A U joint failure in the drive shaft usually causes a vibration at speed and a clunk as you change the trans from forward to reverse while "stationary". If you park your vehicle on a level surface and take all the load off the front driveshaft (neutral) then you will be able to see the slop in the U joint. If it is bad then you will see the damage to the seals.
Have you checked the oil level in your front differential since low oil will take out the bearings and damage the hard surfacing on the crown wheel gear faces?. Little marks (removal of metal) in the crown wheel will cause a whinning noise at highway speed. Fixing differential problems is not a "kit" replacement procedure.
While changing the pinion bearing seal can be done with the differential in the vehicle, to change the 2 taper roller pinion bearings requires the differential to be removed on the Explorer. New pinion taper roller bearings require the adjustment of the pinion gear engagement with the crown wheel so you need to measure tiny measurements to shim the pinion for correct gear pattern. The Ford procedure details replacement of pinion bearings and differential carrier bearings and the measurement and shimming of the new clearances. There are several special tools that Ford says are required. I have the procedures for axle removal and the replacement of the 3 bearings and correct matching of pinion gear depth with crown wheel gear. PM me if you want the procedures in pdf format.
I did the 3 bearings on my son's 3/4 ton GM truck front differential and it was a far simpler job than on the Explorer.
Good luck.
Sure would like to see that pdf on the details to rebuild the differential. I can do it myself easily...have already replaced the axle shafts, ball joints, control arm bushings, shocks, sway bar bushings, and wheel bearings. Saw a few different videos on the rebuilding process but no specs. The special tools list would also be a bonus, I know a couple of different places where I should be able to either borrow or rent them.
Also, I have seen rebuild kits available form a few different vendors..some kits include some things...other kits include different things, depending on what a consumer needs to replace. Is this perhaps why you mentioned fixing a differential problem is not a kit process? It sure does seem to be. Of course...without taking the whole thing apart it is impossible to know what needs to be replaced. My 2004 ST has 339,000 km on it (203,400 miles) so I am going to make the assumption that everything inside that can be replaced needs to be or should be replaced anyway once it is all apart.
Having said that....does anyone know of the most complete differential rebuild kit available? I am assuming the crown and pinion gear are okay...but not necessarily. When I grab the prop shaft and 4WD is off with vehicle parked and in Park ...I can spin the prop shaft quite a bit in either direction...very loose. Not sure if this huge backlash would be caused just by a worn out pinion gear bearing. Also the new axle shafts have about 1/4 inch to 3/8 of inward and outward travel into the differential where the snap ring is supposed to hold it in place. The snap ring locked into place when I installed the new axle shafts...but they still move in and out way too much....I think.
Maybe time to just go get a used on from the wrecker? Any comments would be appreciated. I figure rebuilding the existing would cost about the same as a used one from a wrecker and I am leaning towards doing the rebuild so I know I am not putting back in a worn out POS from the wrecker.
Thanks in advance from the Great White North.
Mark
