Bcoots45

I got a 05 F150 STX 4x4. I just recently had the trans rebuilt and 4:56 gears installed front and rear. Its got a 6 inch lift and brand new 35s. Lately i have been getting a very noticable vibration but only when the trucks cold like 40s or below. It usuallly only does it the first time you drive it for the day or if cold out it will do it everytime. The whole truck vibrates like in a message chair. Usually starts around 35 and used to stop at 45 but lately gotten worse and does it for a bit. If i let the truck warm ip 15 mins before leaving it doesnt do it. If its 50s or above doesnt do it. I notice when it starts if u shift to 4hi it goes away but back in 2wd it comes comes back. Then just stops like a flip of a swiych. Taken to trans guy several je said he doesnt know amd didnt cause it. Any suggestions?

Bcoots45

Anybody?

PerryB

I would look at the front hubs ( IWE's actually) and vacuum system that operates them. You may have one side thats engaging due to a loss of vac. issue. Engaged is the default position.

Bcoots45

Would that cause it to only do it once a day or only when cold?

Bcoots45

Also would bad wheel bearing maybe cause it?

PerryB

I'm basing my assumption on the vibration going away in 4wd. It certainly could be a wheel bearing.

Bcoots45

ive taken it back to trans guy several times and he stated my passenger one is bad but what didnt make sense to him was it going away after warm a bearing would do it all the time. Could he of messed anything up installing gears?

Bcoots45

also is there a way to see if engaged? Or do the CVs and driveshaft turn constantly even in 2wd

PerryB

In 2wd engine running, you should be able to reach in and turn the half-shafts. Check it in "PARK" with the E-brake set. I'm thinking you're going to find one engaged.

Bcoots45

do you mean the CV axles? Just verifying. Also my 4x4 is a stick mot electronic if that makes a difference