*RESOLVED* 2k to 4k rumble/vibration 2nd gear

[siamkazi]

Hey everyone, have been chasing this fun problem for a few weeks, just changed out the CSB and now there's a rumble/vibration from 2.5k to 4k in second gear, other gears seem fine, a little bit in 3rd, but wondering if anyone else went through this? I have a flex disk/giubo on order just in case.

[oceansize]

Seems like when I replaced mine you needed to move the CSB forward (towards engine bay) 10mm to 15mm or so before tightening down. If you didn't do this, then perhaps...?

[heinzboehmer]

Did you torque the bolt that holds the two halves of the driveshaft together? Recently had mine back out and it sounded exactly like a bad CSB.

https://nam3forum.com/forums/forum/main-forum/member-build-journals/13854-heinzboehmer-s-2002-topaz-6mt-coupe?p=278591#post278591

[siamkazi]

oceansize and heinzboehmer , these are absolutely spot on suggestions, I'm going to find out this week once we get under the car again to inspect!

Much appreciated! I'll update our findings here for others who may come across this.

[sapote]

just changed out the CSB and now there's a rumble/vibration from 2.5k to 4k in second gear,

So problem only happened after changing the CSB?

[siamkazi]

So problem only happened after changing the CSB?

Correct, CSB and exhaust hangers were changed, which most likely means: CSB needs to be adjusted or the driveshaft may be out of wack. From what I researched, could potentially be flex disc/giubo but it looked fine when we were underneath the car prior to changing the CSB.

[siamkazi]

Update: Ended up being the driveshaft itself, the middle joint had gone bad. We used a driveshaft from another M3 to confirm.

Prior to this: Giubo looked good under inspection, we added more grease where the pumpkin and driveshaft meet (checked the seal as well) but issue still persisted.

Runs smooth now. Thanks everyone for your help and input!

[sapote]

Update: Ended up being the driveshaft itself, the middle joint had gone bad. input!

Next to CSB?

[siamkazi]

Next to CSB?

Yes the center joint, i think it's called a U-Joint, probably got bent when the CSB went bad and the driveshaft started banging against the chassis

[sapote]

Yes the center joint, i think it's called a U-Joint, probably got bent when the CSB went bad and the driveshaft started banging against the chassis

Letting the driveshaft hanging on one end without proper support would cause damaged to U-joint. People ignored this when working on it and ended up with more headache.

[siamkazi]

Letting the driveshaft hanging on one end without proper support would cause damaged to U-joint. People ignored this when working on it and ended up with more headache.

That's a great point, hopefully this thread helps others in the future, it was definitely frustrating to find the root cause.