2005 Suburban GMT800 NP246 No 4HI, goes to Auto 4WD

[redhat]

Good morning, I have a 2005 Suburban Z71 with 202k on the clock. I had to put a rebuilt transfer case in it. The rebuilt case has a Sonnax case save installed to prevent pump rub issues.

I picked up the truck (clean from Texas) weeks back and when I changed all fluids in the truck, the transfer case was about empty. I filled it back up with AutoTrak II, but the case was too far gone -- bearings felt horrible and the seals were leaking most of the fluid out.

Was pretty careful with the encoder motor, however, now when I shift it into 4HI, it blinks 4HI a few times then by default goes to Auto 4WD. I cannot get it into 4HI. It will shift into 4LO no problem, as well as go back into 2WD. I don't ever recall the t-case having to stay in Auto 4WD.

Is the encoder bad? Or possibly the switch? I have heard that I may have to have the Transfer Case control module re-programmed or reset for the new clutch packs in the new t-case. Has anyone heard of this? For reference this is the NP246 case. Is this a common dealer visit item or something I could do from a Tech 2?

Thanks!

 

[gmcman]

Hard to say, could be your front 4WD disconnect not locking in. It does sound like a transfer case issue if you can get 4HI and not A4WD, but does the front encoder motor operate when selecting A4WD?

 

[TJBaker57]

Do you have an OBD2 adapter such as those used for apps like Torque Pro or OBD Fusion??

I have an 05 Yukon, 5.3 LM7 amd the 4 button 4WD system.

 

[Mooseman]

With the truck OFF, press each switch numerous times to try and clean the contacts inside.Then, with the truck in RUN but not running, put it in A4wd, you should hear a high pitched whine from the front, which is the disconnect actuating. Then going to 4hi, you should hear the transfer case shift. If it doesn't, could be the encoder motor or the transfer case is having a mechanical issue.