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Bozeman, MT

1995 Yukon won't do 4 wheel drive

1995 Yukon. Front wheels won't help drive in the snow.
The 4x4 light inside on the floorboard eventually comes on when I pull the lever or push clear forward for LowRange, but the front wheels won't try.
In looking for reasons, I find the front drive shaft is bad.
Need a new u-joint in front drive shaft so that is off.
Jacked up all 4 wheels off the floor. Put it in drive.
The front connector where the u-joint bolts on spins but i can stop it with a stick.
Low range / high range no difference. Still no power getting out the front of the transfer case.

What do I look for? I saw some reference to 'transfer case motor actuator' and push buttons on the dash. Mine has a lever on the floor. I don't know if this model has an electric actuator in the transfer case or not. Maybe vacuum actuator? I am not seeing anything external that looks like an actuator. Maybe inside?

I had a GMC Jimmy years ago and had the mechanical vacuum switch on the transfer case plug up and the hubs wouldn't engage.
I see electric wires going to the front differential on this and the hubs? seem to kick in and out properly.

What is next? Are there pictures available anywhere to see if there is linkage inside or there really is an actuator and I missed it?

Premium,ExMod 2000-03
NW Illinois

If there is no driving force at the output shaft of the transfer case when the lever is in any 4x4 position, then you have a failure inside the transfer case itself. The front shaft is mechanically engaged when the lever is moved internally. The front hubs are always engaged to the front differential, and there is an electrically-activated shift mechanism inside the differential that connects the front shaft to the front diff.

I have had many of those cases apart, and there are a few different possibilities for the issue. But it will have to come apart to be visually inspected to know what the root cause is.

Bozeman, MT
I got a front drive shaft put back in and it seems to work fine.

I did find the splines section on my old drive shaft was spinning, slipping, turning around and around.
BAD. So, that explains why the front wheels wouldn't help drive in the snow.

I don't know why I was able to stop the front connector with a stick.
Working every time now. Must have not kicked in good with no pressure on the wheels...


Milledgeville, GA
reply to ttiiggy
This is from memory - it's been a few years since I had my old 92 GMC 4x4.

The actuators are thermal in nature, making them prone to failure first in cold weather. You can replace them with 1998+ model parts that are mechanical.

I ran into this site while trying to jog my memory. It might get you on the right track: » ··· /106796/
John M - Cranky network guy