Vibration after transmission and driveshaft replacement

[janos_z]

I recently had my transmission (from Sun Valley) and driveshaft (from Driveline Service of Portland) replaced, and the car drives great from a power/responsiveness point. The annoying driveshaft squeaking is also gone. So that's all great.

However, now I have a new problem: on the highway, the car vibrates. It's coming from the middle of the car and can be felt by driver and passenger through the seats. I got my wheels re-balanced just to rule that out, and nothing changed.

I also noticed that when I rev the engine in park or neutral, there's a vibration 1000-1500rpm. Doesn't do it at idle, and doesn't do it over 1500rpm. I don't know if it was doing this before the recent drivetrain work - I never bothered to check. Is this a classic sign of anything?

Thanks as always!

 

[daantjie]

Could be drive shaft carrier bearing/mount and/or transmission mount, though I guess you would have replaced the transmission mount when you did the swap? Also how new are your engine mounts?

 

[JC220]

By driveshaft replacement do you mean the rear wheel drive shafts? Or the propshaft running in the centre of the car?

Things that usually are pooched by now are the centre propshaft centre bearing and bearing carrier. Check or renew both flex discs also if showing any signs of cracking or age at all. Germany SGF only. Check the propshaft has been assembled correctly if it had been removed. There are markings where the splines should go back to exactly. It could be that disturbing the transmission has ripped a worn centre propshaft carrier IMO worth checking first.

 

[Seangbadee]

Could be drive shaft carrier bearing/mount and/or transmission mount, though I guess you would have replaced the transmission mount when you did the swap? Also how new are your engine mounts?

Hopefully they aligned the ends of the propeller shaft correctly, and tightened the center bearing carrier to the chassis, with the car under load.

 

[leftyflyer]

As already stated above, check engine and transmission mounts. Obviously the driveshaft is not turning when you are in park and neutral.

 

[tz750twostroke]

I would suspect a torque convertor out of balance problem.

 

[JC220]

I would suspect a torque convertor out of balance problem.

I have never heard of such a thing, can you explain more? I am taking "Torque Converter" as being the transmission Torque Converter yes? Do you mean a bad rebuild on it?

 

[Jlaa]

@janosz

I recently had my transmission (from Sun Valley) and driveshaft (from Driveline Service of Portland) replaced, and the car drives great from a power/responsiveness point. The annoying driveshaft squeaking is also gone. So that's all great.

However, now I have a new problem: on the highway, the car vibrates. It's coming from the middle of the car and can be felt by driver and passenger through the seats. I got my wheels re-balanced just to rule that out, and nothing changed.

I also noticed that when I rev the engine in park or neutral, there's a vibration 1000-1500rpm. Doesn't do it at idle, and doesn't do it over 1500rpm. I don't know if it was doing this before the recent drivetrain work - I never bothered to check. Is this a classic sign of anything?

Thanks as always!

I recently had my transmission (from Sun Valley) and driveshaft (from Driveline Service of Portland) replaced, and the car drives great from a power/responsiveness point. The annoying driveshaft squeaking is also gone. So that's all great.

However, now I have a new problem: on the highway, the car vibrates. It's coming from the middle of the car and can be felt by driver and passenger through the seats. I got my wheels re-balanced just to rule that out, and nothing changed.

I also noticed that when I rev the engine in park or neutral, there's a vibration 1000-1500rpm. Doesn't do it at idle, and doesn't do it over 1500rpm. I don't know if it was doing this before the recent drivetrain work - I never bothered to check. Is this a classic sign of anything?

Thanks as always!

@janos_z - if you do a search, you may be able to find a thread from me about “vibrations heeby jeebies” that I posted last year with VOLUMINOUS information on troublshooting steps. Lots of info there and technical documents from MB about driveshaft angles and troubleshooting steps.

The most valuable tools I used to cure my vibes were (1) the NVH app which is an accelerometer app which allows you to characterize the vibration amplitude in various points in the cabins as well as frequency of the vibe which is critically important. You want to determine if the vibe is proportional to wheel rotation period or engine rotation period etc. and (2) process of elimination.

As you may know, the easiest thing to do from a driveline perspective is to play with shims at the trans mount and the rear diff mount. This changes the angle of the driveshaft. Of course don’t do any of this until you have fresh center driveshaft bearings and fresh trans mounts.

First things first - assuming all the parts above are fresh, at highway speeds, when you select Neutral gear, do you get the same vibrations as you do in gear?

 

[janos_z]

By driveshaft I mean the entire propshaft that runs from the transmission to the rear diff. I didn't do the work myself, but my mechanic said that it came pre-balanced and with new mounts. I believe the trans mounts are also new. I don't think the engine mounts are new.

@Jlaa, thanks, I did see your post and it gave ME the heeby-jeebies, because of how involved the process was - but it's a valuable resource, thanks for posting it, and I'll go back and take a deeper dive. I was hoping the fact that my car had recent work done would be some sort of magic clue to an obvious solution. Ha.

I did not test putting the car in neutral on the highway. I'll go do that and report back. Thank you!

 

[gerryvz]

It's going to be logical that (particularly if you didn't notice the vibration prior to the work done) the transmission and driveshaft work would be responsible for the vibration issue, everything else being equal.

Personally, to begin with, I would start with an assumption that the driveshaft itself is balanced, and was done properly by Driveline Service of Portland. That would leave the connections at each end of the driveshaft (the rubber guibos), the driveshaft center support bearing and housing, and the fitting of the two halves of the driveshaft together.

I think I would remove the driveshaft, and double-check that the two halves were put back together properly with the proper alignment. Were the flex-discs re-used, or new? If re-used, I'd consider replacing them with new units (the Febi re-boxed units should be OEM and good quality units). Also the center support bearing/housing -- was this factory part, or aftermarket? If you don't know, I would replace ALL of these parts with quality aftermarket or MB parts. But checking that driveshaft alignment would also be key.

Other than that, I'd also recommend, as was said, going back to Marc at Sun Valley and consider requesting a new/rebuilt torque converter to replace yours. I know that is a transmission drop (yet again), but if the driveshaft work doesn't solve the problem, that would be the next logical step. Obviously the transmission doesn't have to come out for the driveshaft work, so that's why I'd recommending checking/tackling that first.

Did you replace the rear crankshaft seal when you replaced the transmission? If you do end up pulling the transmission again, to check/replace the torque converter, I would STRONGLY recommend that you proactively replace that rear crank seal. It literally is incremental labor.

I would also check your motor mounts (it's documented here how to do this) as well as replacing your transmission mount, if you know it is not new. There is only a single transmission mount, and of course two engine mounts further forward.

 

[BlitzenBenz]

I had a vibration problem in my US 500E after replacing its transmission. I brought it the dealership (very close friend ran the service area) and he employed a factory tool that measured the alignment of everything from the engine to the diff. He identified a small misalignment, shimmed it, and it was perfect after that. I think it set me back 2 hours of labor, hardest part of the job was setting up the tool properly.

I learned from working with that same über tech that diagnostic efforts must Always be exhausted before even thinking about swapping parts. Pulling the trans because the torque converter Might be out of balance seems a bit much, especially if either recently refreshed or is original and did not cause a vibration before. I agree with the folks who've chimed in that you should first ensure everything is tight and fresh under there (perhaps most importantly the driveshaft center bearing). Be sure to verify your motor and trans mounts are not perished. If all looks good and nothing's loose under there, then before tearing into anything do yourself a favor and visit a dealership equipped to diagnose this sort of problem. FWIW this might be the first time I’ve suggested a “stealership” visit on a Board, but sometimes the folks that built and maintain the things are best equipped to provide answers. Good luck resolving your issue

 

[gsxr]

Do you know when (years/miles) the engine mounts were last replaced, and if OE/OEM mounts were installed?

Note that if the torque converter was unbalanced, this would cause a vibration that varies with ENGINE RPM, not vehicle speed.

If the vibration changes only with vehicle speed, not RPM, it's not the converter.

 

[janos_z]

Thanks, folks - this gives me several great leads. To answer some of the questions from above:

Putting the car into neutral on the highway did not change the vibration at all. I assume this rules out engine vibration as the cause - is that correct?

Gerry, your approach makes a lot of sense. I was told the center support is new, but came with the driveshaft and isn't OEM. IIRC the shop also said OEM center support is unavailable. A quick check online shows the bearing is available, so I'll have to ask them what they meant. And I'll have to check to see if the crankshaft seal was done; if not, I agree this would be the time to do it. BTW, are all Febi flex discs ok, or only some are reboxed? I ask because there's like a $100 difference between OEM and Febi and I want to make sure I don't accidentally buy junk.

Dave, the car has a tremble at 1500rpm with the car stopped, in park or neutral, but not as pronounced as what I feel around 60-70mph (and the engine isn't at 1500rpm at that speed). I'm hoping it's not the torque converter because I don't believe Marc's warranty covers all the labor associated with pulling and shipping the torque converter from here in San Francisco...

The car's going to the shop later this week. I'll post updates as I have them. Thanks again for all the great suggestions so far!

 

[BlitzenBenz]

Your driveshaft is still turning in neutral if you are moving (the differential insists). Check center bearing and drivetrain alignment. Good luck sorting this out

 

[gsxr]

Putting the car into neutral on the highway did not change the vibration at all. I assume this rules out engine vibration as the cause - is that correct?

Probably, yes.

Gerry, your approach makes a lot of sense. I was told the center support is new, but came with the driveshaft and isn't OEM. IIRC the shop also said OEM center support is unavailable. A quick check online shows the bearing is available, so I'll have to ask them what they meant.

The support is the rubber donut that the bearing presses into. The rubber support is NLA from MB. Not sure what the quality is like on aftermarket units. If your old one has the rubber intact, and is not sagging significantly, it may be serviceable. New ones sag almost immediately so there's not a ton to be gained here IMO. Update: The rubber support is available again from MB as of August 2022.

And I'll have to check to see if the crankshaft seal was done; if not, I agree this would be the time to do it. BTW, are all Febi flex discs ok, or only some are reboxed? I ask because there's like a $100 difference between OEM and Febi and I want to make sure I don't accidentally buy junk.

Febi flex discs were still OEM SGF made in Germany, last I knew. However, the Febi bolt kit will be Chinese. The OE bolts are stupid expensive. I'd be tempted to re-use the old hardware. Best case, you want the driveshaft balanced with both flex discs bolted to the shafts, so the entire driveshaft is balanced as a complete assembly. Dunno if this was done and/or if it can be done at your driveshaft shop.

Dave, the car has a tremble at 1500rpm with the car stopped, in park or neutral, but not as pronounced as what I feel around 60-70mph (and the engine isn't at 1500rpm at that speed). I'm hoping it's not the torque converter because I don't believe Marc's warranty covers all the labor associated with pulling and shipping the torque converter from here in San Francisco...

The car's going to the shop later this week. I'll post updates as I have them. Thanks again for all the great suggestions so far!

Check the engine mounts by measuring between oil pan & crossmember, search the forum for details / photos. If the mounts are collapsing/collapsed, this could cause multiple issues and also affect driveshaft alignment. OE only for the engine mounts btw, and they are spendy.

 

[janos_z]

Minor update: the car is at the shop and nothing obvious is jumping out at them. They said the (new) driveshaft has the weights on it from balancing, so they assume that's fine.

I looked back at my records and noticed that the transmission mount and motor mounts haven't been changed since 2010 (though only 50k miles ago). So maybe that's a good place to start, since they're probably due anyway and I wouldn't be surprised if all the jostling around from the recent major work did something. I am slightly concerned that fresh mounts might just mask the problem instead of fix it, but hey, if a tree falls in the woods...

Oh, and the crankshaft seal was done when the transmission came out. Phew!

Thanks again, and more to come.

 

[Jlaa]

@janos_z - good stuff! If, after having the motor mounts and trans replaced, you do not feel any difference, I would be happy to sit in your car while you drive and I operate the NVH accelerometer app to characterize the vibration. We are only a mile away from each other ….. but only if you want to!

 

[gsxr]

I'd measure the engine mounts first before replacing, just to see if they are marginal or not. It would be an interesting data point if you do replace the mounts and find a substantial improvement. Even better if our esteemed scientist, Dr. Jlaa, could apply his magic NVH tools for additional diagnostics.

 

[janos_z]

@janos_z - good stuff! If, after having the motor mounts and trans replaced, you do not feel any difference, I would be happy to sit in your car while you drive and I operate the NVH accelerometer app to characterize the vibration. We are only a mile away from each other ….. but only if you want to!

That would be awesome! Thanks so much!

I'd measure the engine mounts first before replacing, just to see if they are marginal or not. It would be an interesting data point if you do replace the mounts and find a substantial improvement. Even better if our esteemed scientist, Dr. Jlaa, could apply his magic NVH tools for additional diagnostics.

Great idea! I should have done the measurement before dropping the car off....

 

[janos_z]

Engine mounts were 23mm using the GSXR Method (TM), so I decided to leave them for now. Given that 1500rpm tremble, though, I've got my eyes on them.

As for the vibration at speed, my shop graciously swapped different wheels onto my car and took it for a spin, and they said they could no longer feel any shaking. I thought I had eliminated this possibility by getting my wheels balanced as the first step, but maybe not.

The timing is weird though. It wasn't doing this before all that driveline work. I guess I can get new tires (these are about 7 years old anyway) and keep my fingers crossed... In the meantime my power steering pump has started dripping onto the garage floor, so it's on to the next adventure.

I'll post an update after I get new tires, but that prob won't happen until a little later. I'm trying to pace myself...

(@Jlaa, I'm still up for a ride with your NVH app, if you're game)

 

[Jlaa]

Engine mounts were 23mm using the GSXR Method (TM), so I decided to leave them for now. Given that 1500rpm tremble, though, I've got my eyes on them.

As for the vibration at speed, my shop graciously swapped different wheels onto my car and took it for a spin, and they said they could no longer feel any shaking. I thought I had eliminated this possibility by getting my wheels balanced as the first step, but maybe not.

The timing is weird though. It wasn't doing this before all that driveline work. I guess I can get new tires (these are about 7 years old anyway) and keep my fingers crossed... In the meantime my power steering pump has started dripping onto the garage floor, so it's on to the next adventure.

I'll post an update after I get new tires, but that prob won't happen until a little later. I'm trying to pace myself...

(@Jlaa, I'm still up for a ride with your NVH app, if you're game)

Yes, Sat is good!

BTW regarding the wheels:

a) What were the roadforce balance numbers?
b) Did they clock the tires to the wheels based on the roadforce numbers? (dismount the tire, rotate the tire on the wheel, and remount, and then re-check the roadforce numbers?)

I just wrote the process up in a primer here: HOW-TO: Roadforce & Balance your wheel/tire assemblies to be free of vibrations: | "HOW-TO" Tutorial Articles

You want all four tire/wheel assemblies to road force at 15lbs or under for best results
Mine finally roadforced at LF 5 lbs, RF 9 lbs, LR = 8 lbs, RR = 9 lbs.

Roadforce is measure of how non-round the entire tire/wheel assembly is. The lower the number, the more perfectly round it is. Only after the tire/wheel gets under 15 lbs roadforce do you then move on to dynamic balancing .... there's not point to balance an assembly that isn't round to begin with.

 

[janos_z]

Thanks for that great write-up on roadforce balancing! I took the car to Rolling Stock for the balancing and I have no idea if they clocked the tires to the wheels. I do remember having the numbers in my hand, but apparently I didn't file them away in the car's binder. Maybe it's in the car still, which is at the shop. I'll post the numbers when I find them...

And cool, let's go for that NVH ride when the car's back in my possession!

 

[kegmankipp]

The support is the rubber donut that the bearing presses into. The rubber support is NLA from MB.

The center support is back in stock at MB. I picked one up from the dealer yesterday!