Picked up a '99 Yukon, 4x4 and ABS issue

[johnjk07]

Just picked up a 99 Yukon with 134k on it for $4k, was hard to pass up. Has some surface rust due to salted roads, but interior looks spotless.

Anyways, I've noticed the 4x4 behaves strangely. If I leave it on Auto 4WD, sometimes I'll be driving on clean asphalt (seemed like when I was going uphill), and it felt like I just shifted hard, like the 4x4 had engaged.

Also, I shifted into 4hi while doing 55MPH, and the whole thing felt like it was fighting itself when I tried to accelerate. This was in blizzard conditions, not try surface. Later I came to a stop and engaged the 4hi, and it felt fine.

Today, I was doing <35mph, turned on the 4hi. It felt fine, but once when I accelerated it felt like it was fighting itself again. I let up, accelerated again and it did great.

Finally, my ABS doesn't work. Not too worried as it has great brakes, but the fuse it fine, so not sure what to check?

Thanks in advance.

EDIT: Someone pointed out that my rear transfer case output seal seemed to be bad. Not horrible, but said I should replace it. Already have it coming - but could that be my problem?

 

[SunlitComet]

start by making sure you have autotrac2 fluid in the tcase and shake you front driveshaft for looseness. and how does the abs not work?