I drove my '41 coupe home from the body shop yesterday. I finally got all the areas repaired that were damaged during shipment to me last spring. As I was leaving the shop I shifted into low, and as I pulled out on the road I noticed a loud clunking sound that seemed to come from the center of the car. I was able to shift to 2nd, and the noise went away. I drive home (about 20 miles on back roads) without any further noise. I parked the car in front of the garage and shut it off to go inside and unlock the garage. A few minutes later as I was putting the car inside, I attempted to back up, and the car wouldn't move as I let out the clutch. I moved forward slightly and tried again. Again it wouldn't move ( I checked and the emertgency brake was off). On the third try I heard the clunking sound as I let out the clutch and the car moved backwards. When I shifted into low and let out the clutch, I heard the sound again. Diagnosis is not my strong suit, but my guess is the u-joint. Any thoughts?
Thanks,
Sid

From your description that would be the first place that I would look. Particularly if that is where the noise came from. You should be able to unbolt the ball joint and slide it back so you can rotate the "U" joint for inspection.

Sid,
You may be able to rock the car back and forth enough to cause the sound again. Without the sound of the engine and being outside of the car often helps pinpoint the origin. Drive train noises can be carried up and down the length. It is common to think it comes from one place when in fact it is another. It is the gremlins at work again.

Thanks guys. I may have gotten lucky! I jacked the car up and had my wife move a rear wheel back and forth while I listened to the noise. It appeared to be coming from the front of the driveshaft, so I removed the ball and pushed the sleeve back to expose the u-joint. I found that one of the 4 bolts that hold it together was loose inside the ball assembly. It is all banged up, and the lock plate for that side is missing. Guess that's why the bolt came loose! I see that Filling Station sells a kit with the bolts and lock plates, so I will order the kit. After I get the u-joint bolted together again I assume I'll just need to look for any looseness. I also assume that the u-joint gets its lubrication from seepage from the transmission - correct?
I appreciate the help,
Sid

I would put new seals in the ball and new packing in the tube were it slides.
You need to put oil in the ball before driving. Your repair manual will tell you this. My 52 it goes in one of the four bolt holes and my 37 it goes in the bolt hole for the ground strap.