Quote:
Originally Posted by Blind32
Thanks all.
Well, 2 grinds yesterday  I've put about 150 miles on the car. I miss the way it sounded before. It is tolerable below 5k, but above that, it sounds different and I miss the old sound of the engine. The new vibration sound drowns out the beautiful music of the S54 at high RPM and didn't fix my issue of grinding. I'm sure the neoprene won't change the sound much, if any.
Both times I grinded, I was doing everything correctly. I now believe this issue is just something to do with the high rpm and the tranny. I don't know anything about the inner workings of transmissions so I won't even begin to guess. |
Bummer about the 1st-2nd issue. I'm coming to agree with Jragan and inTgr8r that the 1st-2nd grind is a separate issue from the denial of 3rd to 2nd. As inTgr8r put it in one post....
There are three separate issues:
a) 1-2 grind which is tranny design/synchos; other fluid may help RP Synchromax, Redline MTL etc.
b) Downshift to 2nd gear rejection under loading conditions. = tranny mounts
c) Clutch engagement feel = CDV
I've read, or think I've read, that the transmission in the ///M is actually from the regular Z4. If that's the case, it may have never really been designed to handle the higher-revs the ///M throws at it. The two times I've had "grind" were shifting at high RPMs--and that's where maximum torque with this engine lives as well. I really think this points to an internal design flaw--or more likely a design deficiency (they didn't build a transmission spec'd to this motor).
I hope the tranny mounts help with issue "b", but I guess we won't have definitive data on that until someone who has had issues tests the new mounts under the same conditions.
My solution, for now, for the 1st-2nd issue is to shift earlier into 2nd. Not ideal, but I don't really see this as a drag-racing car, and the only other place it could present an issue is launching in autox. And I can't recreate it easily--it's happened very rarely.
If you want to test option "a", you might be a good candidate to try that. I can't recreate the grind that easily but sadly it seems you can, so your car may make a good test subject....