Bad vibes with recon'd driveshaft?

[beetos]

Hi all,
I recently pulled my driveshaft to fit a new centre bearing assembly which had completely collapsed causing knocking in first / second. While at it I installed the short shift kit from BMA and stiffened up the rear shifter carrier mount using 'shadetree mechanic' techniques. The shift is now a superb; short and precise.

Upon pulling the driveshaft I noticed the UJ was stiff and decided to have a driveshaft speciallist machine it out and put in a serviceable joint from a Holden. They also fully balanced the assembled joint.

I have a problem now that at about 10-25 mph there is a shudder/driveline drumming that is worst in first and second when you step on it. It was not there before so all I can assume is that the driveshaft was not quite balanced right. One thing that I half assed when installing was the rear CV joint connection. The funny shaped gasket that holds the CV grease in was torn so I used sealant on the faces of the flange. I am thinking that this is causing a slight run out of the CV joint (maybe).

Other than that I don't know. If the diff carrier bushes were gone it would have vibrated before. It was smooth as before apart from the knocking caused by the centre bearing mount.

I guess I should have just got a second hand shaft instead of trying to recondition/balance the old one. My back can't take another weekend on abuse!

[genphreak]

Hi all,
I recently pulled my driveshaft to fit a new centre bearing assembly which had completely collapsed causing knocking in first / second.... Upon pulling the driveshaft I noticed the UJ was stiff and decided to have a driveshaft speciallist machine it out and put in a serviceable joint from a Holden. They also fully balanced the assembled joint.I have a problem now that at about 10-25 mph there is a shudder/driveline drumming that is worst in first and second when you step on it. It was not there before so all I can assume is that the driveshaft was not quite balanced right....I guess I should have just got a second hand shaft instead of trying to recondition/balance the old one. My back can't take another weekend on abuse!

I'd take it down and let the dude that fux0red it feel the shudder. They might offer to help you pull it out, (have they got a lift?) and then you could rest more easily after the job or at least with less pain. It is probably a genuine mistake- give em the chance to fix it and all will be well. You want their skin in the game on the repair- or else once it comes back should it still be bad you'll be blaming the car again, and doing it thrice. Nick

[winfred]

the sealent shouldn't effect the ballence as most of it will squish out and the surfaces should align unless theres a big chunk of gasket on one side, i've had little luck with local driveshaft shop rebuilds on bmw shafts, i think the main problem is they have a hard time centering the joint in the yoke, you think they'd catch that during ballancing

[Hypr5]

UGH. Really?

I JUST installed my rebuilt yesterday. Same exact thing you had done, except with a Nissan U-joint. Machined, balanced, painted, etc etc - upon installation, the shaking / shuddering is worse than it was!!! It used to only do it upon acceleration at the top of each gear - now it does it while cruising at 25 - 35mph too! VERY frustrating - the exhaust is a tough job on jackstands when you have limited help. <sigh>

Keep me updated, I'll also let you know how it goes when I drop off mine to get the issue fixed. I was told that they had a hard time balancing, but now it's "good". riiiight.

~Don

[Hypr5]

The other thing I Just remembered...

will old trans mounts make a new driveshaft vibrate / shake?
In my experience, the tightness of the center bearing, etc will keep it from vibrating immediately, but the changed angle will shorten the life of the center bearing. I am wondering, because I would hate to remove, return, etc the driveshaft only to find nothing wrong with it and worn trans. mounts.

I do have experience with worn transmounts, new center bearing, etc, etc - but I dont think that they could be THAT bad, could they? It shakes upon deceleration, acceleration, steady cruising, etc, etc. It will only not shake at high RPM or on the highway....

Any suggestions?

Thanks!

[Hypr5]

bump?

[Hypr5]

Well - all fixed.

To whoever needs this information in the future - The driveshaft shop found the cause to be a "petrified guibo" Although it was brand new, it was the least bit flexible and caused a very violent shake.

[beetos]

Hypr5, glad you got it sorted. I left my guibo alone as it looked brand new. Now I am thinking that maybe its f'kd as mine is directly related to torque (ie worst in first when flogging it though to 40kph ish). Maybe I should have changed my wretched guibo.....oh my poor back is gonna love this

[beetos]

Guys, I thought I would bump this and ask another question. Is it possible that my craped out centre bearing mount was masking a faulty guibo, and now its changed out, the guibo is showing symtoms. I guess that whats Hypr5 is saying as if his guibo.

[genphreak]

Guys, I thought I would bump this and ask another question. Is it possible that my craped out centre bearing mount was masking a faulty guibo, and now its changed out, the guibo is showing symtoms. I guess that whats Hypr5 is saying as if his guibo.

I doubt it, it'd have to create the exact opposite harmonic, cancelling out like waves in water... I suspect you will find the shop didn't balance it very well... no one likes 2 piece shafts, is their machine made for a 1 piece perhaps? What have the shop said? I hope you don't have to buy another guibo just to conclusively prove its not that- another run on the balancer would have to prove it more easily...