No 4hi/lo in reverse, only in forward gears

[Nalifornia]

What's up boys? I have a problem. I have a 00 obs Yukon Denali. I put the pin hole in my first transfer case. I picked one up that was rebuilt 2 years ago( end of 2017), from Jasper engines and trans, but I found it in a escalade at my junk yard. Anyways I put it in and my 4 wheel drive worked again, and since it was a rebuild it was fixed as to not get the infamous pinhole leak. I thought it was going to be perfect. I took it to the sand and sure enough, 2 hi, 4 hi, 4 lo, all worked great. Or so I thought. Turns out that if I get into a sticky situation and need to back out, my truck decides it's only 2wd again. And I mean leaving it in 4 Lo, and selecting reverse, only rear axle spins. Same with 4 hi. It's a push button transfer that I'm probably going to ditch the push button for a DIY manual selector. The t case selector is electronic controlled, but you can move it manually if you do some work, but the transfer case itself is vacuum operated. Would a vacuum leak or something be causing reverse to malfunction? I got stuck 3 separate times last night in the sand because of this. It seems to be a pretty rare problem, and nobody has been of any help. So I'm bringing my problems to you guys. What do you think it could be? Any help is fully appreciated. Thank you guys.

 

[OR VietVet]

I looked all over and came up with this. The TC does not care if forward or reverse, it is an in/out component. Rockola1971 hopefully will chime in.

"YEEEEESSSSS!!! After dealing with it for 3 years, it was fixed. A little history...it started in 2013 when snow plowing I blew apart the TC on my 04 Avalanche 2500. Rebuilt at trans shop, new housing included. 4x4 worked fine. 8 months later TC failed and it was rebuilt under warranty. Right away, no 4x4 in reverse. Over the next 2 years they had the TC apart 4 times and swore to me there was nothing wrong with it. I replaced the switch in dash, 4x4 module, encoder motor, actuator, complete 4x4 wire harness. All ACDelco parts. After plowing this past Winter with no 4x4 in reverse I'd had enough. I took it to another trans shop that has stellar rep. I've used them before but they are 35 min away and that's a pricey tow. Kicking myself over that to this day. They went over every part in the TC with a micrometer. Turns out almost every part was a few thousands off. They think the second rebuild was with the wrong kit. GM makes another TC that is almost identical. Just a little off. Bottom line it was the TC. Sidenote: If you have the 4 button TC, don't use the AUTO button ever. It's a bad design by GM, there are 11 clutches that engage when you use AUTO. If you are in the close to NJ take it to Wayne Transmission."

 

[Nalifornia]

I looked all over and came up with this. The TC does not care if forward or reverse, it is an in/out component. Rockola1971 hopefully will chime in.

"YEEEEESSSSS!!! After dealing with it for 3 years, it was fixed. A little history...it started in 2013 when snow plowing I blew apart the TC on my 04 Avalanche 2500. Rebuilt at trans shop, new housing included. 4x4 worked fine. 8 months later TC failed and it was rebuilt under warranty. Right away, no 4x4 in reverse. Over the next 2 years they had the TC apart 4 times and swore to me there was nothing wrong with it. I replaced the switch in dash, 4x4 module, encoder motor, actuator, complete 4x4 wire harness. All ACDelco parts. After plowing this past Winter with no 4x4 in reverse I'd had enough. I took it to another trans shop that has stellar rep. I've used them before but they are 35 min away and that's a pricey tow. Kicking myself over that to this day. They went over every part in the TC with a micrometer. Turns out almost every part was a few thousands off. They think the second rebuild was with the wrong kit. GM makes another TC that is almost identical. Just a little off. Bottom line it was the TC. Sidenote: If you have the 4 button TC, don't use the AUTO button ever. It's a bad design by GM, there are 11 clutches that engage when you use AUTO. If you are in the close to NJ take it to Wayne Transmission."

Ahh if it is the transfer case I'm just gonna live with it for now. I want to swap the whole engine and drivetrain anyways. I want to go with a 5.3/4L80/ with a 2500 rearend and front hubs. Not gonna bother pulling the transfer just for another crappy np246. Thanks for your reply man. I appreciate it.

 

[OR VietVet]

Be aware that it may not be the TC but this is what i found. When you shift to reverse does the 4x4 lights stay on or do they go out? It may be something as simple as the switch.

Like this: https://www.rockauto.com/en/moreinfo.php?pk=320327&cc=1440055&jsn=2363

Or this: https://www.rockauto.com/en/moreinfo.php?pk=1354699&cc=1440055&jsn=2366


I very much doubt it could be the encoder or the module. I would also check all related wiring.

 

[Nalifornia]

I've changed the encoder motor already, as well as the front diff actuator. Wiring issue wouldn't surprise me though. I've had this pig in two feet of mud on a few occasions. I can sort of live with it. If I get stuck someone is usually in radio distance lol.

 

[Nalifornia]

My switch is stupid, which is why I'd rather do a manual t case selector. There seems to be lots of problems with the push button style. But the switch works because I can hear the relays click in the dash. When the encoder motor broke the switch would get pushed and I would hear the relay, but then the encoder motor wouldn't move so the relay would click back a second time. It's not the switch though because the relays are working how they should now again.

 

[alpinecrick]

Do the Denali's of that era have an actuator on the front axle?

 

[alpinecrick]

Do the Denali's of that era have an actuator on the front axle?

Edited: Answered my question, it does have an actuator. Almost sounds as though the actuator is releasing when reverse is engaged. As mentioned before, are the switch lights blinking when in reverse?