Just installed new motor mounts in the 1984 300D. Engine is rock solid at both idle and when revved. When I place the car into gear, I hear a slight low frequency "rumble" when starting out....once the car gets moving the rumble stops. any ideas?

Does it sound like it coming from the motor, the tranny or the rear-end?

Maybe you have some bad bearings?

__________________
'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter

Maybe you have a tiger in your tank

Check the prop shaft flex joints and center bearing.

Sixto
87 300D

It sounds like the growl is coming from the rear of the car.

How do I check those?

I would check the half-shafts. Also, do you know the status of the diff fluid? Might be worth a drain & fill.

__________________
'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter

check the tranny mount

__________________
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

The tranny mount hasn't been replaced since I've had the car (20 years, can you believe it?). How do I check the transmission mount?

Don't even bother checking. Just replace it.

__________________
'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter