Nice looking truck Greg, here in NZ , the '54 had an open drive line with 'U' joints at front and rear of the driveshaft. In which case Geoffs reply stands.
If your truck does not have a rear 'U' joint , then the torque tube sounds like it is leaking , which is odd , cause there is not normally a problem there. There is not an oil seal there , dismantling the torque tube is an out of the vehicle job and can be problematic.
I suggest you do a couple of things first.
1. Check the oil level in the diff, if it is over full this may be the cause of the leak.
2. Check the breather on the axle casing is clear.
3. If the diff is overfull, check the gearbox level , cause thats where the extra oil in the diff came from, draining down thru the shot seal at the top of the t/tube. Another fun job.
Let us know how you get on.
