Driveshaft Issues

[Brandon12V]

Ok I don't know what the fuck is going on but I am burning through CSB's like I can't understand. Driveline set up is like this....
Solid aluminum motor and trans mounts
Ertalon subframe bushings
aKG trailing arm bushings
VAC Delrin diff bushing
Rev shift billet guibo
Rebuilt driveshaft(TWICE)
Stage III Southbend clutch
Jb racing aluminum flywheel.....

Everything is tight as a virgin yet somehow I am going through center support bearings every 6 months. What the hell is going on???!? I haven't done Autox or any kind of racing event in the 2 years. I drive my car standard. No street racing crap. Just standard daily driving. Thoughts? This is stumping the shit out of me and all I can think of is the driveshaft shop is not balancing true.

[Brandon12V]

I'll also mention I've had the axles rebuilt. And replaced wheel bearings... Though that shouldn't really matter. It's also starting to take a beating on my transmission from all the vibration and I fear it will need rebuilt within the year. I've already had to replace the input and output shaft seals.

[jlevie]

Are you using a Drive Line Services (or equal) rebuilt? A shop that doesn't have a lot of experience with BMW drive shafts may not be getting it right.

I'd say to get a rebuilt from Drive Line Services (or Bimmerworld), go back to an OE guibo (the rev shift may be too stiff), and replace the motor & transmission mounts with AKG poly parts.

[Stanley Rockafella]

go back to stock everything since you dont race it anyway.

[Brandon12V]

Yes because I'd love to have squishy bushings again.. Looks like this time it wasn't just the CSB...

[jw 325ic]

get a bmw flex disk and have the u-joints replaced. problems solved.

[Brandon12V]

Revshift is sending me replacement bushings and new hardware, staying true to their warranty. Good guys.

[Brandon12V]

Dude... I've had the u-joints replaced. In my post above I even stated the driveshaft has been rebuilt....twice.

[jw 325ic]

lol its a drinking at home night...what can i say? thats pretty sweet about revshift staying true to their word but ive never used one, only oem, and theyve lasted for years. kind of crazy though. id double check the ujoints man.

[Brandon12V]

At this point I think I'm gonna have check the ujoints cause theyre probably all sorts of fucked up now, lol.

[Cephas]

I wouldn't trust a remanned driveshaft. It costs extra up front to buy new, but you know for sure that it's balanced - and, let's face it - it would have been cheaper to go new at this point...

I just replaced mine with a new one to cure a vibration above 4k under hard acceleration. All the research I did (including posts here) said to go new. Good luck.

[jlevie]

In my opinion, the cause of this series of failure is the complete elimination of "squish". When you take all the resiliency out of the power train and supports any alignment errors transfer loads to other parts of the assembly. Those parts were never meant to see those sorts of loads, and they fail.

In this case the quibo is good example. It is there to allow for slight alignment errors between the drive shaft and transmission. If you remove that resiliency, the loads transfer to the bolts (which fail). In a like manner, using aluminum motor and transmission mounts transfer loads to the drive shaft. In a perfect world the engine, transmission, and final drive would be perfectly aligned allowing for rigid mounting and the chassis would not flex at all. But manufacturing isn't quite that good and the car's chassis isn't that stiff (it flexes). So some give is needed through out the system.

The other issue I have with rigid motor/trans mounts is what they might do to vibrational modes in the engine. While six cylinders is one of the two IC designs with the best internal balance (a boxer is better), there are still vibrations. And the engine will have resonances that can change if you rigidly mount the engine. What that might do is anyone's guess, but there is plenty of evidence to show that the OE type mounting (with some resiliency) doesn't create issues. Arguably, the OE mounts were chosen for ride quality and stiffer mounts can be profitably used. But rigid may be too much.

[Brandon12V]

I agree Jim. They ARE race mounts for a reason and you're right. The e30 was designed to have more frame flex than I originally knew of before I bought new mounts. The whole idea behind me purchasing VAC mounts was bc I'd never have to replace them again at the drawback of other mount failures but I didn't realize it would play this critical of a failure. I may be a guinea pig for a Jay Racing shaft ( http://www.jayracing.com/index.php?m...oducts_id=8076 ) as I cannot find any current reviews on their product. I've tried contacting them to see what warranty they offer but if none is given, I will be going with new oem and trading my engine/trans mounts out for something more... subtle in nature. For the record, my driveshaft balance was only $89.99 (with new u-joints) per shot so it wasnt that much of a loss, all expenses considered.

[jlevie]

If this is a pure race car I'd use AKG 75D poly motor/trans mounts, but if primarily a street car that only sees occasional track time I'd use the 80A mounts and if purely a street car the OE mounts. While the Rev shift quibo is pretty cool, I wonder if it is too stiff. I can say that the OE quibo holds up nicely on a Spec E30 that sees lots of race time every year.

If the car was mine, it would get a Drive Line Services or Bimmerworld reman drive shaft. I don't know who Bimmerworld uses for their drive shafts, but I know the part has a very good reputation. A quality reman is cheaper than a new one, though that is an option.