Hi

I had the shop do my subframe mounts, diff mounts and 2 flex discs. The subframe was removed for this. I now have a noticeable vibration on takeoff and vibration at low speeds and a loud drone at higher speeds. All control arms are new too.

The vibration on takeoff points to the driveshaft. I searched for this problem and the solutions are varied - centre bolt too tight, flex disc bad/reversed, centre bearing and support (this was not replaced). In putting everything together could the diff alightment be off? Centre bearing go bad? Everything was very quiet before the "big operation". Any suggestions on how to pursue this?

Thanks and Regards
Oreo
124 200E

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1992 124 E200 (Euro)

Was the driveshaft seperated at the center spline without the two halves being matchmarked first and then put back out-of-balance? Look for matchmarks, painted dots etc.

Is everything tightened properly? Flex disc, Center support bearing, axle half shafts to differential, subframe mounts.

Does the tech remember removing and re-installing a shim on the top forward bolt of the differential (between the body and the differential housing)? This changes the pinon angle.

Were the diff. mounts indexed (clock position) properly? Compare to another 124.

Is the exhaust hitting the body anywhere?

Hi Bear

Very good point - I was thinking about this too. Will the shim for the diff front mount change things drastically? I remember this shim as I changed the front mount myself. I got stuck at the rear when the 12mm bolt stripped and had to have a "head" weld on to remove - hence I had to have the shop complete the job. They might have moved the shim up thinking it was a washer.

Oreo

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1992 124 E200 (Euro)

Most driveshaft vibration is caused by the center support. The bearing usually doesn't go bad but the rubber portion that holds it does. When that rubber gets weak it allows the diveshaft to deflect from the "true path". You feel this as a vibration on takeoff as it takes the torque of the engine pulling on the car to deflect the support.

Believe that the transmount, or is it the center support should be left a little loose. Car driven slowly forward and back a couple of times to allow everything to settle in place. Then the do the final tightening.

Steve

Guys

Update: I checked the postion of the shim for the forward diff mounting and indeed it was wrongly installed and used as washer for the nut. I repostioned it and the takeoff vibration was reduced significantly. However, the the driveline still makes a droning sound from 50mph onwards but only under accelerating pressure. Everything is quiet on coast down.

I also had the shop replace the centre bearing and carrier but it did not change anything but did give peace of mind for the future. I inspected everything that was done and it seems that there's nothing I would do differently. Diff oil was also replaced to take that out of the equation. The mech says that it may be the diff gears but I doubt that as the box was silent before. At speed, the sound is a kind of low drone like a vibration but I can't feel it in the cabin.

I'm wondering about the alignment procedure regarding fitting of the vibration damper next to the front flex disc. Is there only one way to fit this on the shaft? And, as the name implies, would this be critical to reducing/causing vibration.

Also, since the little 1 mm shim cured the take off vibration, it seems that the diff is very sensitive to alignment. Is there a known procedure to align this on a pitch and yaw angle? It seems slipping washers between 2 of the 3 bush joints would do the job but the theory is beyond me.

Thanks and Regards
Oreo

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1992 124 E200 (Euro)

Pretty sure Alldata has the info on this, I don't have access to it currently but even when it was shown to me it was very complicated and I didn't fully comprehend it.

Yes it is a sensitive angle to position, after coming to the realization (took about a year ) that I just didn't have the time to do the bushings my indy did them. Pick the car up and it is smooth as glass, go back to tell him and he said the spacer looked too thin so he put a thicker one in that he had on the bench.

Moral of the story, stick a 50% thicker shim in there and give it a try!

Were your diff. bushings indexed properly?

Were your tires rotated during all of this to cause a noise?

Hi Bear

The car was silent before all of this so tires and diff I would rule out. I am coming to the realisation that it might be the U-joint on the driveshaft. Now that the new bushings are in (it is indexed correctly), it might have changed the angle of the shaft and working it across some worn in areas. I came across some posts on this.

There was some advice to put some washers at the support bearing to try and move it to a different position. I will be trying an additional washer to space it more and see if it changes anything but that U-joint is becoming a big possibility.

Regards
Oreo

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1992 124 E200 (Euro)

Hi All

Just wanted to update that I have found the problem. I have to eat my words that I wont't do anything different from the mech. It turns out that when they replaced the front flex disk they didn't match up the holes for the vibration damper and the prop shaft flange. So they missed the shaft altogether. The vibration damper was holding everything together! This was visible only when the transmission support bracket was take out.

I realigned the holes and everything is back to Mercedes smoothness. More so with all the new rubbers. I haven't had a word with the mech yet. How would you put it to him?

Oreo

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1992 124 E200 (Euro)

Just " Put it to him ".

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2007 C 230 Sport.