Kawika007

I have a 2003 Tahoe Z71 5 something gas engine (Sorry im not sure) I had a Service 4WD message come on, read the code and then checked the electric output of the Transfer Case Control Module, it was barely 2 amp needed to be 5 (Side note was that i originally had issues with the tahoe changing into 4wd over 45 MPH all by itself which we now know that the TCCM was bad). So i replaced that and the error went away and i installed my new transfer case motor. I put everything back together and then tried to switch it into 2wd from Neutral. It would flash and then nothing would happen. All of a sudden on one try it went into 4LO and wont switch to anything else. I thought i might need to move the vehicle a little bit and move the tranny...well i went into drive and all it did was revvvv the engine, tried Reverse, same thing. Then i put it back into park and it made an awful grinding noise like the gears were catching up to the engine to go into Park. I havent tried it again because of the noise but i have tried turning the key to RUN and then putting the vehicle in Neutral and then selecting my gear, the transfer case motor makes noises but nothing happens. Now that its in 4LO i tried to put it back into Neutral by selecting at the same time 2HI and 4LO but after 20 seconds nothing happens. I tried putting the car in Run and selecting 2HI and then turning off the car, but the transfer case motor keeps trying even with the car off and then fails.
Ideas?

tech2

remove the encoder motor and manually shift the tcase into 2wd. This will allow you to drive the vehicle.

maybe you didn't index it correctly when installed or maybe another issue issue with the system is present. did you plug in the connector without the encoder bolted to the tcase?

Kawika007

We believe that because the computer was sending false signals for so long (previous owner ignored it) that the prolonged use of switching to 4wd at extreme speeds has broken the transfer case. A transmission specialist i trust has said that its broken and needs to be replaced/repaired.

tech2

something is broken but not from sending the computer sending wrong signals.

if the tcase can't perform a shift it stays in the current range and mode. the tcase won't allow a 4lo shift if not in neutral or moving over 5mph. the only moving shift allowed is 4hi and 2 hi...neither of which will damage the tcase.

by removing the encoder and moving the shift **** with a wrench you can test each mode without removing the tcase. if you can't shift it manually, something inside is damaged.

Truckinguy

Ok, I've read many threads here, good info.
My problem is weird, read on...
i have an 02 tahoe LT, 5.3 auto.
Put it In auto 4wd, all was good. Went to put it in 2wd, transfer case would not shift. Would only shift to 4hi.
Tried the usual by disconnecting the battery, pulling fuses etc.
The 20 amp ATC fuse under the hood was ok, until now.
That fuse keeps blowing, here's the weird part...
When I start truck, the transfer case shows it in neutral (red light illuminates on switch)
So I dont think it's the dash switch.
Try to switch to 2wd and fuse blows, and transmission wont shift at all.
I'm suspecting the TCCM might be at fault, or the encoder moter.
Any ideas guys ?
all advice is much appreciated!
Thanks to all!