I have both the factory assembly manual and the shop manual for the truck (55.1 3600). I cannot find a torque spec for the drum backing plate (where it attaches with 4 bolts to the rear axle with 1/2"-20 grade 8 bolts with lock washers). It seems to me that the torque is pretty high considering that I couldn't turn it by hand and had to jump on a breaker bar to get them loose, but that could be a lot of rust helping to hold on some tight bolts. I doubt the drum backing plates had ever been removed.

I did find the torque specs for the rear axle hub (85-95 ft-lbs), but not the backing plate. One post on here about looking up the torque for a particular bolt (in their case 45 ft-lbs for a 3/8" bolt). In the case of the 1/2"-20 bolt, I found a value of 120 ft-lbs online. This seems like a lot of torque to me, and I was hoping someone else had figured this out already.

Thanks in advance!