I have been having a hard time diagnosing an annoying humm noise. It happens when I reach 20 to 30 mph and goes away after going faster or slower. If I cost down a hill going that fast, it doesn't happen. My first suspect was u joints, so I replaced them both and also found a small hole in the drivers side inner boot on the cv. So, I replaced the entire shaft. I've replaced the front and rear diff fluid and made sure the transfer case was full. Now I'm about out of ideas. Any ideas would be greatly appreciated!

 

Possible toe wear on the front tires???? Try rotating the tires front to rear.
Possible slip joint or binding universal joint on front drive shaft???? Remove the shaft & drive it.

 

+1^^^^
Sounds like the captain is right on with those ideas.

 

Thanks for the ideas guys. I kind of ruled out tires because it only happens during acceleration but I will give it a try. Also will try the slip joint. I already replaced the u joints but ill shake em down again to make sure there not binding.
My transmission was rebuilt about 3 months ago, wonder if I should have them take a look at it. I know its very hard to diagnose sounds online but thanks for tryin!

 

You're finding out it's tough to diagnose noises when you're right there, much less online! Let us know what you find.

 

Lol, very true. Ill be sure to post back!

 

Yeah having them check out the trans should be a free warranty thing to do. As for the tires if it's the front tires they get slightly lifted when you accelerate, so the toe in captain was talking about does make sense. Any uneven wear on them?
Look for posts about front end humming that are pertaining to transfer cases, axles etc. I've seen lost of recent posts about humming noises. Maybe the transfer case is partially engaging and/or fluid in the vacuum line causing it?!

 

I thought that as well about the front end engaging so I tried it in 4 wheel and it still does it. I found that if I accelerate hard threw the gears it doesn't happen but if I drive granny style (which I usually do lol) then it happens. So I'm definetly thinking something tranny related, going in next week to the tranny people.