4x4 vibe ????

My tuck is having a front left vibration at 40-50 mph in 4wheel only. As soon as I turn the back to 2high it goes away. 2nd gen 6inch lift. With drop kit. I’m thinking it’s the needle bearing. But all the treads I read are saying symptoms are the opposite. The vibe is in 2 high and goes away when you put in 4h it disappears. CV’s look good. No play in the axle. Don’t want to spend time an money in replacing the needle bearing with the ecgs bushing it it’s not the problem.
Let me know guys.

 

If it is safe to be driving over about 25-30 mph being in 4X4 is more of a handicap than a help. This isn't an AWD vehicle. Sounds like you're driving on pavement in 4X4. If so you're wearing out drive line components prematurely.

 

Just out of curiosity why are you driving 50mph in 4WD??? I’m thinking if it doesn’t do it in 2WD and only in 4WD at 40 to 50 MPH it’s not a big problem and I wouldn’t worry about it. And i generally wouldn’t drive that fast in 4WD

 

U joints are likely.

 

You can shift into 4x4 safely up to 60mph. It's in the manual. I have cruised i-90 at 70mph in 4x4, it is not an issue.
Another vote for u-joints. Gotta be something with the front driveshaft.

 

40 up the pass I drive to work. I live in Colorado. Usually 2 wheel to and fro , when it snows need 4h to get to the top. Then I switch back in 2h
U joints. Could be. I’ll check that in the morning.

 

Agreed ryfox. Obviously it’s in the front drive shaft area. I’ll be digging into u joints and maybe grease the zerks ? See if that helps

 

I would do a fluid change in the front diff. It’s easy enough, I did all 3 in about an hour a few weeks back. Check the magnet for metal and the condition of the fluid could tell you a lot. Black sparkly fluid would spell trouble.

Putting in some high end synthetic gear oil might help smooth things out. My truck was slamming in and out of 4LO so I thought I might as well do a fluid change, it was overdue anyways. Shifts like butter now.