I have a factory PCM programmed for a 6.0L 4L80E NP241 combo. Having an issue in 4 low. When I engage the transfer case in 4 low it won't shift out of 1st and acts like its in limp mode or something. I rarely use 4 low so I didn't notice this problem before. Originally when I got a reworked harness, it had the two plugs for a 2wd VSS. Since my 4L80E is a 4x4, the VSS ports on the transmission are plugged. Since the VSS is suposed to be plugged into the transfer case on 4x4s, I cut off the plug, put the correct one on for the NP241 transfer case. Been working great in 2WD and 4 high.

I have done some reading about this problem and some people run some sort of switch to compensate for the problem. Some people install a reluctor ring on the tail shaft for a signal. And it looks like some people run a 2wd tune. Obviously the guy who did my harness and PCM sent a 2wd harness and I have a 2wd tune. Would an inline VSS be the way to go or can I set up some sort of switch when 4 low is engaged?

 

Is 4wd enabled in the tune? If not, That may be all you need.

 

No it's not. Does anyone have an HP Tuners file for a 4WD 4L80E?

 

Sorry, I don't have HPT.

Jeff

 

Digging up an old thread.....

Did you ever get a solution?

 

I have the same issue. Have you figured out the problem?

 

If anyone in this thread is making the change from an AutoTrac t case (246 for half-tons) to the 241; there are wiring changes that need to be made at the TCCM: transfer case control module

your truck needs to know it's in gear reduction or it will never see the MPH needed to grab another gear. Your speedo will also be incorrect

https://www.fourwheeler.com/how-to/t...r-case-delete/