[Ironhorse427]

Last Friday the wife took our 2003 2500 HD 4x4 (the one with the buttons on the dash to make the shifts from 2WD 4WDH 4WDL ) and the message came across the dash "service 4WD" Well I crawled under it and checked everything out and while it all looks fine and all the wires are still hooked up where they are supposed to be now it wont shift into 4WDL at all dont even make a noise like its trying to shift. And the message is still on the dash. No I have not cleared the fault indicator or reset the system by un hooking the battery so its obvious I still have a issue someplace.
I do need to add a bit of fluid to the transfer case and the book says to use Auto Trak II fluid is that my only option or is there something else I can use?
Another Issue I have with the Transmission is the Trailer Tow mode isnt working any more either ? I can press it all I want but it makes no difference even the little trailer symbol guit coming on in the dash so I am starting to think I may have a bunch of things going on inside there ?
Any ideas on what to try next to cure these issues ?

THANKS in advance for any help.

 

[Detroit Gearbox]

1 Scan for dtc's before you clear any. The message you have is like a telephone answering machine flashing light indicating these is a message. Obtain the message (dtc) first. Then you can determine the service required.
2. Auto Trac fluid is the only fluid to use. It holds 2 quarts. Replace all of it. Do not use a impact on the drain or fill plug.
3. No need right now for shifting into low range. Most people do not know proper procedure anyhow.

 

[125incher]

T cases with auto 4wd 4 buttons RPO code NP8 use auto trac II. t cases with 3 buttons (RPO NP2 or NP1) use 88861800 t case fluid. The tow haul concern is most likely
a broken wire at the base of the shift lever. The whole handle has to be replaced.

 

[Ironhorse427]

Turned out to be a very minor deal. We had a real heavy rainstorm last Friday here (west of us it snowed between 4 to 9 " already) but anyway she had driven through some low spots on our gravel road between the house and the highway and it was a simple case of the connections getting wet where the wires connect to the shift actuator motor. I un hooked them all and cleaned them with electrical contact cleaner and for good measure put some dielectric grease in them to keep any moisture from getting in there for awhile.
It could have been the shift acuator motor itself but I always like to check the obvious first. Once I had them clean and back together it works like a new one againand All is good.
I checked the switch in the shifter handle was a bit trickier once I found that the switch itself was bad it was a simle matter of (instead of giving the dealer almost 200.00 for a new lever and switch button) to just install a nice little round momentary switcb that even lites up amber in the dash and it works really good..
Thanks for the help and advice.
Randy

 

[us7race]

The shift module on the side of the transfer case can go bad. You can manually take it off and use a cresent wrench on it to make sure the transfer case is ok. The trailer or tow haul mode I am not sure. I get my info off of Dieselplace.com Good luck.

 

[JOHNBOY66]

Tow mode first. Before replacing the whole shifter handle remove steering column plastic shroud haves and have a look. It is very common for the wire from the tow haul button to break at the handle hinge. IIRC it is an orange wire. Worth looking into as it could be an easy fix.

Proper fluid in the T Case. If your T Case has an auto mode than you need the Auto Shift fluid. If does not have Auto mode then ATF is fine.

Now to the service 4wd. You need to pull the codes. The switch in dash can go bad. Also the actuator on the T-case can fail. The fork in T-case can stick. The Detent springs can break.