CSB Preload damage?

I had been hearing a worsening clatter from directly below my handbrake/center console area while under torque. Sure enough, the CSB bracket was cracked and the crack had run into the actual assembly a bit too.

After replacing it and the Guibo, the same issue except the sound was now higher pitched and different in tone, but similar symptoms. The same cadence, if you will, and mostly when under torque. For whatever reason it has never occurred in reverse gear. We scratched our heads a bit and decided I had bad U-Joints that were either responsible for the sound themselves (at least in part) and/or immediately damaging the new CSB and thus the repeat symptom.

Tonight my buddy said he had the answer, which is that we failed to preload the CSB and it had shredded itself. We simple centered the bolts in the slots and tightened them down, when we should have pushed it forward and then tightened. I would like some input before I order another one and go through the whole mess again. Do you think a failure to preload would cause immediate major damage to the CSB? What kind of damage would you expect? He felt that not preloading would shred the rubber, but the old CSB was cracked mainly in the bracket and a bit into the assembly itself.

Thanks a lot for the feedback.

Welcome to the fest!

Not preloading the bearing will result in just what you had happen. The previous one probably cracked because it was old and worn out. The crack was a result of the loose motion from wear, and that transferred to the mount.

Did you keep the front driveshaft in register with the rear when you replaced the CSB? They are balanced as a unit, and if you get it turned so that the two parts don't align the same as when they were made, you get vibration and premature CSB wear.

Thanks HH! Yes, the shafts were aligned via marks made on both sections. Thank you for your answer. I wasn't sure if failure to preload could immediately (and I mean immediately, as in the first block of driving) damage the CSB. Sounds like the answer is yes, and therefore I will order another one, this time preloading correctly. There seems to be some debate about exactly the correct procedure for E30 CSB preloading so comments along those lines are welcome as well.

It is not going to be fun to repeat this process

I think it doubtful that Failing to preload the CSB mount is not going to cause failure within the first few hundred metres of operation.
It sounds like the mount was a victim of poor quality control. or damaged while the bearing was being pressed on to the drive shaft.

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Whoa! Failed in the first BLOCK of driving? No way. There was something defective about the replacement or someone damaged it installing it. Even with no preload it should have lasted several hundred to a few thousand miles.

Sounds like I'm back to square one. Keep in mind, the symptom is very similar before AND after replacing the known-bad CSB. So by logic, if the same symptom immediately reoccurred, either the brand new CSB immediately failed OR the CSB is not the problem, or at least not the ROOT cause of the problem. The fact it immediately reoccurred is why we suspected the U-Joints being bad. I don't know much, but one thing I do know is that bad U-Joints can cause a CSB to fail very very quickly. It could also be that the U-Joints themselves are responsible for the sound under torque, and the broken CSB is just a symptom of the bad U-Joints.

I think the odds of a high quality replacement CSB immediately failing in the exact same way as the OEM CSB due to poor workmanship is pretty darn low. This was a Febi-Bilstien replacement, as near to OEM as you can get. I specifically sought out the highest quality components I could find, avoiding all-in-one kits that were half the price and purchasing each part from the best manufacturers. Anything is possible but...

As for incorrect installation, I don't know. We followed instructions to the letter but since those instructions (from Pelican) omitted the preload then we may have flubbed something. The procedure is fairly simple tho, I can't really think how we would have damaged it. It was inspected before and after attachment to the driveshaft and looked fine. Up until you bolt the bracket onto the car, it essentially just swings free on the shaft.

Err, missed this part, eh?

Hmmm.. I never pre loaded my center bearing... that was 15k miles ago atleast.

Maybe not always needed? ( or atleast I'll tell myself that)

Originally Posted by hornhospital

Err, missed this part, eh?

Yes...until it was too late

But it doesn't seem that failure to preload would insta-destroy the CSB.

Sounds like you need to get your shafts balanced. I had a s-10 with a 383 stroker in it with same issues. I had aluminum shafts made and balanced and took care of my terrible vibrations and noise.

I agree with Newman

you need to get your shafts balanced

.
Here in Africa I would take the whole shaft with Centre bearing et al to my friendly propshaft reconditioning shop & tell them to check, repair & balance
It is not expensive if they do not have to replace parts..
& it makes a sweet ride