I have a 99 yukon slt with the rpo8 auto 4wd transfer case and the 4wd is not working... Ive read and read and can not find anything to help me. I know that the front end actuator is good as it is brand new. So yesterday the front output shaft seal was bad on it so i had the driveshaft out so while i had it all torn apart i decided to take the transfer case shift motor out and check its function... it moves when put in 4 hi and 4 lo. So I put it all back together and before i hooked the driveshaft up to the front differential i pushed the 4wd button again and again i heard it shift.....BUT i was still able to rotate the driveshaft even though it was in 4hi and in part...... Ive drinken many beers trying to figure this out and im down right stumped.... any ideas anybody ?
Completely stumped!
- Thread starter cfd641988
- Start date
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if the things you checked functioned and it is shifting but not engaging have you checked the vacuum.. correct me if im wrong but all push button 4wd are vacuum operated so if everything else is working and its not engaging id check that out..
SunlitComet
OBS Jedi-Do Good
did you with the help of some one actually see the front yoke on the t-case rotate several times while moving vehicle forward a little or did you just look yourself before and after vehicle movement?
And no vacuum systems use on these electronic shifters ever.
And no vacuum systems use on these electronic shifters ever.
destroyer1362
A work in progress
If you can still turn the front drive shaft in 4x4 mode and in park the problem is in the t-case. Maybe something inside the t-case is out of wack. When did u notice the 4x4 was out? Weird things can happen, I had a problem with my 4x4 no engaging and this is what I found in my front diff when I opened it. 
SunlitComet
OBS Jedi-Do Good
Destroyer, maybe it snagged when you pulled it apart.
