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Rear Pinion Seal Leak

26K views 22 replies 13 participants last post by  me2 
#1 ·
I have a minor leak from my rear pinion seal. Replace or just keep an eye on it? How do you replace this thing and how hard is it?
 
#2 ·
Is it a leak or a seep. Is any fluid dripping. If it is only a seep, I would not touch it.
 
#3 ·
It is a seep, and a minor one. There is never any oil on the floor, I just see it on the bottom of the diff housing. I've been watching it for about 8 months and checked the fluid (Amsoil) twice; full both times.
 
#6 ·
It is a seep, and a minor one. There is never any oil on the floor, I just see it on the bottom of the diff housing. I've been watching it for about 8 months and checked the fluid (Amsoil) twice; full both times.

Mine was doing this same thing and one day I got to the destination of a 650+mile drive and my spare tire and fuel tank were splattered from fluid being flung off the U joints.

My buddie Marc and I changed the seal out at the last LCD dyno day in 30 minutes. The hard part would be the special tool needed to get the yoke off the pinion. Barely got any fluid on the ground it went in so easy and fast.
 
#7 ·
Thanks for the advice. I will probably just monitor it.

When I do have to replace it, how hard is it? This can be done without going into the differential, right? What special tools are required?

Thanks
 
#8 ·
I know on the Dana 80 it takes a thin wall 1 7/8 socket I believe and the only place I can find one is from Snap-on for $80. A friend of mine took a reg. 17/8 socket to a machinist and got him to thin it out for him for $40.
 
#9 ·
This is becoming more of a problem.

Anyone got a writeup on the proper way to re-install and torque the yoke?

Thanks
 
#10 ·
Just drop the driveline, the hard part would be the special tool needed to get the yoke off the pinion. Barely got any fluid on the ground it went in so easy and fast. It took my buddy and I, he a is Ford Diesel Tech, 30 minutes. I did most of the watching, he did most of the work.
 
#12 ·
Check the vent tube that runs from the top of the diff housing to the frame rail, and the little plastic fitting on the top. Any obstructions in it will create a pressure difference between inside the diff and atmospheric pressure and can cause the seal to leak
 
#13 ·
Dont ferget about preloading the pinion!


If you pull it apart theres a crush sleeve that will need replacing on the pinion shaft... It sets the gear mesh... its excatly what it sounds like, it gets crushed when the nut gets torqued. ....Get it wrong and your gear will start uneven wear .... then you will be shooting gears thru the diff!

things to expect...
You gotta tighnen the nut untill it takes (8-14ft/lb? cant remeber the number anymore) to turn the carrier with the axle shafts out.

-check the pinion bearing by removing the axle shafts, then grabbing the pinion and turning it with your hand. It should spin equally freely all the way around. any bit of resistance in any areas indicates a bad pinion bearing which would need replacing.... that requires removing the whole carrier... new can of worms.
Also your "suppose" to get a new pinion nut too.

But hey some people get luckly by blasting the nut on and call it a day.


Id just leave it, pritty common problem as long as its not pissing out oil it should be good- but will need to be replaced evenchually to save the pinion bearing.
 
#14 ·
Preload on a new crush washer is 35 ft lbs & on a used one I believe it's 25 ft lbs. Main thing is when you tighten it back down go slow. Pull on the yoke & check for in & out play. You want no in & out play but you still want to be able to spin the tires with one hand freely. Jack the rear up & put the axle on jack stands then use a pipe wrench & a 6x6 block (or what ever you have laying around) to brace the wrench. Clean the threads & apply locktite. just go slow & TAKE YOUR TIME.

A 2 jaw puller will work just fineleave the nut on there alittle ways to help center it & hook on the back side of the yoke.
 
#15 ·
Hopefully, the new seal will take care of it. But, my seal was replaced at around 50k miles (along with new inner and outer axle seals), and within a thousand or so miles, it started it's slow drip again. I had the shop that did the work put a second seal on it (supposedly an improved seal over the oem seal), but it started leaking within about 5k miles. I took it back a third time, and they could see where the pinion yoke was slightly out of round. It was a Ford-only part, so I had them just slap a new seal on it and that was 45k miles ago. I've just sort of learned to live with the annoying drop of oil every once in a while (didn't want to fork over the $250+ for the new yoke). About once a quarter, I crawl under the truck and top off the oil with Royal Purple synthetic. It usually only takes half a cup to top if off (if that much). Now, keep in mind that I don't tow like a lot of you, and the truck stays parked now except for the occasional 200 mile round trip to the lake house. I think I've driven about 4k miles in the past 12 months in it. Maybe one of these days, I'll put it on my list of things to fix.

short_stuff
 
#16 ·
If it is the Dana 80 you do not have to worry about the preload, pull the nut off and tighten it back to spec.
 
#18 ·
Thanks for all the advice. First thing I am going to check is the vent. Then see how much fluid I have lost before deciding my next step.

I think I have the Ford 10.5"; can anyone verify that? It is a 2000 F350 SRW.

Seems like the best procedure I have found (short of tearing into the diff) is to measure the turning resistance with a beam torque wrench & mark the nut and yoke before removal. Upon reassembly, get the nut back to it's original location while checking the truning resistance to get it the same.

I've done this before on a jeep and it worked ok. Sounds like a pain though; jacking it up to measure the resistance, lowering it to tighten a bit, repeat, repeat, repeat. Anyone got a better idea for holding the yoke so it can be tightened?

Thanks
 
#19 ·
If she is a single rear wheel its the 10.5 . Duallys are the D80s

You got the procedure of doing it right down.

You may find it easyer to unbolt the axle shafts and pull them out like 1 foot. Doing this makes it so you dont have to jack up the truck when you measure the resistance. You can pull the axle shafts out of the axle with out pulling a wheel off. Just undo the 8 (5/8"?) bolts on the hub the pull it out, that easy.

And be sure to tighten those bolts when done, and recheck...... I didnt, I sheared all 8 clean off and had a hell of a time getting the rest of the bolts out.
 
#20 ·
Thanks!

Anyone got a good method for holding the yoke while taking the nut off? It has to be torqued pretty high.
 
#22 ·
A ten dollar puller from Oreillys will work. I made my own since I was too lazy to go to Oreillys...

Drop the rear of the drive shaft, four bolts. Remove the pinion nut, use the puller to remove the yoke. Remove seal, and reinstall new one. Takes longer to drive to the store for parts than it does to fix.
 
#23 ·
The pinion seal on my '99 always leaked. When it was new, I took it to the dealer twice to get fixed. One time the fluid level got too low and it took out the pinion bearing. The dealer put a new one in.

Since then, I put in one pinion seal myself, only to have it leak too.

I got fed up with the leaking and started asking questions. People told me it could only be one of two things. Either the oil was getting too hot burning out the seal or the oil level was too low and the seal was running dry. Either one will wreck the seal.

So... I got myself one of the fancy new aluminum finned diff covers from an 08 rear differential. Then I removed about an inch of a fin near the top of the cover and drilled and tapped a 1/2" fine threaded hole in it, to fit a #8 ORB plug.

I put in a new pinion seal and then overfilled the differential by a few pints using the new fill plug on the diff cover.

The new seal hasn't leaked a single drop since then. So either it was running dry or it was overheating. In any event, my leaking pinion seal problem has been solved.
 
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