Leaking pinion seal...again?

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deeter16317

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OK, seems I have a mechanical issue, as this is too often. This is the 11.50AAM used in both the dodge and GM trucks (mine is in a dodge 2500).

With around 153k on the truck, I assumed the first seal was worn out. When the second seal leaked 7k miles later, I assumed a faulty seal. Now the third is leaking 4k later, I'm assuming I have other issues...

The place that replaced the seal both times indicated there was no obvious cause for the leak...all the seals looked good, all the sealing surfaces looked good.

The pinion flange is sleeved, and that is the wearing surface. I was told this surface looked fine. I'm thinking of replacing the pinion flange (at $200) as a last ditch effort to cure the leak. The pinion is tight, I get no odd noises or vibrations...so I assume it is still fine.

The fluid is RP 85w140, that I've been using for over 80k now (about 40k on this fill)...and I have a deep cover, holds 9 quarts of oil to the fill.

Any ideas?
 
Originally Posted By: onion
Maybe the vent is plugged?


Knew what Onion was gonna say long before I scrolled down! That'd be my first guess also.

If it has a "shaft saver"(or similar) sleeve on yoke, it's probably better than a new one.

Bob
 
Check the shaft grinding marks. They may lead in (spiral) the wrong direction. Maybe you need to change mechanics.
 
Vent is open, it was the first thing I checked when the second seal failed...

Pinion preload appears fine, there is no indication of play in the pinion shaft. No indications of a vibration either (with 4.10 rears, this thing is screaming). If the pinion was loose, the bearings would be toast by now (I have past experience with this).

The sleeve is a factory thing, it is the "wear surface" and dust shield. It could be a wear issue with the sleeve at 150k...my next step is to replace the pinion flange.

I'm thinking its got a scratch or nick that has been missed. I currently plan to fill the diff with oil and drive it home (2600 miles). With my ORU cover, I have nearly 9 quarts of capacity, so I have some buffer.
 
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This is a very old drivetrain (only thing they do) shop doing the install, I would hope they know what they are doing.

I'm going to see if I have any better luck.
 
Vent first.
Slop in the pinion bearing is the next. If it wobbles, then oil will leak. The seal surface on the flange must be in great shape. If the pinion nut is not tightened down properly after the seal is replaced, it will wobble, also. You can't just air gun it on there, as it can be too tight and crush a preload spacer too much.
Bad U-Joints can cause a leak from vibration.
 
How bad is it leaking? Are we talking about just some seepage... or is it slinging oil around?

Here's a low-tech dirty trick that I've used a few times in situations where a perfectly good seal and surface still leaks (whether due to a loose shaft, or -as in your case- for no obvious reason).

You know that little spring that squeezes the rubber lip around the shaft? On most seals, it's easy enough to remove the spring and "unscrew" it where it joins together. Cut out about 3/16", "screw" the spring back together and stretch it over the lip. Now you've got a slightly tighter seal.

I know that this is all wrong for a variety of reasons, but I've fixed a few persistant leaks this way.
 
Another low tech trick is to use a strip of 80ish grit emery cloth and hold tightly around sealing area with thumb and forefinger. "Wobble" sandpaper hand while turning back and forth with other hand. Your'e attempting to give it a crosshatch sanding pattern that'll help new seal seat. No worry of too much sanding as long as you do all you can stand in one sitting.

Bob
 
Bob, seals don't "seat" in the conventional sense.

You don't want the shaft to be too rough or too smooth. Too rough can lead to premature wear of the seal. Too smooth and there won't be enough pockets to hold lubricant. The seal lip will be starved of lubricant leading to excessive wear and stick-slip.

Surface texture requirements on a shaft that is sealed is 0.20 to 0.43 microns (Ra). This roughly translates to preparation with grit paper finer than 3000 grit.

Machine lead-in requirements are less than 0 ± 0.05 degrees. This is the spiraling of the grinding marks I was talking about earlier. Otherwise rotation can pump out the fluid.

I took a course on sealing system technology last fall.
 
Originally Posted By: mechtech2
Vent first.
Slop in the pinion bearing is the next. If it wobbles, then oil will leak. The seal surface on the flange must be in great shape. If the pinion nut is not tightened down properly after the seal is replaced, it will wobble, also. You can't just air gun it on there, as it can be too tight and crush a preload spacer too much.
Bad U-Joints can cause a leak from vibration.


Vent is OK...

Pinion is tight (or I'd have vibrations in this truck).

Not sure how the pinion was tightened, but again, the guy does it often.

Ujoints are good...
 
Originally Posted By: Kestas


You don't want the shaft to be too too smooth.




Considering this shaft has 165k on it...it might be polished smooth.

I always rough older surfaces with crocus cloth, just to ensure no burrs.
 
One other thought on the pinion being loose...if it was loose (and moving), the bearings would have stress cracked and self destructed by now...I know this for fact as I had it happen before.
 
onion - You are a good man to have around when the shooting starts!
That could be a useful tip!
[]Just bring your sawdust for when the gears start making noise!]
 
Have all three seals since the switch to Royal Purple? If so consider trying some dino gear lube and some auto-rx. What do you have to lose. If it doesnothing you are not out much at all.
 
I have over 90k with RP, and 40k of that running with the pinion submerged (the fill on the ORU cover is around 1" higher than the OE cover).

The shop owner made comment that synthetics are more "solvent" than dino, but this truck calls for synthetic from OE.
 
Originally Posted By: mechtech2

[]Just bring your sawdust for when the gears start making noise!]


I talked to an Australian mechanic once who reccomended the use of a bananna for such applications.

Originally Posted By: deeter16317
I have over 90k with RP, and 40k of that running with the pinion submerged (the fill on the ORU cover is around 1" higher than the OE cover).


I think we've just identified the problem.
 
Originally Posted By: onion
I think we've just identified the problem.



What? The overfill? If that was the cause, it would do it at normal fill...think of a diff, the pinion is flooded always, and is really flooded when moving since it gets oil from the ring gear. No different than a wheel seal...and their not leaking.

I don't buy it...a 150k (40 flooded) and it starts seeping, then within 12k I replace 2 seals (one at a normal fill level)...its not the level of oil. If it was, the OE seal wouldn't have lasted 40k when the others only lasted 5k.
 
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