1970 280SE: Vibration in High Gear:Automatic

[bugpartslou]

When my 280SE goes into the last gear I feel a vibration. Thought it was the driveshaft (it did have a bad carrier bearing) had new u joints installed and shaft balanced, vibration seems to be there in high gear only (last shift) can't feel it as it shifts up through the gears, any thoughts?

[Tomguy]

Just a thought here, and hopefully trying to keep from opening the trans. How are your engine mounts? In final gear in these old Benzes there's no overdrive, so the engine is "Directly connected" to the driveshaft. The trans won't absorb a bad engine mount as well, nor will it absorb an off-balance engine, bad trans mount, etc. I assume your flex disc has been ruled out.

[bwostosh]

I would and usually do,
put a small bottle jack under the passenger side trailing arm under the axle tube, (on level ground) raise the tire 1/2" and have a trusted assistant run it up through the gears.
you can then check those vibrations.
It may show up at a different speed.
I've had them over 60 (short burst) this way.

Easier to find vibrations by isolating car from the road.
I've taken the tire off to isolate a vibe.

do check the mounts too,
all rubber parts are suspect.

[bugpartslou]

Thanks, gentlemen. Looks like I have some checking to do over the weekend.

[Tomguy]

Originally Posted by bwostosh

I would and usually do,
put a small bottle jack under the passenger side trailing arm under the axle tube, (on level ground) raise the tire 1/2" and have a trusted assistant run it up through the gears.
you can then check those vibrations.
It may show up at a different speed.
I've had them over 60 (short burst) this way.

This may be a good method to check but I would STRONGLY advocate:
Chocking the 3 remaining wheels, front and back;
Using a large base jack stand instead of just a bottle jack;
Ensuring you have plenty of space in front of the car in case of a VERY bad situation.