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Oil leaking from pinion seal after driving.

9K views 19 replies 9 participants last post by  Ivy66GT 
#1 ·
Hi all,
I would just like to pick your brains with an ongoing issue that I have.

A while back I replaced a leaking diff pinion seal and all was good. I tightened the pinion nut to the position it was in before removal by counting the turns.

Now I find that when I return from a longish drive, I find oil covering the underside of the body, the diff bumper and the shocks.
Obviously coming from the rotating pinion shaft.
The seal does not drip from the bottom of the diff.

If I tighten the pinion nut to put more pressure on the crush washer, do you think it will stop this residual leak?
Or is the seal a bad one.
 
#3 ·
Tightening the nut will not add pressure to the seal in the same way that one might tighten a gasket. The seal rides against the pinion flange, and sometimes replacing this seal is not enough to stop a leak. The seal can often wear a slight groove in the pinion flange. A thin repair sleeve can be pressed onto the flange to provide a fresh sealing surface, but some owners prefer to replace the flange altogether.

How old are your bearings? If the pinion is wallowing around, it can exacerbate the problem.
 
#6 ·
The bearing seemed OK at the time.
I can't recall seeing a bad groove in the pinion shaft but there was wear.
I'll have to take it out and have a closer look.

Are the repair sleeves available at parts shops?
 
#5 ·
I agree with Urambo. Only you have seen the shaft to know if it had a groove worn into it.

I have been successful changing pinion seals without a new crush washer but in addition to counting turns I always try to make sure there is some tension on the nut before I stop. That means probably turning the nut a slight bit beyond its original position. Not trying to add more crush necessarily but making sure there isn't any free play. That isn't the 'official' way to do it but its not an unusual method either since it involves a lot less work.

If the nut is not tight enough then the bearings can allow the shaft to move around, as would bad bearings, and ruin the seal causing it to again leak. The movement beats up the seal so that its center hole is too big to seal anything. Not tight enough can also ruin the bearings eventually.

I agree that tightening the nut itself won't directly make any difference in whether or not the seal leaks. But if the problem is a loose pinion assembly then more tightening might help. Its not going to make it worse so you might as well give it a try.
 
#10 ·
most likely vent or v hose or both clogged,but.

you should disassemble the pinion again and do over using the correct parts and torque. replace the crush sleeve, check manual for correct torque some are around 450 ft lbs, don't know on yours. you need special holder wrench for pinion flange and torque wrench. if the job is worth doing it's worth doing right. do it right the first time instead of doing over
 
#11 ·
The trick to replacing the crush washer is not the final torque on the main nut, but the running torque as the crush washer puts more friction on the pinion bearings. This can only be set with the pinion removed and a special very low bar torque wrench. This is one reason most people do not try to do this the correct way.
 
#13 ·
Pull the driveshaft out and see if the oil is originating from under the pinion nut, it will be easy to figure out as you will see oil broadcast from that location. The nut did have a thread sealant when new and upon removal and reinstallation is more than likely gone. I have replaced the pinion seal before with good success and not changed the crush washer by finding the torque required to move the pinion nut starting at 50ft. lbs and trying to tighten the nut. It usually sits at 85-90ft.lbs and as posted above a new washer requiers as much as 450 ft. lbs to begin the new crush washer to collapse but when it does, 90 ft. lbs moves it. New bearings will need to be set at 25 Inch lbs to begin rotation of the center section with axles removed and used bearings 15-18 Inch lbs. This can be tricky and is a "feel" type thing too becase a new lubricated seal adds rotational resisitance too.
I believe if your pinion does not have a worn groove in it that it needs tightening and sealant under the pinion nut. Take off the nut, pull the yoke and if its smooth ( it will have minor wear line - they all will unless new) clean everything with degreaser, replace the seal one more time, apply sealant under nut flange and threads, set the parking brake and torque to 85 ft. lbs and you should be good. My $.02
 
#14 ·
Ok I got the car on the hoist and had a look at all that was suggested.
Firstly I removed the breather, all clear.
Then I removed the nut that screws into the diff, all clear.

I removed the tailshaft and the yoke. The yoke have a very minor groove only just noticeable when scraping a fingernail on it.

The oil was leaking from the spline of the diff and pinion nut. (inside the yoke)
Cleaned the yoke and pinion nut.
Reassembled and added RTV silicone between them both (I had the RTV silicone on there before) and tightened the buggery out of it, about a one quarter turn more than it was before.

So when I take it for a run on Sunday, I will report back and see if the silicone worked.
 

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#15 ·
You may just not have originally had the nut tight enough allowing the spline to move slightly and allow oil to leak past. That was the case with one I re-did many years ago before I owned an in-lb torque wrench. Re-reading my notes that one sounds exactly like your current experience.

As the rear axle wears the turning torque goes way down. A big part of the initial in-lb spec is anticipating that the bearings will loosen up with use. The small torque is supposed to be measured without axles or anything else but that means much disassembly. The last one I did only had 5 in-lb when I took it apart and that included the extra torque from turning one rear axle/wheel/seal. It took about 80 ft-lb on the nut to make it 10 in-lb when I reassembled it and its never leaked since. The nut was obviously beyond the mark for its original position but I didn't record how much beyond since I was measuring torque.

The Ford spec for an 8" axle says 17-27 in-lb with new bearings and only 6-12 for used. It doesn't take much nut torque to reset one to 6 in-lb. That is good, since underneath the car without a lift you can't usually get much torque on the nut.
 
#16 · (Edited)
When I rebuilt my 8.8 with new bearings, I tightened the pinion down to 25 in-lb of rotational resistance. After that, I continued to install the carrier and axle-shafts. Out of curiosity, I checked the pinion again with my torque wrench, and found that even with the other components attached, there was absolutely no increase in resistance. Despite the weight of the carrier and axle-shafts, new bearings and oil kept it all turning freely. I was impressed.
 
#19 ·
Took it out for a good run today.
Got it back and up on the hoist and there is no oil evident or that has sprayed about the underside.
A little bit of residual oil under the diff that was caught up behind the seal when the pinion was out.

So yes the sealant did do the trick but I am wondering for how long.
Does anybody know what sealant was used from factory?

Another plus is that since tightening up the pinion nut, it has removed a slight clunk I used to get a bit sloppy changing gears.
 
#20 ·
I am pretty sure it would have originally been what we call Permatex #2. I don't know if that is available down under. Its a thick, black goo in a 1-2 ounce tube that is officially 'non-hardening' although after 40 years it will turn pretty dry and hard.

If the nut is tight enough that the yoke won't move then I wouldn't worry about it leaking for a while.
 
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