Transmission or tranfer case? Electrical or mechanical?

AaronandAlicia Dailey · December 7, 2022

OK everyone I want to give thanks ahead for any advice and help.

Truck in question= 2003 Chevy Suburban Z71, 5.3 L Transmission= 4L60-E

So the story started when I was going down the road at about 50mph in cruise control, when suddenly I heard the engine begin to rev up. I hit the brake to take it out of cruise control and the engine stopped revving up. Apparently I lost transmission of power from the engine to the wheels because no matter what gear I put it into now, I get no movement from the vehicle. No reverse and no D1, 2 or 3. When I put the vehicle in park and attempt to push the vehicle it will not roll. When placed in any other gear I can then roll the vehicle freely.

Before this happened: Since owning the vehicle 4x4 has always been shifty.....hehehe...sorry couldnt help it. I have the model where there are 4 buttons with lights the buttons are located left hand of dash near the turn signal. When I first got the truck sometimes it seemed like it didnt want to switch between gears. for example I would have to hit the button multiple times before it would switch and even then it seemed like it hadnt really switched but the lights would indicate it had. Most of the time the light for the button I selected would flash multiple times and then return to previous selection. Often times after turning the vehicle off and then returning to vehicle to go somewhere I would find that the light has switched back to a gear that it wasnt in when i left the vehicle. It seems to favor 4x4hi. As of lately I havent been able to get the lights to switch at all. It seems to be stuck in 4hi permanently.

I have tested the 4wd switch and its fine.

I tried unhooking battery for half hour with lights on to reset PC. I then reconnected battery cable and turned vehicle on but not start it. Then I pulled a bunch of fuses and plugged them back in. ( seen it in a video and the guy said it was supposed to wake up the TCCM) Well that did nothing.

I have the truck off of all wheels right now and was trying to figure out if the transfer case is stuck in neutral. With the truck in drive as I turn the rear draft the front moves also. I am assuming that means it is in 4wd. But should I have someone hold the front drive shaft while i turn the rear drive shaft to confirm its not just from friction or something.

I actually have the front drive shaft partly out right now in an attempt to get at and remove the shift motor and manually put the transfer case into 2hi.

I am also considering changing out solenoids. I have gathered it is unlikely the shift solenoids. Is it possible it could be one of these:

1 * EPC (Pressure Control) Solenoid

1 * PWM Solenoid

1 * Manifold Pressure Switch

1 * TCC Solenoid w/Harness

Another thing I suspect which would be an easy fix is the transfer case fluid level. I removed the fill plug and nothing came out. I can tell it has been leaking. I would have already topped it off but I have been stuck at home (no running vehicle lol). Could low fluid cause this issue? I hope that's all it is lol. Anyways I got a ride to the store tomorrow and to look at a back-up vehicle. Anything you guys recommend to grab from the parts store while I'm in town tomorrow?

What would be your guys recommendation on how to solve this problem and fix it?

All help is appreciated.

thanks in advance,

Aaron

elcamino · December 7, 2022

Sounds like the transmission is shot, or possibly th transfer case is stuck in neutral. What color is the fluid? Anything but cherry red is abnormal.

Its normal for the vehicle to not move in park. The parking pawl locks the transmission output shaft (connected to rear driveshaft) when its in park so the vehicle cannot move with the rear wheels on the ground. Has nothing to do with the operation of the transmission.

Edited December 7, 2022 by elcamino

AaronandAlicia Dailey · December 7, 2022

2 hours ago, elcamino said:

Sounds like the transmission is shot, or possibly th transfer case is stuck in neutral. What color is the fluid? Anything but cherry red is abnormal.

Yes it is red

2 hours ago, elcamino said:

Its normal for the vehicle to not move in park. The parking pawl locks the transmission output shaft (connected to rear driveshaft) when its in park so the vehicle cannot move with the rear wheels on the ground. Has nothing to do with the operation of the transmission.

Thank you, I understand that it shouldn't roll in park. I only mentioned that to explain that when I put it into any other gear it rolls freely. I thought that info may help in the diagnosis.

While I have the vehicle off the ground is there any way to confirm whether or not the transfer case is in neutral?