Drive train "thrum"

[1976300d]

I have new tires, flex couplings, center carrier bearing and support bracket on my 1976 300Dand yet there is a definitive "Thrum" as speed increases the "Thrum" diminishes. I have not yet tried to have the driveline dynamically balanced. I do not see irregularities in the driveline (obvious loss of balance weights) and my transmission dos not leak a drop. I have long term concerns that the "Thrum" may create issues as time passes. When I purchased the car the carrier bearing support rubber was degraded and mostly absent (nothing holding the bearing). The vibration was reduced with the introduction of the parts previously mentioned but not completely.

Any suggestions would be greatly appreciated.

[W.L.SOON]

Hi guys! My 1972' 230 also has this quite minor but noticeable vibration in the 30's. Drive slower or picking up speeds eliminates it.I've replaced the broken centre support mounting and the bearing;but I've yet to replace my flex discs:they're old and as hard as rocks!!! Probably,in my case at least,hopefully they're the culprits;don't know about your case tho'.....

Well,just a bit of rambling from I.Hopefully you guys could share your thoughts/comments with us.Thanks a lot! BYE for now and GOD BLESS!!! :) :) :)

[pch2021]

make sure that the flex discs are torqued properly. Also, make sure that the differential mount is still OK.

finally, check the transmisison mount on more time to make sure it wasnt put on backwards.