Stuck in 4 low

[Pooble]

Have an 03 gmc 2500hd that ive been slowly rebuilding and just passed inspection it used to have service 4wd untill i cleaned up the driver side grounds and started to shift fine atleast long enough to pass, until today it shifted by itself into 4low by itself once i turned the truck on now it will not come out even in neutral tried going R-N-D-R-N...etc to kick it back on but no luck, confirmed it wasn't the 4x4 selector buttons, its not pulling any codes at least on my scan tool. hitting up the junk yard tomorrow just going to grab a used tccm, actuator off the front diff and transfer case shift encoder since they are all super easy to pull and dirt cheap at my local junk yard and i have nothing but time at the moment.

 

just wondering if any of you guys have had good/bad luck with any of those parts failing on you and causing the truck to get stuck into 4low/hi or the truck shifting into those selections by itself. and what your fixes and problems were. thanks guys!

Edited February 23, 2024 by Pooble

[06pirate]

My truck is  2006 Sierra SLT 1500 and it did what sounds like the same thing a few years go.  It was the oil pump in the transfer case that had failed.  The pump rotor had eaten through the side of the case, dumped all the oil, so no oil pressure.  That caused it to slam into 4low.  I was only 1.5 miles from home, so I limped it home, and then had it towed to the local dealer.  The oil was a sludgy goo filled with metal particles.  The transfer case was so worn out and torn up inside it was not saveable, had to get a whole new assembly.  I don't know if these model years use the same transfer case, but that's a possibility.  I've read about the oil pumps in these eating into the case, apparently it's fairly common.  Search GMC / CHEVY 2003 - 2006 4wd truck transfer case oil pump problems

 

Some possible info, may or may not apply to your vehicle:

 

https://bobistheoilguy.com/forums/threads/gmc-transfer-case-pump-rub-fix.228633/

 

https://www.merchant-automotive.com/Transfer-Case-Pump-Upgrade-Kit

 

 

[Pooble]

14 hours ago, Pooble said:

bit of an update it popped out of 4low this morning it shifts fine now but  service 4wd its back on the dash, and when i start the truck it starts it seems to pick a random setting(auto, 2hi 4hi/low). im going to check and and change the fluid out before i throw parts at it, double check my ground wires. and take a good look at the wiring and case.  thanks ill look into that to think its a np246 transfer case