I installed new rear springs, spring pads, body mounts and shocks on my 70 220D I also installed a rear sub frame – rear-end out of a 76 240D in to the 70 220D.

The 76 rear sub frame came out of a car I drove for 2 years it is in good shape.

Now when accelerating I get a slight rumble till I get up to speed, while cruising it is smooth.

The flex disk look ok could this be the problem what else should I check?

It is an automatic.

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1976 240D
1976 240D parts car
1970 220D daily driver

I'd take a close look at the impeller shaft. He could be flopping around a bit. Center support/bearing.

Jay.

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On the road, currently:
'83 300D (German spec.) 168k mi. - - Wolfgang (tucked snugly away for the winter!)
'87 300D 375k mi. - finally went over to "The Dark Side"
'87 300TD 225k mi.
Cannondale 66cm CAAD5 w/Campy/Jamis Aurora
Hujsak Custom Fixie/Landshark Track Shark Custom/Ahearne Custom 29'er

Yes like James said, check the center support bearing on the drive shaft.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Up date
I just took a drive during lunch break it starts at 30MPH the car feals like i have a bad tire
the support/bearing was replaced not to lon ago.

I will jack it up tonight and check impeller shaft and Center support/bearing.

it was not doing this before the swap i did use a diferent flex disk i used one that looked better than the one i took off. I was planing on replacing all the flex disk when i install a standard trans.

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1976 240D
1976 240D parts car
1970 220D daily driver

It is soft like a marshmallow.

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1976 240D
1976 240D parts car
1970 220D daily driver