W124 300D drivetrain vibration at 1500rpm

[petermerle]

My recently acquired 1987 300D ( manual ) has this very harsh drivetrain vibration at about 1500 rpm ( 30km/h in 3rd , 40-50 km/h 4th and 55- 60 km/h ) when slightly loading the engine. It does not do this when in neutral or when vehicle is freehweelin at these speeds. Couplings are good and engine /gearbox mounts have been replaced to no avail. There is however no propshaft vibration damper on the car - ( not sure if there should be ?? ) - could this be the problem. Merc don not sell the vibration damper for this model - I suspect it comes with a complete new propshaft. Any suggestions
Peter

 

[BlackC55]

Have a look at the centre prop bearing/bush

 

[240D 3.0VNTi]

Thats called lugging. You should keep the engine speed above 2000rpm when you are moving in gear. These aren't truck engines with a 2800rpm redline, they need RPMs to make power.

 

[petermerle]

its not lugging - You can load engine at 1200 rpm it does not complain , at 1500 it hits a resonance peak - My 3 OM617 5 cylinder vehicles do not do this , its defininetly feels like some uncontrolled torsional vibration.

IS this vehicle supposed ( 300D manual ) to have the vibration damper ? EPC says part does not exist , however I suspect it comes part of the driveshaft.
PEter

 

[television]

I would check the prop shaft u/j's and bearings as black says, the engine mounts could also do it if worn as it puts the drive chain out of line

 

[petermerle]

W124 300D drivetrain vibration

I checked them and all is fine , no play !
Peter