New transfer case problem
 

2004 GMC Sierria 1500 4wd with the push button 4wd selector

I just had the transfer case replaced and now I have a couple problems:

1) It wont shift to auto-4wd
clangs/bangs when trying to shift to 4hi, doesn't end up shifting
Clangs/bangs when trying to **** to 4low, does eventually and causes the truck to lurch. and does the same while trying to get back into 2wd

2) the auto-locking hubs won't unlock. the front end stays engaged, but isn't in 4wd. front shaft spins while driving but when the truck is lifted off the ground, only the back spins. I know this isn't normal, the front tires usually free spin when i have it off the ground, instead of it being connected.

I've tried driving in reverse in both 2wd and 4wd to try getting everthing back in sync. I've also shifted the transfer case into neutral and letting the truck roll backwards. I've also tried disconnecting the battery to reset the electronic aspect of the system.

Could something be connected wrong or maybe there's another way to reset everything? The new transfer case is a re-manufactured one and it was tested before being shipped to me.

the thing to do would be to clear all dtc , test drive and then see what resets in the transfer case control module. Then diagnose for those dtc.


Lacking a scan tool...I would disconnect the electrical connector and then the encoder motor from the tcase. put a wrench of the end of the shift shaft and manually move the t-case to each position. it if operates normally and can be turned with moderate pressure by hand...the tcase is probably ok.
not sure if its even possible but could the encoder motor get indexed wrong during the install?

it could have very well been indexed wrong. the t-case was literally just swapped out. is there anything specific that needed to be done?

I've never had to index one. you could take apart the old one and learn how to do it.


did you try my suggestion about moving the tcase selector manually and then test driving?

Yeah there isn't really a way to index the wrong. The splines on the encoder only go on one way, and a new encoder comes already in 2wd mode. You can't install the encoder motor until the "shift shaft" and encoder motor splines are aligned to 2wd.

So that's what I would do. Scan for codes, check that the encoder motor is 1) bolted in, 2) is even working, and 3) figure out why the front axle is constantly engaged.

Sounds like you have a bum encoder motor and the truck is actually in 4wd, which is why the front axle is engaged.

I've talked with the manufacturer who rebuilt the case and i'm sending it back to them. The mechanic who installed it did multiple tests trying to figure out what is even happening and everything seems to be normal with the exception that the transfer case is making a lot of noises.

Hopefully they'll send me one that works correctly. Thanks for the advice everyone.