I just drove my new acquisition home last night and today. It has a definete whine/hum that increases/decreases in pitch as I speed up/down. It's a low frequency (kind of like tire noise), and greatly diminishes in volume if I come off the power. It SEEMED to diminish/go away at 70 or so, but it could just be that everything else is so noisy at that speed the hum is drowned out.

I'm wondering where to start troubleshooting, and HOPING its just a bearing or u-joint. Seems too far back to be trany related (back seat area) although THAT seems to make a slight noise when not in gear as well.

Any suggestions MOST welcome,

Matt

try rotating the tires to the front, see if the noise moves. while you have the rear up, spin the tires by hand and feel for roughness.
pull the diff fill plug, and stick your finger in there and see if you have proper level of oil.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

change the oil in the diff. rotate tires to front. check carrier bearing. check cv boots

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1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it