M GO BLUE

Hello all! This is my first post after joining this forum, and I would like some technical opinions on an issue I'm having:

My ride is a 2002 F150 FX4 4x4 with a 9.75" rear end...Has 168K miles, and the truck has been taken care of pretty well and is in good condition, but doubt that rear end service has been performed in quite some time.

Recently, I noticed my right side rear axle seal had a minor leak and the left side showed evidence of weeping as well. I went ahead and purchased new seals (wanted timken, but had to settle for duralast). I pulled everything apart and replaced the seals, looked at the axle shafts, looked at the bearings, inspected/cleaned the vent and reassembled the whole deal. I measured the correct amount of synthetic 75-140 and added the correct amount of FM (which all together, seemed to overfill a bit as I had a rough time getting it all into the diff).

I drove the truck for 2 days and got back under it to check things out and found that BOTH side appear to be leaking SEVERELY now, as I see diff fluid coating the insides of the wheels/tires...

Any ideas as to what could have caused this??? Any opinions/advice would be appreciated!!!!

Feathermerchant

I'd speculate the diff is over filled. When you eyeball the volume of fluid that came out vs what went back in, more/less? Other than that, it could be the seals (doubtful) or the install (doubtful). I think typical fill level is about 1/2 to 2/3 of the pumpkin, right?

Carcrazygts2

Junk seals, along with bearing that have some play in them. Its common in the 9.75. FYI rear wheel bearing are scheduled maintaince around 100k. My grandfather truck had the same issue around 155k-160k. Same exact issue ended up being bearings.

MCpllabelle

Yup. Happened to me. Had to replace bearings.

M GO BLUE

I really appreciate all the feedback guys! Guess I'll plan on purchasing the bearings and some new TIMKEN seals and doing this job again!

I will be purchasing some new tools (which I love to do) to get the old bearings out, and would like to know what you guys recommend? I'm thinking of a 3-jaw slide hammer???

Thanks again,
M

M GO BLUE

Wanted to give everyone an update:

I bought a new 3-jaw slide hammer and beat my brains out removing the old bearing sets...both ended up coming out in pieces but got them out in about 60 minutes. I froze the new bearing sets (Timken) overnight and reinstalled the following morning....both seated back into the housing successfully and quickly using the old bearings as pre-sets. Put new (Timken) seals in afterwards...Drove it for a hundred miles, then noticed my pinion seal started leaking!?!? Not sure what may have caused this???

I Replaced it (with Timken seal) last weekend with instruction from previous posts on this site, and have put 200 miles on it since...All looks well, sounds well, and feels well! No more leaks and everything appears to be good.

Wanted to thank you guys again for the advice!!! This site is a true asset!!!

Thanks,
Matt

Carcrazygts2

No problem. Be prepared to do bearing again in about 50k. I dont know what it is, but the 9.75" loves to eat up bearings. I have since done my grandfathers again, along with mine. This time I ponied up and used motorcraft bearings and seals.. Shooting for 100k this time.