MTFCA Forum

My 1923 has started to occasionally make a snapping sound when its under a heavy load,it does it when backing up a incline or on soft ground. The noise is coming from transmission not rear end,any ideas where to start? Both forward gears work fine

One possibility, rear end problems can 'transmit' the sound to the tranny.

Mine had the same issue, banging in reverse, but not forward, (backing out of my shop rolls into sand), sounding like it was thumping under my feet.

In my case the driveshaft roller bearing (among other things) was shot causing the pinion to pop out of mesh with the ring in reverse. It acted fine going forward.

Kurt is right

nearly certain it's either pinion roller bearing failure or differential thrust washer failure

stop driving the car NOW. The ring/pinion are undoubtedly being damaged and the longer it's driven the worse the damage will get (including loss of brakes and further related damage).

You might want to block up the rear end and run the car in high at about 15 MPH for ten minutes or so, then shut it off and pull a sample of the rear axle lube. A suction gun works well for this. You will probably find excess metal debris in the lube. Rotating the wheels by hand, and running it in low and reverse while the vehicle is warmed up and on the blocks may reveal more evidence of what may be wrong. Whatever it is, it won't fix itself.