99 Silverado with ATC automatic transfer case doesn't engage to 4WD. Need help.

SDNomad · 2003-11-03T16:00:27+00:00

I have a newer body style 99 silverado with a automatic transfer casethat is not locking into four wheel drive. The front axle locks inbecause I placed it in 4WD and put the front end up in the air andchecked. But when I put the rear axle in the air, while in 4WD andmotor running in gear, the transfer case does not turn the front driveshaft. I can hear the encoder motor inside the transfer case runningwhen I push the 4WD and 2WD selector buttons so I assume it isshifting from 2WD to 4WD high to 4WD low to 4WD auto, etc. but thetransfer case doesn't lock up. I don't know if the encoder motor iswhat shifts the vehicle into low gear when you push the 4WD lowbutton, but it does go into low when you select 4WD low. It is easy totell that it is going into low because it just creeps along. Would afront or rear speed sensor cause the transfer case not to lock into4WD? Whatever makes the transfer case lock in or regulates it lockingin, is not working. I do not have a 4WD/AWD service indicator lighton. And all the indicator lights on the 4WD and 2WD selector buttonssay the trasfer case is shifting from 2wd high to 4wd high to 4wd low,etc. My only indication that things are not right is that the transfercase is not turn the front axle. Any ideas? Thank you!

Nov 03, 2003 21 Replies

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SDNomad 22 years ago

Well Ian, You called it on the nose, first time out. You know your stuff. I put the other transfer case in and now I have 4WD. And I checked the front diff fluid and it was completely permeated with metal. You could stick the magnet into any spot of the fluid and come up with a big glob of metal. Now I have to put in a front axle. Thanks again for your help, Doug

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KJ 22 years ago

Seems weird that you would ruin things if you were careful. But I guess I should stop talking of that which I know not!

~KJ~

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