Not sure how much I can help, although others here may.

Are talking about when your turning or straight or both?

What speeds do you engage it?

Are you in "high" or "low"

I have a 98, I don't know if a vacuum loss will affect this for anything other than engaging or disengaging, but the two vacuum lines at the front wheel corrode and allow a leak. A slight lurch is maybe normal, but i couldn't engage/disenge. I hope this may help.

Answered by Service Writer (expert)
9,955 answers provided

I've never really had it in 4 low. The problem is in high at any speed. Flat ground as well as hills. Corners or straight stretches, it doesn't matter. That is my concern. I have had it happen on hills, and had my rear end bust loose. If that happened on a corner, it would be a real problem. I guess the best way I can describe it is doing 55, it will give a big lurch (like a big tug) like something is kicking your truck in the butt. No real noise though. Hope that helps. Thanks.
Ps. I'm new to this site, and not sure about the whole donation thing. But, I'd be happy to do it.

Response from wiseonep
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There is a link next to the reply button that says small donation if you are so inclined :D

There are certain speeds that you want to engege the 4-wd and speed you don't want to. Don't do it under 10 mph or over 50. It can't engage accuratley and it will slam in or slam out.

A weak vacuum will cause a partial engagement and slam. There is a vacuum line the goes to the wheel, follow it back to where it connects to a metal tube. Disconnect and clean this tube with enery cloth, and try to clean the vacuum line if anything crusty is in there with a pipe cleaner or whatever you think of. LIGHTLY apply a small amount of silicone around the metal tube no closer than 1/4 " from the end, and reattach the vacuum line. This is where mine had a problem.

If problem is still happening, check the vacuum of the system for leakage.

Answered by Service Writer (expert)
9,955 answers provided