98 4.0 L XlT 273K ,,,When I hit a bump sounds like transfer case is trying to engage grrrr 5 to 70mph I can flip 4x4 to 4hi back to 2wd and it stops, checked out all electronics changed fluid and transfer case motor, only time it doesn't do it is when it's really cold. What's up with this
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Welcome to the forum

Not sure what you mean, so a little more detail.

Does it feel like both or one of the front wheels are engaging?
1998 had PVH(pulse vacuum hubs) which did have issues.

If transfer case was engaging you shouldn't "feel" anything since front hubs would not be engaged.
The transfercase is shifted from 2WD to 4hi and 4low by an electric motor on the back of the transfercase.
There is a connector on its wiring by this motor
Unplug the connector and go for a drive, see if the problem stops or stays the same.

This would determine if 4x4 control module had internal short causing it to shift