An interesting trend in high performance cars these days is to have first gear long enough to get the car to 60mph. This is to maximize 0-60 times which have become a benchmark for performance comparisons. Currently, a Z8 with OE differential gears and running stock diameter tires, will reach 39mph at redline in 1st and 65mph at redline in 2nd. If you have installed 3.64 gears, 1st takes you to 36mph and 2nd takes you to 60mph, which might be ideal. See what you think.

  11. #11
    Carter Carter Rise's Avatar
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    The take up point on my clutch is now almost at the floor, so I suspect that the self adjusting pressure plate is the culprit and it's time has come. Given this thread is now 9 years old, are we still recommending the segmented Kevlar clutch kit and the Dinan dual mass lightened flywheel? The car has the Dinan software, but the drivetrain is stock otherwise.

    Any thoughts would be appreciated.

  12. #12
    Quote Originally Posted by Carter Rise View Post
    The take up point on my clutch is now almost at the floor, so I suspect that the self adjusting pressure plate is the culprit and it's time has come. Given this thread is now 9 years old, are we still recommending the segmented Kevlar clutch kit and the Dinan dual mass lightened flywheel? The car has the Dinan software, but the drivetrain is stock otherwise.

    Any thoughts would be appreciated.
    How many miles on your car? Has anyone else experienced similar issue(s)?
    Skip Hammerman

    2002 BMW Z8 - Meisterschaft GT, PP installed, CDV delete
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  13. #13
    Administrator thegunguy's Avatar
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    Quote Originally Posted by Carter Rise View Post
    The take up point on my clutch is now almost at the floor, so I suspect that the self adjusting pressure plate is the culprit and it's time has come. Given this thread is now 9 years old, are we still recommending the segmented Kevlar clutch kit and the Dinan dual mass lightened flywheel? The car has the Dinan software, but the drivetrain is stock otherwise.

    Any thoughts would be appreciated.
    My plan was to go with the UUC clutch/flywheel derived from the 850CSi. It's a better fit for the power of the S62 without going overboard, but what I really like is the simplicity of future maintenance. Since the kit is using the serviceable components from the V12 850CSi, parts should be more available than some lower volume aftermarket clutch.

    http://store.uucmotorwerks.com/ultim...d-z8-p268.aspx
    See the 'Standard BMW Clutch' option
    thegunguy

  14. #14
    Administrator thegunguy's Avatar
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    Quote Originally Posted by Musta10000 View Post
    How many miles on your car? Has anyone else experienced similar issue(s)?
    The original self adjusting clutch hides its wear, and it's definitely under-gunned for the Z8 and the E39 M5.
    thegunguy

  15. #15
    Carter Carter Rise's Avatar
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    13,000 miles. I am the original owner. At 47 miles, the car wouldn't go into gear. They found the pressure plate bolts were loose, so we got a new clutch, pressure plate and release bearing in the first month of ownership.