Odd Vibration

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Bennett

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My car is experiencing an annoying small vibration that appears to be coming from the differential. I have a 5 speed conversion. The diff mount has been welded for additional support. The driveshaft was recently balanced and rebuilt with a new center support installed upon re-installation.

This occurs only at low speed / low RPM (35 mph / 2500 rpm) when shifting from first to second.

Thoughts?
 
Check the tranny mount

I had the same vibration at that speed with the automatic I used to have in the car- just a thought, otherwise you just have to start from one end and go all the way through. There may be others on the forum with more concise answers-

Good luck!
 
did it start right after the drive shaft work? if so perhaps check there again, did they "pre load" the center bearing per the manual when reinstalling?
 
Also check to see if they put the drive shaft halves back together as they were before - if not this could cause imbalance. They should have marked them prior to separating.

Bennett said:
I will inquire re the pre-load. It did start after the work as done.
Click to expand...
 
Mmm... 35 mph in first is reving way past 2500...?

35mph is past 5500-6000 in first gear and not recommended for very long without breakage.:twisted:

Try this... when it starts put your hand on the tunnel and feel if the vibration is front or rear... move your hand.

Get under the car and shake the bejusus out of the driveshaft and see it there's something loose. Check the guibo ( the rubber donut on the end of the trans) for cracks. Don't forget the little rubbers on the exhaust mount that attaches to the trans. Over rev?

What Steve means is this; the bearing between the two shafts should be pushed forward a 1/4" to preload the bearing/ rubber/ mount. If it looks a bit distorted or leaning towards the rear then loosen the two nuts, push it a bit forward and retighten.

Backlash in the diff- slop. It should be little to none.

And lastly, this isn't for everyone- jack up the car, secure it, run it in low and see if you can see the problem....After reading the first part of the sentence- safety. Careful.

After all that- driveshaft alighnment- a piece of string, streached, to make sure the shaft isn't ****ed off to the side, etc. And if that doesn't do it, reclock the driveshaft- unbolt one end, rotate 90 degrees and retighten.
 
Did you drill the driveshaft or cut the output shaft?
Is the Guibo centered?
 
I will be taking these suggestions to the mechanic as he revisits the issue. As for RPMs - the situation occurs when shifting to 2nd from 1st and once in 2nd gear the vibration occurs while RPM's climb from 2500-3000 and speed is around 35-40 mph. - unless my speedo is way off.
 
Stevehose said:
Also check to see if they put the drive shaft halves back together as they were before - if not this could cause imbalance. They should have marked them prior to separating.
Click to expand...

Convinced that this is the issue. Had same problem years ago. Disassembled the two halves, rotated one section and put it back together. Perfect ever since. You may have to do it a couple of times, trial & error.
 
Hi,

I still have the same probleem. It's vibration a 40 to 50 km in second gear. I changed the drive shaft which I borrowed of a friend. He was also driving his e9 with a 5 speed. This didn't solve the probleem.

I rebalanced my own drive shaft, , changed the pre-load, changed the middle hanger, but no result.

My set-up is: 2800cs with an 3,5m30 engine with a getrag 265 (od). I need to change the seal on the rear of the gearbox because it's leaking, so I have to brake down some things. I would be nice if one of you has some suggestions that I can try at the same time to solve this vibration problem.
 
There were three driveshafts. At least there were two center bearings; one being smaller and not so known any longer; early automatic IIRC. I know W&N has the part. So you might want to measure yours. Regardless, it should be a light press fit with no play.

I suggest you start checking and determining driveline alignment with an eye for metal wear which should be showing somewhere not readily visible. Centerlines as well as angles. It possible with swaps or age of things such as brackets, mounts, etc. Something is causing the vibration. If you're positive of the driveshaft, look elsewhere.
 
Hi

Thanks.

I use a new center bearing of W&N and also tried the original from BMW, no difference.


I did check (and re-check) the drive shaft for many times (and hours). To get the drive-shaft in exact position I need to higher the back-end of the gearbox. That's not possible because it hits the tunnel. Sure, I can solve that by lifting the tunnel by a few cm. Before I do that, I want to be sure I've tried about everyhing else that you can advise me.

Could it be that the bearing on the rear of the gearbox is bad and give the vibration?
 
Try this:

http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdf

Since your dealing with a swap, measure the rear diff pinion angle and compare it to the trans after you check the rear mount. It could be you just need to shim things a bit. My guess is at the trans.

IIRC, there is a posting on making up your own wooden jig to do just this procedure. While this takes care of angle, there is still side to side or lateral alignment to consider.

The other thing is to have a friend drive and using your hand on the floor try to determine exactly where the vibration is coming from either back or front. Not exactly rocket science but has worked for me before.
 
Mich said:
I did check (and re-check) the drive shaft for many times (and hours). To get the drive-shaft in exact position I need to higher the back-end of the gearbox. That's not possible because it hits the tunnel. Sure, I can solve that by lifting the tunnel by a few cm. Before I do that, I want to be sure I've tried about everyhing else that you can advise me.

Could it be that the bearing on the rear of the gearbox is bad and give the vibration?
Click to expand...

Bad transmission bearings are generally noisy with an accompanying rumbling and/or roughness that could be likened to riding on a rough road bed. Worn trans bearings might also be indicated by metal particulates in the trans lube and/or excessive metal filings stuck to the magnetic drain plug. The noise/vibration would most likely be felt in all gears or when the clutch is disengaged and there is a load on the transmission. This is not what I think you are describing, which is more akin to shaking a paint can.

I am probably repeating what others have suggested. That is physically getting under the vehicle to look for and possibly see the offending vibration. This entails securely lifting the vehicle and replicating the engine speed and gear selection that brings on the most vibration. This generally makes pinpointing the cause or suspected cause much easier than feeling for the general location of problem.

Drive shaft un/balance has been discussed on this forum. Second gear vibration was mentioned but do not believe there was an ultimate resolution posted. http://www.e9coupe.com/forum/showthread.php?t=10322

If your drive shaft rebuild was done properly, chances are good that it was balanced as a single unit. That leaves the installation, including mounting and hardware as possible culprits. Setting aside the proper alignment which 61P has outlined, is it possible that you have some mismatched hardware, such as some fasteners that are longer or shorter than others? (I recall removing half shafts from an e24 and being surprised by two or three different styles and fastener lengths. Unknown whether it caused vibrations, but I doubt it would have contributed to the balance.)

As mentioned in the referenced post^, another wild idea concerns the grease and center alignment hardware for the front end of the drive shaft. I would not generally expect this aspect of the drive shaft maintenance and design to cause your problem, but it might have something to do with it. Typically the nose of the transmission output shaft fits inside a small cavity at the front of the drive shaft. The shop manual recommends greasing this area. How critical this is on the standard 4-speed setup is unclear. However, the need to properly align and grease things may be more pronounced since you have modified things, and by your own admission, the drive line alignment is possibly pushed beyond its reasonable limits. Parenthetically, I recall reading somewhere that the joints can be damaged if they deflect more than 16-18 degrees.

11501001_z.jpg


Best of luck.
 
Thnx for the reply. The center alighment is oke, I've checked that several times. Grease on the center parts, I can check again. Don't know about that.

Another question: Did anybody of you had to lift up the tunnel to get a 265 getrag in the right place?
 
One thing I have not heard is the possibility of a bad engine mount, hard to see and they will break from age.
Sometimes we do not see the forest for the trees and start on the wrong path. Seems you have addressed all the other possible defects.
 
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