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. :p 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...

[GS535i]

Is there not a certain preload that is recommended be placed on the center carrier bearing bracket before it is bolted down? I'd have to check Bentley to be sure - but this may have a bearing ( sorry for the unintentional pun ;) ) ....

[beetos]

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...

I suspect your right, i tried various pre-load on the centre bearing to no avail. Should have left it well alone to be honest.....:(

[angrypancake]

beetos, where you been? what happened with selling your car, i remember coming across it on fleabay a while back. i hope you didnt have to sell it.

[beetos]

g'day mate. Luckily I never got what I wanted and decided to keep it. We found 'other ways' of getting over my cash flow problem and got the house we wanted. Been busy moving in. Pleased to say the black beast is running like a champ! (with a bit of a vibration though....)

[Hypr5]

Well the pre-load won't really change vibration, just the life of the center support.

I just had a defective-from the factory flex disc. The thing just didn't flex. It was crazy. But if you didn't change yours, and it looks to be in good condition, that's not it.

Did the driveshaft shop check the driveshaft CV joint? It can cause similar symptoms. Either way, it's either a balance issue or improper/bad center support (most likely)

Hope you get it all worked out. I know that was frustrating. Had to drop the exhaust + dshaft 3 times in under a week.

[beetos]

So far, have changed out the guibo for a new one, put in new trans mounts, tok the shaft back to the shop and had it double checked. They reckon its spot on.

Its still drumming in first / second when taking off swiftly. Its fair to say that its a torque related problem in that you can coast through the driveshaft speeds it does it at and it wont vibrate. Its only when there is torque going thought it. Once above about 40kph its fine.

I think that the driveshaft is cursed. Should have left it alone I reckon. Can anyone describe symptoms of a bad CV joint at the end diff end and bad diff mounts?

Cheers

[beetos]

Another thing, I noticed tha shaft kicks off center from the centre bearing to the diff. The driveshaft shop said it had to be this way to make the UJ work properly. It that right?

[Jon K]

um if they had to kick it to the side, they used a driveshaft/u joint that is too long for teh car. Thats wrong.

[beetos]

The UJ used the same centres as the old yolk so I don't think thats the problem. My guess is that the driveshaft is set up to run as a two plane system (offset in vertical and horizontal planes). You will notice that the centre bearing carrier is offset to give horizontal plane offset. I am not a driveshaft guru but have read that the UJ need a certian angle to work right and 2 plane systems have to be have both angles within certian limits.

This knid of makes me wonder about the angles when my center bearing was collapsed and the shaft was running with a different angle than it is now with the bearing carrier holding it up in the centre of the housing. It never shuddered with the collapsed bearing mount, just knocked.

Can someone please verify if it at least looks right?

Thanks.

[beetos]

One last question on this please, can someone check that the offset on the centre bearing carrier is towards the right (drivers) or left (passenger) side? I can't remember offhand, and the pictures I have seen in bentley's and on bmwe34.net suggest mine is on wrong!

Thanks.

[mamilapon]

When you pulled the drive shaft out, did you tamper with the centering pin?

[beetos]

Not sure if I know where that is, but if you mean the centering pin on the trans output shaft, it was not disturbed.

Thanks.

[beetos]

All sorted. Your driveshaft should NOT look like mine in the picure above. The driveshaft shop put the center bearing carrier on the wrong way. I just got finished changing it back to how it should be (not bad, took 2 hours on my back) and it is now straight and runs smooth as!

[mamilapon]

Good on you mate,yet another experience to put in the book!!

[mamilapon]

Where's the picture?

[beetos]

Where's the picture?
Cheers mate, pics on page 2 of the thread.