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Discussion Starter #1
My 86 2.5 diesel 5 speed likes to jerk violantly back and forth the most in low 3rd gear. Usually after a gear change from 2nd to 3rd. The colder it is the worse it is. The longer you drive it the more manageable it is. But no matter how I finesse the accelerator pedal, trying to calm it only makes it worse without letting off completely, or downshifting and getting back into 3rd at higher rpms. It feels like the more low end torque applied, the worse the effect. I have read several threads with no conclusive evidence of the cause. I have checked both guibo's (flex discs), center bearing, and so on. There really is not any play and they appear new. Another thread mentioned something about a butterfly valve? I don't know if they are talking about the throttle body valve or what, but I can't imagine this could be the cause. The only lasting idea I fear may be the culprit is someone replacing their Diff with a junkyard diff and the problem going away.... I can't imagine any amount of back lash that could cause this much jerking in the driveline. Any Ideas?
 

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1974 280C 1991 190E 1986 E-150
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Do you let it idle till 80c? Or just get in and drive? I've got an '84 190D 2.2 non turbo, and I have noticed similar issues, but only if I let the clutch out too early and it rocks about wildly. Have you tried keeping the clutch in a lil longer during gear change?


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Discussion Starter #3
Well cold fluids certainly exaggerate it but even once warm if your not careful it will be like your fighting a gyroscope on a segway. To me that Indicates looseness in the driveline. My only guess is the diff, I read one other thread and the guy fixed the issue after installing another diff. I was just hoping there was another explanation
 

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1974 280C 1991 190E 1986 E-150
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Have you checked the U-joints in the driveline? If it has it, may be worthwhile to change those first. Cheaper than replacing the rear end.


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Discussion Starter #5
I don't even know where I would find a matching rear end for this car.

The drive shaft seems fine as far as center bearing and U-joints. I'll check again.
Another interesting theory is the clutch or clutch springs... I may just put a new one in anyway and see what happens..
 

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1984, 201.122, OM601.921, G717.410
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It is very easy to check drivetrain play. Place chocks at the left rear wheel. jack up the right rear (drive wheel), put it in gear, release emergency brake -- then manually try to rotate the wheel in each direction. See how much play exists.

I have a bit of the same problem on my vehicle. Despite a fully depressed accelerator pedal, the engine does not work to produce continuous full torque. I suspect the problem is in the injection pump servo/governor. Basically, it would not be sufficiently integrating (I), or have too much gain (P). Read up on PID loops --
PID Controller - Wikipedia
Sorry, I don't yet know how to adjust the injection pump.
 

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Discussion Starter #7
It is very easy to check drivetrain play. Place chocks at the left rear wheel. jack up the right rear (drive wheel), put it in gear, release emergency brake -- then manually try to rotate the wheel in each direction. See how much play exists.

I have a bit of the same problem on my vehicle. Despite a fully depressed accelerator pedal, the engine does not work to produce continuous full torque. I suspect the problem is in the injection pump servo/governor. Basically, it would not be sufficiently integrating (I), or have too much gain (P). Read up on PID loops --
PID Controller - Wikipedia
Sorry, I don't yet know how to adjust the injection pump.
Alternately you could put the car in gear and move the flange at the diff with your hands. That would eliminate play in other parts like axles wheel bearings lugs etc.

Well the good news is I have to rebuild my ip so ill let you know if that affects anything.
 
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