jimmy front end noise

I have a 1998 GMC Jimmy SLT with 95,000 miles. Every now and then there is a noise coming from the front end passenger side like were rolling over the rumble strips, it only happens when we drive it seems on the expressway, when this happens I will pull over stop and take off again and it quits also while the truck was making this noise I put it in nuetral and the noise continues if that means anything... I cant duplicate the noise for my mechanic its been in three times already...
tie rod and wheel bearing relaced on drivers side already can any body help! Does it sound like a front end problem or transmission problem.
THANKS

If it is a 4x4 I heard that there is a plug on the front end that sometimes goes bad. The only bad thing is I don't rember where the plug is. Maybe it will show in the Chilton. Does it sound like the 4x4 is trying to engage?

It does sound like something is trying to engage, I do have a manual and I will try to find this plug you suggested.

It does sound like something is trying to engage, I do have a manual and I will try to find this plug you suggested.

Check the vacume diaphram under the battery tray. Mine did the same thing. It drove me nuts. Also check all of the vacume lines in the area. Good luck.

I will give that a try, Thanks

What kind of noise is it?

I have a 99 jimmy and I had the same problem and I replaced shocks, ball joints and still no fix and finally I figured it out. Believe it or not it was the rubber cushions under the hood and the rubber seal under back of hood. One ruber was missing and the back seal was crimped so the hood was bouncing against metal from time to time making an awful clunking noise. I fixed that and problem no longer existed. Check it out it could be an easy fix.