No 4WD low lockup

[DC101]

2005 5. 9 3500 6 speed NV 5600 on dash electric 4wd selection. I use 4wd high a lot but rarely low lock, now it won't lock in just flashes the light. Any sugestion were to look first? Wiring to unit on the bottom of the transfer case is intact.

 

[MChrist]

I know that on my truck, you have to have no load on the drivetrain and be moving slightly for it to engage. I found the best way was to be in 4WD, moving a few MPH, switch to 4LO, and pop my auto trans into neutral while still moving slowly.
Have you tried that?

 

[JFought]

in my truck i have to be in neutral, with no speed then it engauges

 

[mwilson]

Same as above, sometimes you have to move the truck a little to let the shift collar slide. If the light is blinking it is trying to engage.



Mike.

 

[04blackcherry]

Trans in neutral. Speed less than 2-3 mph. Flashing just means you haven't met the computers criteria for putting the TC in low.

 

[DC101]

Thanks, tried all that and even put the truck up off the ground ( all 4 wheels ) reverse/ foward and turned by hand. No low lock. Next I guess I'll drain the transfer case and take off the actuater. Anybody have a diagram??

 

[04blackcherry]

I missed one. Neutral is for automatic transmissions, a clutch signal is for manual transmissions. I just looked in the Service Manual. There are 4 pages on the TCCM (transfer case control module).

Doesn't look like there is much in the book with diagrams. The NV273 does have a Mode Sensor, the Selector Switch, and the Shift Motor (actuator). The mode sensor monitors the shift motor's shaft position. The switch supplies various resistance to the mode sensor supply voltage pin and the mode sensor output. The resistance for 4 Lo is 1050-1450 ohms.

I have this same set up in mine. It's all good until stuff like this happens. I grew up with transfer cases that had 2 manual shifters.

Sounds like if the shift motor is good, it's the communication from the TCCM. The TCCM is asked to do the shifting by the selector switch. Seems the mode sensor knows what you wanted from the selector switch and verifies it at the shift motor. The TCCM tells the shift motor what to do (supplies the power). I don't see anything about testing the motor.

 

[DC101]

04 blackcherry, Thanks for the post, never thought to consider that the TCCM could be a problem, I always had the manual shifter. I'll check this out, thanks again.