Yeah frizzen I've used Shoe Goo in the diffs, usually the front diff of a TLT, then left the middle axle open & manually locked the rear axle dropping a spider gear between the other two within diff for 5wd. I've also used the Gear Doctor lockers that Bo linked too, but they're hard on stock Tamiya spider crosses... somebody makes a steel spider cross, might be rcbrim?
I think I have a 6x6 set of locker axles that I got from RC4WD yrs ago, they're the same axles in the Eagle Mach wheel loader, RCBRIM makes them? I never used them, still in box, you're welcome to them condor for $cdn, pm if you're interested... as I see you're from Ontario, shipping will be cheap.
I've pretty well retired all my Tamiya trks, too small, too weak... FUMOTEC POWER WAHOO!!!