Grinding Noise In Transfer Case

[CMXIII]

I have 00 Silverado with the Auto-Trac T/C. The service 4wd light came on however when it came on it only resulted in the inabilty to transfer out of whatever mode i was in (2hi/4hi/4lo/auto) and as soon as i turned off the truck it would go off. One day i was driving the truck on auto mode and it started grinding but it stopped after i switched to 2hi. Now everytime that i drive in auto mode at speeds above 55mph it grinds only when i press or depress the accelerator pedal. Any one have any clue??

[tbplus10]

Sounds like a bearing going out. Have you changed the fuid since the noise/problems started? The original light could be to tell you theres to much metal on the sensors. If not I'd recommend changing the fluid and screening it to see how many metal particles you have. My guess is a lot. Unfortunately transfer case problems dont diagnose well, they usually have to be opened up to find problems.

[CMXIII]

I changed the fluid before the light came on. However, it still came on several times and it does not register a code on the ECM. I changed it 4000 miles after. It still comes on everynow and then.