The grinding starts at around 25mph and gets worse with speed but its only in 4wd, there's no noise in 2wd at all. The 4wd works great otherwise but with such a bad noise something has to be screwed up. Where should I start?

 

The 4wd system has been covered quite a bit on this forum and there is a ton of information available. With that being said Im about to tackle this exact same problem with my 98' three button 4wd. Im starting with all the vacuum lines first then vacuum switch on top of the t-case.

Hope it helps.

 

Thanks I guess I should look at the stickies first lol, if I can't find anything specific I'll be back to this thread.

 

I had the same issue in my truck, though the speed was irrelevant. Slow or fast it made the noise. I went after the vacuum lines, actuator and such first but the front end wasn't the cause of the noise. Turns out the noise was being caused by the CV joint where the front drive shaft attaches to the front output shaft on the transfer case. I found the rubber seal cracked almost all the way around and when I turned it by hand water ran out from the crack in the seal.

When I took it apart to replace it I even found gravel inside the joint. THIS is the joint needed. You could easily still have problems with the vacuum lines and the actuator. I replaced all the lines on my truck because they were in terrible shape. While you're at it though I think it would be worthwhile to check the joint and make certain the rubber seal is still in tact. If it's not in tact then even if it's not the source of your noise it's going to need replaced sooner or later.

 

I'll be checking out the cv, theres grease flung everywhere under the front end. I'm not really into chasing vacuum problems, I don't have any of the 4wd nightmares these things can have and it's just a winter beater I'm not looking to get too involved, at least until spring.