Just bought a 93 FD about a week ago, drove it all the way home from sacramento no problem. Yesterday it started making a thumping noise while moving. It sounds almost as if it has a flat tire (although it does not) with a thumping noise and feel. The sound continues without the transmission engaged and starts at around 6 mph. Anyone have any ideas on what it could be or what I should check for?

 

could be anything without isolating it down further.
I have seen Fd's that have a bad brake shim clunk when braking.

 

Could be worn axles in the rear. Check the rubber boots for cracks and wear. If they are, look into the boot to see if your axle has grease on it, but if the boots are worn, you usually want to replace the whole axle. This is just an idea but jack her up from the back and see if anything looks off, pull the wheels off and give everything a good look over, see what you can find.

 

Get it level and on jack-stands on the pinch-rails so there's no weight on the suspension. Make sure the car is solid and stable.
*Get a big breaker-bar and socket and make sure ALL the bolts for the Power Plant Frame (PPF) are tight.
*Closely check the driver's side (left side) motor mount. Known to fail even on relatively low mileage cars.
*The Differential bushings/mounts are oil filled. Look up closely at them for signs of leakage.
*There are six pillow-ball bushings in the rear suspension that are notorious for getting noisey, but it's usually characterized as 'knocking' associated while going over bumps etc.
*Check shock mounts and all suspension components closely.

 

Ok well the sound is coming from the rear end only, thanks for the advice ill jack her up and give it a once over see what i can find.

 

Sounds like it could be the pillow *****. FD's are famous for that.