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Hello all,

Longtime lurker here. I've spent the past 3 months trying to fix this problem, but I can't seem to figure it out. I have a 2002 330ci convertible, 247k miles, with a ZF 5HP19 automatic transmission (A5S 325Z). After driving for a bit, if I apply more than half throttle, there is a noticeable vibration coming from the transmission/driveshaft area. Here's a summary of what I know and what I've done:

What I know:
  • Only happens after ~15 mins of driving, when car is warm. (Probably not related to engine temp, since engine reaches normal temp within 5 mins.)
  • Vibrations happens ONLY at 23-27mph, under load, like high throttle or going uphill. Happens regardless of gear (I used steptronic to test in gears 1-2-3). Above 28mph is fine, it cruises beautifully at 70mph.
  • Vibration stops when I let off the throttle
    • Vibration also stops when I press brakes while keeping throttle on (although this may be due to "brake override", which turns off throttle when brakes are on)
  • Appears to be coming from transmission or front driveshaft area
  • Steering wheel does not vibrate
  • No codes thrown by engine or transmission
  • Sport mode does not make a difference
  • Before replacement, guibo and CSB were in poor shape, but not ripped. One engine mount had completely separated into two pieces. Tranny mounts also shot.
  • Recently replaced, in an attempt to fix problem:
    • Guibo
    • CSB (center support bearing for driveshaft)
    • Transmission mounts
    • Engine mounts
    • Transmission filter, gasket, fluid
    • Differential fluid
  • Unlikely:
    • Transmission fluid seems ok, magnets had reasonable amount of sludge
    • Transmission shifts fine
    • Differential fluid looked pretty clean, no metal particles
    • Driveshaft CV joint looked clean, no noises or play when turning driveshaft. Injecting grease into the joint didn't make a difference.
I have considered the following remaining possibilities:
  • Bad driveshaft U joints? (Could not hear characteristic tingling noise)
  • Bad diff, causing driveshaft to wobble? (Changed diff fluid, but old fluid looked pretty clean)
  • Diff bushings? (don't see how its related)
  • Driveshaft centering sleeve?
  • Rear axle CV joints? both have grease on outside.
I'll try to take a video sometime soon. What baffles me is that this happens only at a very low specific speed.

Please help! Does anyone know what could be causing the issue? What other tests can I do?
 

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Replacing my driveshaft eliminated very similar problems. I had also gone through all the other steps you tried first. It takes the most minute amount of play in the U-joint to generate vibrations and clunks. The U-joint could also wear out because of a failing Diff input bearing not keeping the flange centered or because of those failed mounts that you mentioned throwing things out of alignment. Before replacing anything else, you could try loosening every mounting point from the diff up to the engine, and just letting everything settle--a BMW indie tech told me that sometimes works for him.
 

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Have you checked your shocks ? My car was vibrating at high throttle at low speeds until I got around 40 and my rear shocks were blown, I replaced and problem gone
 

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I have exactly the same symptoms you have. It started about a year ago, so I replaced everything that you have with no change. Prior to replacing the parts, I assumed it would be the CSB, but when I removed it, all seemed OK. Since then I've had the driveshaft off more times than I can think of (maybe 10) trying to find the source of the problem.

Something that I read online somewhere that I did try is to make the CSB rubber surround more solid using polyurethane rubber. I tried a bunch of different applications, from filling the entire void on both sides to varying amounts of fill down to next to nothing. The more you put in, the more solid it is. This immediately removes the low freq vibration that you feel as you accelerate through about 25mph, but what it does do is introduce a buzzing vibration at higher speeds. The more solid you make the CSB, the more buzzing you get. I have however been able to get it to completely remove all vibrations.

If you look at the CSB, the surround cross section is like an S shape, with the cavity you can fill being the U that you seen on each side. Looking from the rear, the U is at the outside, and when looking from the front, the U is on the inside closest to the bearing. After much experimentation, I've found that if I fill the outside U only this works perfectly. It's never been smoother.

The nice thing about doing this is you don't have to remove the driveshaft. Simply remove the rear brace, exhaust and heat shields and you have access to where you need to fill up with the polyurethane.

In the middle of all this experimentation, I've had a number of conversations with a driveshaft specialist who has been dealing with BMWs for many years. It is his opinion that this is most likely the universal joint. Like Benny's comments above, he said the universal joint will feel fine, but the smallest amount of wear (which you can't detect) will cause the symptoms. The only option is to replace the U joint. Unfortunately, the U joint isn't a type that where you simply bolt on a new one. He said that you can either replace the driveshaft, or he could cut off the old U joint, and weld a new one on for about a third of the cost. Apparently this is a pretty standard procedure, with the advantage that if it happens again, the U joint is now a type that can easily be replaced if it fails again. My car is as smooth as butter at the moment, but I do plan to have the U joint replaced, as the wear is obviously there, and I expect that it's only going to get worse in the future.
 

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I'll see if I can dig up a photo.

With your CV joints, what's leaking there is just a tiny portion of what's in the joint. A serious leak would have loads of grease sprayed out all over the chassis above the joint. My guess is that what you have there would make little difference. If it did, you would expect to have problems at more than just the one speed. From all the reading and research I've done on the subject (which has been extensive), vibrations that are speed specific, especially low speed under load, are nearly always U joint problems.
 

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Attached is a photo of the fix that worked for me. The picture is a csb (I have numerous) that I experiemented with. This one has silicone whilst the one that is in the car now has polyurethane rubber, which is much stiffer. It shows where to put it though. As you can see, it is pretty easy to squeeze the rubber into the groove, then use your finger to spread it nice and evenly around without having to pull out the driveshaft. There is nothing applied to the other side. I did have it on the other side as well, but it made the whole surround too stiff.

I'm interested to see how the grease injection goes.

 

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