I was up in Tahoe this weekend and it was snowing and icy conditions so I pulled her into 4hi and she kept popping out, I tried probably 30 different times throughout the day and she'd pop out every time. No noise or anything, I slowed and put her into 4lo just to try and she locked in no problem and didn't pop out once.

I've never been rough on her or anything and she's only been in 4wd in snow/ice maybe 3-4 times each winter.

 

One draw back of the manual linkage. Probably some ice/snow packed up around the linkage which caused the lever to not shift solidly into 4 hi. Just a guess on my part but sounds like what happened on my old Chevy some years back. It was a gasser with 4x4 and used as a plow truck and occasionally I had to heat it up in the garage to get the linkage thawed out to allow proper shifting again.

JM02 worth

 

Thanks DH, I wish it were that simple. I tried it after coming out of the Mountains and still nothing in High. It pulls into High and it will stay there if I hold it, but if I let go it pops out eventually (1-3 minutes).

 

The linkage is not allowing to go all way into 4H. Sometimes it is external blocking or hitting linkage and pushing out when under torque. Next on internal is rust build up on shift shafts and binding during shift. Damaged shift lever or splines damaged on components.
I would look carefully at linkage for problem.
I would try shifting and trying to get moving lever to travel futher with help from underneath.
You did not say popped out under extreme pressure, so would rule out driveline/tire issues.
I get here then probablly gonna have to come out and down for visual inspect. It is difficult for internal problems to hide.

 

I will crawl underneath when weather permits to check it out.

I should add the 4 Wheel light does come on with out flashing and remains on until it pops out if that helps diagnosing. It doesn't feel like 4hi when it's pulled back so I don't think it's ever engaging.

 

Well I just got it locked in, put the tranny in neutral at a complete stop?

4hi should be shift on the fly and it has operated that way in the past?

Another oddity is that it should be difficult to grab 4wd at a stop due to spline alignment but it slid right in, must have been lined up perfectly?

I'll try it again on the way home to see if it pops out again or not.

 

Guess I will have to climb under anyways, tested again on straight road shifting to 4hi while traveling 25mph, will not hold 4hi.

 

My 2005 is going into 4X4 without a problem but when it is engaged, transfer case is making alot of noise. No visible leaks under truck or on underside of truck. Need to get up underthere and check fluid level in transfer case. Thankfully I have 7year/100K miles extended warranty if it is going up.

 

Okay new updates, on the way home, dry roads (Straight of course) I put it into 4hi it is engaging but it's not holding it. I know this because at two different intersections I made a right turn with it engaged and I could feel it binding up. Don't worry as soon as it started to bind I stopped, straightened the wheels pulled it out of 4hi and then proceeded. Whatever it is it has to be whatever holds it in 4hi, again there is no detectable noise associated with it disengaging by itself.

 

Maybe you just need to adjust the shift rod on the tranfer case.