Rear differential leaking
Thread Starter
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Senior User
Joined: Aug 2005
Posts: 183
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Rear differential leaking
Just got the truck back on the road again, parked it last night, come out this morning and the rear differential is leakin bad, almost pouring out gear oil. Its coming from the front where the driveshaft connects. I believe its called the pinion shaft, so therefore it would be the pinion seal that is leaking? What i need to now really is if I can drop the driveshaft, unbolt the part that connects the ujoint to the differntial, pull it out and just replace the seal. If i was at home and had access to my garage and all the tools I would pull the whole rear axle and go through it, but im at college, only have some of my tools and cannot really tear the truck way down. Any questions, comments, corrections are appreciated. Thanks
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
More than likely your pinion nut has backed off and is allowing the seal to leak.
The correct way to do it is to remove the wheels and drums. Drop the driveline, and remove the nut and crush sleeve. Put a new crush sleeve in, and find/make something to hold the pinion in place. Torque it down until there is 8 in-lbs of drag in the pinion bearing. This usually takes somewhere in the neighborhood of 300 to 400 lb-ft. If you crush it too far, you need a new crush sleeve and have to start over.
However, I had my truck in the shop a few months ago and had the same problem. He only charged me for parts, not labor. So I'm guessing that he just torqued it down and said good enough. It's been fine for about a year now.
Oh, this is for the 8.8" axle - can't speak for the 9", sorry. Hope this helps you.
The correct way to do it is to remove the wheels and drums. Drop the driveline, and remove the nut and crush sleeve. Put a new crush sleeve in, and find/make something to hold the pinion in place. Torque it down until there is 8 in-lbs of drag in the pinion bearing. This usually takes somewhere in the neighborhood of 300 to 400 lb-ft. If you crush it too far, you need a new crush sleeve and have to start over.
However, I had my truck in the shop a few months ago and had the same problem. He only charged me for parts, not labor. So I'm guessing that he just torqued it down and said good enough. It's been fine for about a year now.
Oh, this is for the 8.8" axle - can't speak for the 9", sorry. Hope this helps you.
Elder User
Joined: Dec 2002
Posts: 550
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From: Effingham,IL USA
i would check the pinion bearing to c if it is loose first. a lot of times the bearing wears out and gets play in it and that play tears up the seal. so if u replace the seal and the bearing is still "loose" itll do the same thing to the new seal. i always put the truck in neutral and let it roll itself to a stop then chock the wheels when checking the pinion bearings. that way you dont have the park pawl or trans putting strain on the driveshaft, which probably will not let you feel the loose bearing if it has one. grab the back of the driveshaft and try to make it move to c if the bearing is tight.if the bearing is still good changing the seal shouldnt be a really big deal as long as you have a good impact gun and mark the nut b4 u take it off. then tighten the nut to match the mark u made so its about the same torque as b4.
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Senior User
Joined: Aug 2005
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I should have included this before, the truck is an 86 f150 4 sp np-435 with the 8.8 rear end. When i grab the end of the driveshaft there is play in the pinion, but the nut itself is not moving, so is it possible that the nut is just lose or definetly a bearing. Next problem, unfortunately i am 4 hours away from home where i have all my tools including my air compressor and impact gun(s). If i were to leave the rear wheels on the ground just to break the nut lose or tighten it up so the whole differential assembly does not move, would that be alright to do or am i gonna get myself in to more trouble doing that. Thanks for the quick responses.
Cargo Master
Joined: May 2001
Posts: 3,208
Likes: 13
Drop the drive shaft set the parking park and see if you can get the nut loose. If the nut was loose then replace the seal and and tighten the nut it takes a pretty good pull to crush the sleeve I usually have to put a cheater on my breaker bar to get it to crush so if you don't get to crazy about it you be ok. If the nut is not loose and the rear end wasn't noisey then do same thing just replace the seal. If the rearend was noisey then you probably have a bearing problem and will have to replace the bearing and race and that unfortunately means the rear end should be setup again with a new crush sleeve and shims. PS If you have trouble holding the yoke see if you can borrow or rent a pipe wrench put it over the yoke so that when you try to take the nut off the wrench handle comes up against the frame.
