to start off here are the specs. the front case (crawl box) is from a 79 or 80. but i messed up the low speed gear so i picked up a later forward shift case and used ONLY the low speed gear. the rest of the gears were out of the early case. i am also using a TG adaptor kit.
when i first got it installed, it seemed to work, except it was difficult to shift the crawl box. i just figured it would "break in". i went to take it on a trial run, made it a block from my house, and i heard a slight raspy/rattle sound and BAM! my tires locked up and the cases were smoking. when i went to take off again there was a lot of resistance. so i parked it, took the shifter off the crawl box, and cycled shift rail back and forth. it drove fine for a few minutes, then did it again, again, then again. got really smokey. any ideas?

 

Do you have gear oil in your boxes? Sounds like your bearings are seizing from heat. I would also guess that you have now smoked your box, and need new bearings.

 

I wouldn't mix-match parts from different used machines unless absolutely necessary. Even if everything was identical at time of production mechanical parts wear unique to each other. This is one of the torture test they do with handguns.

 

If it were my truck, Id drop the cases and take them apart to find the damage. Front the sounds of your endeavor, it should be pretty apparent.

What did you do to mess up the low speed gear? Is it the crawl box or the tcase thats locking up?

 

Pull em apart and take pics

 

You are going to need to pull them apart.

Some 79-80 input shafts need to be clearanced for proper engagement. They aren't a build it and go.

 

If you diddnt grind the splines down its broke dude. But thats only the tranfers off the 4 speed. on the l43 the gear retains the coupler. On everything else it is held in place with the snap ring.