NEED HELP! m50 swapped vibration

[sofa KING euro]

Hey r3v,
I recently purchased a late model e30 with an m50 swap performed that was not running. I got it up an running and have been driving it around as a DD ever since and now I've run into some problems. I wanted a more stanced out look so I temporarily purchased lowering springs offer a r3v member (bav auto springs to be exact) until I could afford some fully adjustable coilovers. It seems ever since that I have had a HORRIFIC vibration from 35 and up to oil speeds including 120. I checked the drive shaft out at work, I'm a mechanic, and found vulcanized rubber in the carrier bearing to be torn so first thought was this was the issue. I replaced it with one from bma and as soon as I got on the highway it was even worse. I checked me geibo it was brand new with the car and seems to be fine (no tears) and ive pryed on the u-joints to see if there was any play and nothing so my only thoughts are this... unbalanced drive shaft (unlikely because nothing appears damaged on the shaft and when I first started driving it there wasn't a vibration, a frozen trunnion on one of the u-joints (still seems unlikely), an incorrect driveline angle due to the swap, or an extremely incorrect pinnion angle from the lowering kit. I'm leaning towards the pinnion angle however I'm wondering if anyone else has experienced a similar issue after lowering there e30 with springs and how I can shim the diff to correct it. Any and all help is appreciated!!!

[sofa KING euro]

I guess it is also necessary to say I have an m50b25tu swap with the factory g260 tranny and e30 driveshaft and diff however the guy that did the swap had made a custom tranny bracket (don't know if the problem may lye in the bracket?

[nrubenstein]

Driveshaft vibration tends to decrease at speed. I would suspect something wheel related before driveline if it is vibrating like hell at 120.

[sofa KING euro]

tires were just balanced 2 days ago along with alignment and you can feel it in the floor board so I know its a driveline vibrations

[bubbajan21]

I know its a driveline vibrations

Is there a question in this thread if you already know what it is?

[sofa KING euro]

Yes i know its a driveline vibration but what is causing it. I guess what i am wondering if anyone has lowered their car with springs and experienced a driveline vibration from the pinion angle being off?

[nrubenstein]

Yes i know its a driveline vibration but what is causing it. I guess what i am wondering if anyone has lowered their car with springs and experienced a driveline vibration from the pinion angle being off?

Springs can't change the pinion angle, so we know that isn't the cause. Why do you think that they would? Neither the engine, transmission, nor diff is supported by the springs. The E30 is not a live axle vehicle.

The only driveline component that could be impacted by a change in geometry is the half shafts, although I don't know why they would vibrate like that from a small change in geometry.

[OTT]

The carrier bearing could cause vibration if it's out of alignment. I don't know why you'd only notice it now that you put springs on but it's worth checking out.

Are you sure you only changed the springs? Did something happen that could cause your drivetrain to move? Did you replace your torn carrier bearing?

[scottinAZ]

the key here is the torn carrier bearing. Sure fire sign of the u-joints turning to shit. Replace/reman the driveshaft, and be done with it.

[sofa KING euro]

^thanks scottinAZ I appreciate the help this is what I'm going to do...do you know anywhere I can purchase two quality u-joints online?

@nrubenstein not looking for an argument but how would changing ride height not affect pinion angle? IRS or not ride height will directly affect pinion angle and if it is too severe a shimmy may occur...this diagram displays it perfectly
http://www.google.com/imgres?imgurl=...QEwAA&dur=2380

[nrubenstein]

^thanks scottinAZ I appreciate the help this is what I'm going to do...do you know anywhere I can purchase two quality u-joints online?

@nrubenstein not looking for an argument but how would changing ride height not affect pinion angle? IRS or not ride height will directly affect pinion angle and if it is too severe a shimmy may occur...this diagram displays it perfectly
http://www.google.com/imgres?imgurl=...QEwAA&dur=2380

Uh, have you looked at how the diff is attached to the chassis? Please explain to me why you think that the diff, which is bolted directly to the chassis and the subframe would move when you change ride height. The CV half shafts change angles when you change ride height. The driveshaft angle is not altered. Ever. Unless you change the subframe and diff mount attachment points.

Throw the car back on a lift look at it again. If you still can't see it, compress the suspension and see what happens. As with any other IRS car, the diff will not move.

So, you may have a bad driveshaft, but that has nothing to do with the springs. It's remotely possible that you have a ride height induced vibration in the half shafts (although I would consider that unlikely). But any way you cut it, ride height has no impact on the the main drive shaft.