loose drive pinion

[lakevillemn]

I recently bought a 88 F150 4X4 to use around home for hauling lumber, etc. When I bought it the front drive shaft was disconnected and the guy I bought the truck from said the 4WD worked, it just needed new ujoints. I installed new ujoints, but noticed that the front ujoint connection to the flange on the end of the drive pinion is loose (moves back and forth, and side to side). Does anyone know off hand what would cause this to be loose? Is it a big job to get this repaired? I'm okay doing many repairs on a vehicle, but I've never tried to do anything as involved as tearing apart a front axel (if that's what needs to be done). Any help would be appreciated.

 

[Cartel]

Hi there, I am working on my friends 89 ranger.
He was telling me about some vibrations and I checked the rear pinion and it moves back and forth like what you said.
I replaced the clutch not long ago and I figured maybe give the driveshaft yoke a 180 but it's obviously the bearings or a loose pinion nut.
If we are both lucky it will be a loose nut but I think it maybe the bearings are shot, and thats a major job pulling driveshafts and such, espeacially the front, omg.
If I find tightening the nut helps, I'll let ya know.

 

[FESuperDuty]

Disconnect the driveshaft from the front differential, then raise the front tires off the ground and support the vehicle with blocks or jack stands. You have to be able to roll the front wheels by hand. Get under your truck and turn the pinion yoke by hand. It should turn smoothly, even if the nut is loose. If you feel ANY grinding, your bearings are shot. This may have caused some other damage internally.