Can anyone tell me the size of the pinion nut on the front third member? Anyone ever had to change the front pinion seal? I've got a some mobil 1 synthetic 75w-90w gear lube that I need to find a use for, can I use it in the front diff. Thanks

 

bump...id like to know this as well, got a leaking seal, topped off the front diff and soon found out why it wasnt at the proper level.

 

I'm not sure about the nut size, but I know that there is a fill plug on the front differential, but no drain plug. So to drain then fill it, you have to use a suction pump or something to pump the oil out, and then to pump it back in.

 

Just changed mine and used a 1 1/4" socket on an impact wrench. Had to brace the yoke with a large chunk of steel so I could loosen the nut, it was on tight. Put marks on the drive shaft, yoke and univ. joint. Noted the marks on the pinion nut and top of threaded bolt in the center and number of threads showing.Took a small flat screw driver and hammer and was able to get the old seal off the housing. Used a larger flat blade and was able to work my way around the whole seal and gradually worked it right out. Checked the area where the seal sat for burs and dirt. Installed the new seal by placing on by hand and gently tapping all around evenly with a hammer. Went in good. Got the yoke on OK but when I went to retourque the nut could not apply enough torque with the rachet to match the marks on the nut. Ended up about 1/4 of a turn short of the original marks. Make sure the universal joint goes back to gether right, cups inside the small metal blocks. Bolt it up and reinstall the diff fluid that I forgot to mention to drain at the start. Didn't have any driveability problems but noticed the leak is back. On closer inspection it doesn't appear to be coming from the seal but from between the housing and the metal part of the seal. Not sure what to do now except keep checking levels and hope it doesn't run dry. There must be a flaw on the housing itself.
Good luck

 

Needles to say I still haven't changed my front diff fluid in my truck. Still wondering what kinda fluid to add to the front carrier. 93 Olds Bravada AWD. Thanks

 

i just use 80w90 hypoid oil from walmart. turned out my seal was a axleshaft seal, not the pinion. a year and a few months later did the passenger side axleshaft seal, pinion seal is still the original, and for now not leaking.