Outer Limits 4x4 Board

I have an 82 model 45 trayback with a 4 speed (has the handbrake drum behind the transfer case) with a 400 chev smallblock. All works fine except it jams in 3rd when decelerating. If I back off in 3rd and try to downchange to 2nd, it won't budge until I apply positive torque (accelerate a little), then it down changes perfectly. Is this worn bearings? If so, is it a major dissassembly and reassembly? Are the parts expensive and what else should I pay particular attention to or look at replacing as a matter of course while I'm at it?

Also, if it's too expensive to fix, will my BJ42, 81 model 4speed (without handbrake behind transfer) bolt in behind the chev where the previous mentioned 4speed was, or will it have a different bolt pattern or shaft length etc.?
Thanks

The gearbox bolt pattern is the same the only problem is u will loose the handbrake although it should fit onto the transfer as long as they r both split case transfers.
The 3rd gear problem is in the shift assembly in the gearbox fairly common i now of a bloke who replaced the whole lot just to fix the problem.

Sounds like the sincro hub is worn out. I replaced mine (After it locked into second) for around $80. Down side, is that the box will have to come out, and completely apart, so it might be a good time to put a kit through it as well, so ya giiit another 30 years out of it……Could be a can of worms, but might be worth opening it to find out......

5speed !!!!!!!