5 speed back forth shuffle - PeachParts Mercedes-Benz Forum

Proctor750 · #1 02-05-2013, 05:04 PM

So I read other threads and posted another about this oscillation I get under acceleration if there is any slack in the drivetrain. I can't figure out If it is the backlash on the diff, maybe axles, or possibly (if its dual mass) the bushings that hold the two masses of the flywheel together??

There is a looseness somewhere in the drivetrain, the flex discs and center bearing are fine. Could backlash get this bad? Car does have ~400k.
If you lift off the throttle you get an oscillation, but if you try to get back into it without either easing into it or flooring it (so part throttle) this thing will start shaking back and forth harder and harder until it rips itself apart.
I have trained myself to drive around this issue, but would love to know what is causing it.

Also: the tabs on the rear seat, which direction to I push/pull them to remove it? towards the rear, or towards the front of the car?

whunter · #2 02-05-2013, 05:49 PM

Quote:

Originally Posted by Proctor750

So I read other threads and posted another about this oscillation I get under acceleration if there is any slack in the drivetrain. I can't figure out If it is the backlash on the diff, maybe axles, or possibly (if its dual mass) the bushings that hold the two masses of the flywheel together??

There is a looseness somewhere in the drivetrain, the flex discs and center bearing are fine. Could backlash get this bad? Car does have ~400k.
If you lift off the throttle you get an oscillation, but if you try to get back into it without either easing into it or flooring it (so part throttle) this thing will start shaking back and forth harder and harder until it rips itself apart.
I have trained myself to drive around this issue, but would love to know what is causing it.

Also: the tabs on the rear seat, which direction to I push/pull them to remove it? towards the rear, or towards the front of the car?

Call me to discuss the backlash.

.

vstech · #3 02-05-2013, 09:48 PM

Quote:

Originally Posted by Proctor750

So I read other threads and posted another about this oscillation I get under acceleration if there is any slack in the drivetrain. I can't figure out If it is the backlash on the diff, maybe axles, or possibly (if its dual mass) the bushings that hold the two masses of the flywheel together??

There is a looseness somewhere in the drivetrain, the flex discs and center bearing are fine. Could backlash get this bad? Car does have ~400k.
If you lift off the throttle you get an oscillation, but if you try to get back into it without either easing into it or flooring it (so part throttle) this thing will start shaking back and forth harder and harder until it rips itself apart.
I have trained myself to drive around this issue, but would love to know what is causing it.

Also: the tabs on the rear seat, which direction to I push/pull them to remove it? towards the rear, or towards the front of the car?

that sounds terrible... bring me your car, it's not worth messing with... I'll take it off your hands...

Proctor750 · #4 02-05-2013, 11:35 PM

lol Im going to sell it soon btw.... since it's SUCH a terrible car and all...

You know there is something about this car, I can't put my finger on it, that makes me want to find an excuse to go somewhere in it. It just wants to be ON at all times just putting away like a generator. And its suspension feels like rolling on clouds at 40+ mpg. It vibrates and keeps you calm, and never in a hurry. What a great little car. I will be sad to see it go.

Stevo · #5 02-06-2013, 10:19 AM

I wonder if it could be weak springs in the clutch disc? Do you know who long its been since the clutch was done?

Air&Road · #6 02-06-2013, 10:24 AM

Check the differential mounts.

raysorenson · #7 02-06-2013, 10:58 AM

Quote:

Originally Posted by whunter

Call me to discuss the backlash.

Anything to share with us? I'm in a death match with driveline slop on my '87. I will win eventually.

Some of this is in the rear diff mounts. I made some poly diff mounts that helped significantly with minimal increase in NVH.

Stiffer OM60x motor mounts?

Now I'm exploring fabbing a torque limiter to mount between my OM603 and the chassis. Unfortunately, there's not a whole lot of places to bolt stuff to the motor.

Engine torque limiter or "dogbone mount"

Proctor750 · #8 02-06-2013, 12:56 PM

All of the mounts seemed to be fine I loaded the drive train and unloaded it with my tech friend looking under the car. When you let out the clutch after shifting to fifth there is a noticable clunk from the rear though..
Are these cars single or dual mass flywheel? I imagine dual since diesel, and my tech budy thinks its the bushings that hold the 2 masses together.
I think its entirely diff backlash, and the only other thread on any site I could find like mine the guy put a junkyard diff in and it fixed the problem. ...
I don't know how easy I could find my diff..

raysorenson · #9 02-06-2013, 01:18 PM

As a person who makes a living building diffs, I can tell you that the number 1 cause for rear diff gear whines is bearing wear that changes gear backlash. Were your backlash so out of specs that you could improve your driveline slop by reducing gear backlash, your rear end would be howling.

What you're likely feeling is the diff twisting in the mounts. The mounts have holes in them to allow free movement of the diff. I go into this in detail in the thread I linked to.

Proctor750 · #10 02-06-2013, 06:30 PM

Quote:

Originally Posted by raysorenson

As a person who makes a living building diffs, I can tell you that the number 1 cause for rear diff gear whines is bearing wear that changes gear backlash. Were your backlash so out of specs that you could improve your driveline slop by reducing gear backlash, your rear end would be howling.

What you're likely feeling is the diff twisting in the mounts. The mounts have holes in them to allow free movement of the diff. I go into this in detail in the thread I linked to.

AHA! well there's certainly no noise so I suppose that rules out that. AND it's possible the guy who replaced his diff which fixed the problem didn't realize it but he PROBABLY replaced his diff mounts too which actually was the problem

Just so we are clear, this movement is much like a half full jug of milk that you slide across a table, or a segway scooter when you try to fight its balancing for you. The more you stay the course (part throttle) the harder and harder the car shakes back and forth. It feels as if the drive shaft is sliding back and forth from the diff to the trans. Or imagine someone flooring it and letting off and flooring it and letting off only your foot never moved.. If that sounds like diff mounts then I'm replacing them immediately. I just figured they would just make noise and maybe some lateral feedback but nothing like this. I suppose the diff is actually moving back and forth taking and giving slack in the driveline.

raysorenson · #11 02-06-2013, 07:05 PM

Yep, that's it. If your diff mounts are the same pt# as the W124 6cyl/diesel diff mounts then I'll sell you a set of poly mounts that I made. Way, way stiffer than stock. Even with those it won't be "fixed".

Right now I'm eyeing action at the motor mount end. My motor rocks around a lot in the engine bay despite having pretty fresh mounts.

With respect to flex discs, I was talking to Revshift about making some flex discs to fit the 190e stuff but they quit returning my calls e-mails. They claim to have a disc made for the '05-06 GTO that should fit the W124's. Stiffer flex discs should help too, but I think the majority of what I'm dealing with now is from the engine rocking back and forth on the mounts.

Revshift flex disc:

Proctor750 · #12 02-06-2013, 08:11 PM

Quote:

Originally Posted by raysorenson

Yep, that's it. If your diff mounts are the same pt# as the W124 6cyl/diesel diff mounts then I'll sell you a set of poly mounts that I made. Way, way stiffer than stock. Even with those it won't be "fixed".

Right now I'm eyeing action at the motor mount end. My motor rocks around a lot in the engine bay despite having pretty fresh mounts.

With respect to flex discs, I was talking to Revshift about making some flex discs to fit the 190e stuff but they quit returning my calls e-mails. They claim to have a disc made for the '05-06 GTO that should fit the W124's. Stiffer flex discs should help too, but I think the majority of what I'm dealing with now is from the engine rocking back and forth on the mounts.

Revshift flex disc:

wow that's cool, how much do they run? I'm wondering if the cases or mounts are different on our cars. I'm guessing the 5 speed Canada cars probably shared the same case as the Auto's just different gearing so the bushings should be the same. I will try looking for a part number to match up.
For you I'm wondering why this didn't completely solve the problem if all the bushing are like new? The car didn't do this when it was new, surely there is something being overlooked?

raysorenson · #13 02-07-2013, 07:46 PM

I checked and it appears that the 201 diff bolts right up to the subframe without a mount. So you're good there:-)

Those flex discs run 130 USD, but again, they don't make one to fit the 201. They had a page on their site where they claimed to be willing to fab up custom discs, but they've removed that page from their site since I asked them to make one. Pretty weird.

Since your car was born a manual (mine wasn't) have you checked to see if that linkage damper thing a.k.a. "dashpot" is worn out? PN 6010701367 It's supposed to help prevent this issue.

Stevo · #14 02-07-2013, 08:32 PM

I have two 240Ds, one with a dash pot and one without. The one with does shift nicer and the one w/o a little rougher but not that much difference.

Nobody else thinks it could be the springs in the clutch disc? My 79 will get to bouncing at low RPM and I have to shift down or she keeps bouncing. I thought it was the clutch disc which only has about 50k on it.

Proctor750 · #15 02-07-2013, 08:45 PM

Quote:

Originally Posted by Stevo

I have two 240Ds, one with a dash pot and one without. The one with does shift nicer and the one w/o a little rougher but not that much difference.

Nobody else thinks it could be the springs in the clutch disc? My 79 will get to bouncing at low RPM and I have to shift down or she keeps bouncing. I thought it was the clutch disc which only has about 50k on it.

But you can order a clutch sprung or un-sprung and it doesn't make a difference once engaged..
The only thing clutch side I can think of would be IF the flywheels on these are dual mass, the bushings holding the masses together could wear out and cause a discrepancy in power being delivered almost like rubber bands.

I didn't realize the diff was a solid mount in the 201's that seems insane, and it still makes a good clunking sound getting into 5th. hmm