New CSB and Flex Disc but still have vibration

[Rojoryu]

I had a horrible banging in 1st and 2nd gear under heavy acceleration. The CSB was shot so I replaced that at the giubo with fresh ones. I also took the driveshaft to a local BMW race shop and had it inspected. Just took it for a test drive and it is much better but I am still getting a vibration in first gear when I floor it. Where should I look next? Or is it possible I didnt install something correctly?

Thanks in advance.

[Rojoryu]

Yeah so, I had looked at a few pics before installing the csb to make sure I had it facing the correct way in relation to the splines on the DS. I think those may have been pics of e36 DSs. If I did install it backwards could this be causing the issue? I also didnt pre-load it.

[TobyB]

First gear floored isn't a preload issue, it's a torque windup thing.
Or alignment.

I'd look at that first, then your diff, trans and engine mounts.
Also the slip joint- it needs to be loosened to allow things to align,
then snugged pretty tight afterwards...

hth

t

[Rojoryu]

First gear floored isn't a preload issue, it's a torque windup thing.
Or alignment.

I'd look at that first, then your diff, trans and engine mounts.
Also the slip joint- it needs to be loosened to allow things to align,
then snugged pretty tight afterwards...

hth

t

Thanks for the response. I'm going to ask some questions that will highlight my ignorance. But if I knew everything I would be here asking in the first place, lol. What is torque windup and does that imply its normal or represents another driveline issue? If I did install the csb backwards, would that cause an alignment issue? I am out of town but will definately check mounts (motor mounts are new). I only tighnted the driveshaft nut by hand. I will tighten it with a wrench and report back.

[TobyB]

Torque windup is just a fancy way of saying that things move around when you
put a lot of torque on them. And if the center slip joint's loose, that might
let things move more than they should. I don't THINK you can install the CSB backwards,
but on the (late?) car you might. It's been a while since I looked, but I remember
that it'd be pretty obvious... but I might be wrong about that...

t

[uturn]

Dealing with a driveline issue myself...replaced the csb and still felt a faint vibration. Confirmed that my u joints are on their way out.

[Rojoryu]

Yeah, I'm starting to think it may be the diff. Motor and transmission mounts are good, diff mount could be better but isn't horrible. Could be the clutch packs maybe, I don't know. Could also be the driveshaft, I just don't want it to be, lol.

[jlevie]

What you describe sounds like a classic description of binding u-joints in the drive shaft.

[Rojoryu]

It was in fact the driveshaft. I purchased a previously rebuilt one with serviceable u-joint and installed it. Problem solved. Thanks for the help.