Vibration under acceleration

[Marc850]

Hello,

In my persistant quest to dump as much money as possible on my 850i, I am now investigating on the vibration I get at speed.
This happens only when I accelerate and it is more noticeable at speeds above 60 mph: I get a noisy (rhythmic low pitch) vibration which tends to go away when I lift off the throttle.

I have removed the exhaust and the heatshield, revealing the driveshaft. But I just don't see anything plainly wrong with it. The center plastic thing looks a bit old but is not severely cracked or anything. I have searched the forum and seen that the non serviceable U-Joint is sometimes faulty, but once again visually it seems good. The plastic thing on the gearbox also looks very good.

So my question is the following: What should I look for, and how should I test it ?


Thanks to everyone who can help



PS: The wheels are properly balanced and the tires are brand new. Also the bushings have been replaced front to back

[Goodguyili]

Have you checked the guibo? Look for any cracks or fraying of the material

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[rjjablo]

Grab the Driveshaft and give it a shake, its very obvious if you have a bad U-Joint, Once there you can also spin the driveshaft and try to move it from all angles.

Center Bearing is harder to test as it sits in a rubber cushion, at a Minimun inspect it for cracks and tears. I was going thru this on my POS Dodge Truck and U-Joint were bad and after I replaced them similar to what you describe and had to go back in and do the center bearing.

[Marc850]

The guibo was what I was referring as "the plastic thing near the gearbox". Here's a picture of it, it looks good, probably has been changed before.

IMG_7149.jpg

At least under the car it looked good, but on the photo we can see a slight crack in the middle. Do you think it's worth swapping it for a new one ?

Here's a picture of the center bearing holder

IMG_7155.jpg

Also looks and feels fine

Now for the U-Joint

IMG_7159.jpg IMG_7165.jpg

There seems to be a bit of grease and a dead ish joint. But I am not familiar with those. What I can say is that there is a bit of a greasy noise. Here's a video of it, I don't know if it sounds broken, or if it could cause my problem because i don't feel any noticeable play in the drive shaft.

[Timm]

Vibration above 40 MPH or so that is only present under acceleration is usually engine related (I know it sounds unlikely but bear with me)! The driveshaft and half shafts tend to centre themselves up at speed and any wear is more prevalent at low speed and high torque.

To see if this is the case, get to a speed where accelerating causes vibration and change down a gear and see if the vibration changes or disappears - a sure sign that you have a cylinder that is producing no power! I went through this on my V8 and it turned out to be a coil-driver had failed and I was running on 7 cylinders. The loss of a cylinder just wasn't noticeable at lower speeds.

[petejk]

My guibo looked good until I pulled it off the car, and found that it was a horror show cracked in multiple spaces.

My transmission mount looked good, until I pulled it off the car, and compared its height to a new mount. There was almost a one inch difference.


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[Marc850]

Well, I do have a kaputt oil scrapper ring on my sixth cylinder, flooding it and the spark plug with oil.

The vibration is really present on load, and it does change when I change the gear and completely goes away when I lift off the throttle.

[Goodguyili]

Well, I do have a kaputt oil scrapper ring on my sixth cylinder, flooding it and the spark plug with oil.

The vibration is really present on load, and it does change when I change the gear and completely goes away when I lift off the throttle.

Can bad transmission mounts create 60mph+ vibrations? Im pretty sure my are worn out and I'm dealing with this same issue

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[petejk]

Can bad transmission mounts create 60mph+ vibrations? Im pretty sure my are worn out and I'm dealing with this same issue

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It definitely wouldn’t hurt to change them. For auto cars they are inexpensive, and not too much of a hassle to change. You would probably want to change motor mounts at the same time


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[Timm]

https://www.meeknet.co.uk/e31/E31_Tr...eplacement.htm

[Marc850]

My gearbox mount is in a bad shape, it looks a bit squished by the gearbox weight. These are pricey on a manual gearbox tho...
Could they cause the noise and vibration ? Like maybe deviating the gearbox from it's correct axis ? I have had this for a while, hope it did not mess up the gearbox

[petejk]

I don’t have good news for you regarding the gearbox mount. If it’s original, it probably needs replacing, at the same time as the engine mounts. The part isn’t cheap, but isn’t going to get any cheaper, and there’s always the risk that it becomes NLA, like some of the other v12 manual parts.

Examples of this are the shift arm rear mount for the early cars, and the gearbox selector shaft seal.

Also, if you’re replacing the mounts, and potentially removing and inspecting/replacing the guibo, a good “while you’re there” would be to replace the shift bushings.


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[Marc850]

Yeah I will definitely be replacing it, here is a picture:

IMG_7174-1.jpg IMG_7175.jpg

The engine mounts looks good, they might have been replace at some point. Well, except for the fact that I have a new leak on the left side of the engine...

IMG_7176.jpgIMG_7177-1.jpg

[rjjablo]

Repeat after me, every rubber piece on this car is suspect and potentially rotten

[petejk]

This was the state of mine



I can’t seem to find the side-by-side new vs old transmission mount picture I remember taking, but it was equally as bad.


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[Marc850]

Ok, and did you feel the change after swapping it for a new one ?
The parts are already ordered, but can you tell me a bit more about the shift bushings ? I don't see what those are

Thanks

[petejk]

Ok, and did you feel the change after swapping it for a new one ?
The parts are already ordered, but can you tell me a bit more about the shift bushings ? I don't see what those are

Thanks

My car has been off the road in my garage while I’ve been taking it apart and putting it back together again, so I can’t tell you yet!

As far as the shift bushings go, they are all still available, with the exception of the rear shift arm bushing, for which there is a substitute - what year is your car?

Bushings listed here https://www.realoem.com/bmw/enUS/sho...diagId=25_0004

Turner may still offer a kit, which will include most of what you need


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[Marc850]

Hopefully it will have !

But you access it from the central console don't you ? The kit from turner is sadly NLA

One more question tho. Do I also have to change the guide bush when I'll be changing the guibo ? Is that an easy thing to do or does it require hydraulic tools ?

[petejk]

I would change the guide bush - it’s an inexpensive part, and if you’re changing the guibo, check the condition of your center support bearing.

Your best bet is to watch some of the videos out there for similar manual BMWs like perhaps the e34 or e39. That will give you an idea of what tools the jobs require. I know I spent a while doing that before ordering any parts.

As far as the shift bushings go, if you have the driveshaft removed, or at least out of the way, you’ll have all of the access you’ll need.


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[Marc850]

Hello,

A bit of a (late) update on this. I have replaced the centering sleeve, the guibo and the gearbox mount. I have had a specialist shop do the centering sleeve (which was loose), they also changed my U-Joint and balanced the driveshaft.
I then put it all back together and of course, it was worse than before. The initial vibration is still there and unrelated to the driveshaft IMO. But now I get a vibration + lower pitch noise from 70 KPH to 110 KPH. I took it all appart and had the guy balance it all over, put it all back and it's still there. I think I may even have a vibration when changing from 1st to second (30KPH I would say)

I now wonder if I might have messed up something: while waiting for the parts, the gearbox was supported on a jack stand with a piece of wood, but was sitting a bit lower than it's supposed to. Maybe I could have misaligned the thing ?

I took out the service manual, and there is a how to on centering and adjusting the propshaft which could be the answer to my problem. Has anyone ever tried this ? Can it be done without the special BMW tools ?

[Timm]

I bet he didn't pre-load it during installation as described here: http://www.meeknet.co.uk/e38/e38_remove_propshaft.pdf

[yacolt 8]

Hello to all fellow 8 owners
My issue is with motor mounts I have 95 840ci Garage Queen last Jan I replaced the motor mounts on both sides with the car having 98 thousand miles. Just today I noticed my driver's side mount is pulling apart. My question before I replace both of them what could be causing this? The car has been driven less than 3 thousand miles since the replacement was done. Presently OD has 101+thousand miles. All this is because I had a HOT start issue after getting gas my car would not crank over. After about 20 minutes car starts right up as all is fine. Going to get batteries tested to see if they are still putting out the AMPs needed to start the car then I will look into the starter and alternator. This may not go with this post BUT my question why are the motor mount falling apart. One thing leads to another. The car has been in my possession since 2003.

[Timm]

Not cranking when hot and then starts when cooled down a bit = starter motor!

Motor mounts - rotten non-OEM mounts or oil contamination

[Marc850]

Actually it was preloaded and installed by myself and I think i did it right. The gearbox looks to be centered after measuring.
Looks like I need to get my money back.

[TTTXGreg]

Do some searching and you will find there has never been (imo) a successful rebuild of these driveshafts. Buy a new complete assembly and I bet it fixes your problem. Join the club $!.

Hello,

A bit of a (late) update on this. I have replaced the centering sleeve, the guibo and the gearbox mount. I have had a specialist shop do the centering sleeve (which was loose), they also changed my U-Joint and balanced the driveshaft.
I then put it all back together and of course, it was worse than before. The initial vibration is still there and unrelated to the driveshaft IMO. But now I get a vibration + lower pitch noise from 70 KPH to 110 KPH. I took it all appart and had the guy balance it all over, put it all back and it's still there. I think I may even have a vibration when changing from 1st to second (30KPH I would say)

I now wonder if I might have messed up something: while waiting for the parts, the gearbox was supported on a jack stand with a piece of wood, but was sitting a bit lower than it's supposed to. Maybe I could have misaligned the thing ?

I took out the service manual, and there is a how to on centering and adjusting the propshaft which could be the answer to my problem. Has anyone ever tried this ? Can it be done without the special BMW tools ?