okay so i own a 2000 GMC ext cab 4x4 z71, first thing that happened was the rear diff exploded in my driveway, it locked up and i gave it gas and the pin broke, and i had to replace it with a new 373 Posi ( and yes it was the same ratio that was in there before ).

so, since then i have replaced the diff, pinion seal, and housing seal. everything moved great, with no binding. i drove it for 100 km's and then..
it made a huge clunking noise when it went to shift from first to second,
so then first thing i did was get it towed home before, a case exploded or anything.

so it was brought home, and first thing that came to mind was that it must be a shift solenoid in the Tranny, well i have a scanner put on the truck and no Tranny codes came up.

so since then i have checked, the rear diff for files and or shaving of metal, and it came out okay, then i have removed the front drive shaft to see if the front diff might be binding.

so now the front shaft is out and this is where i am left... the shafts out up front and its still wanting to not shift and i am afraid to force it and blow a case,

so any suggestions as to what it might be or a chart to self diagnose it to get to the problem..? it cant be the rear diff,

so its got to be the transfer case or the front diff..?

any help would be greatly appreciated as the truck has been parked for two weeks and would like to get it figured out so i can go buy the parts bring it home and repair it.

i am a new person to the forum so instead of emailing me or pm me, please just comment below.

 

Wow man, sounds pretty bad.
I honestly don't have a clue, but I have a few friends that might know what's messing it up. I'll check with them and see if I can help you with it at all.
Hate to see a truck sitting.
Good luck in getting that fixed.

 

okay check with them that would be greatly appreciated any one else??

 

If you put your front drive shaft in and don't lock the hubs try to turn it and that will turn your transfer case if everything sounds and feels fine then it would be safe to assume you have a transmission problem.

 

My brother just blew his rear end up last weekend, same as yours. Replaced it with same gears just a new locker instead of the g80, come to find out his wont shift into 3rd or 4th so his tranny is messed up. Sounds bout like yours if you ask me

 

Check to see if its the transfer case. Put it in neutral and see if you can turn it by hand. I had an 94 that locked up when the chain broke.