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Rear Pinion Leak

Henre

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My vehicle is a 2000 Mercury Mountaineer AWD V-6 with a standard open rear differential with 111,000 miles. Recently, the pinion seal started to leak a bit. It appeared to be the original seal. I installed a new pinion seal. The leak stopped for 4 days. Now after about a hundred miles, differential lubricant is being thrown out in a small amount coming off the pinion flange.

The pinion flange where the seal rides appeared to be smooth upon reinstall.

I have several questions.

Is it possible I put too much fluid in the differential? The owner guide says fill to about 1/2 inch below pipe plug but I filled to overflowing.

Does the pinion nut require loctite? Can fluid get past the pinion nut?

What is the proper torque specification for the pinion nut? I do not have an inch # wrench so I measured the distance from the end of the pinion shaft to the face of the pinion nut (7/32") and duplicated that upon reinstall.

Does anyone have a blowup diagram of this gear set showing the pinion shaft and associated seals, shims and nut?

Why is the pinion flange such a tight press fit on the pinion shaft? Why is the torque on the nut so important, it doesn't seem to hold the pinion in the case? Is it possible my pinion nut is now too loose?

How is the pinion gear and shaft actually held in place in the differential?

On doing this job, I did not pull the wheels off and I did not drain the fluid completely, after the flange was pulled off I just let the fluid run out the front of the differential into a pan, pulled the seal, wiped the inside of the sealing area and put in a new seal. About a quart of fluid came out and I replaced with new fluid the same that was in the differential.

Any thoughts would be appreciated! Thanks

Henre
 


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Henre

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Does anyone have any thoughts? Please
 




RomeovilleIL

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Thoughts? Okay, here goes.

Is your fix okay? Big can of worms. Lots of people have fixed the way you described with no problems. Most guys count threads or measure as you did. It's all about the preload on the crush sleeve. For some, the retorque wasn't right and blew up the rear ends so its a crap shoot.

As for oil working out up the splines and around the nut, it does happen. It should be pretty evident if the leak is coming around the seal you installed or out through the center of the pinion. I have seen advice to put a little rtv or liquid teflon on the splines when reassembling to prevent seeping. I am fairly certain you do not want to put locktight there. Locktite on the nut is probably helpful in keeping things from loosing with use after reusing the nut, but don't think that will have an effect on seeping.

At this point what's done is done. Pulling apart again and adding a sealant to the splines is probably a good idea to get rid of the leak. Let it dry before refilling. Overfilling is not honestly possible filling from the plug unless maybe you are parked on a 60 degree incline. If the original torque wasn't reset right, a second go wont make it any worse.
 




Henre

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Thanks RomeovilleIL for the reply!

The seal appears to be holding, but the flange seems wet with fluid. I am thinking fluid is getting past flange nut.

I need to find the factory nut torque spec. Where can this be found?

I plan to watch issue for a while, and depending on developments, check torque on flange nut. Maybe use a bit of sealant on nut face. I may have been too lite on the tightening. I realize one must be careful on the reinstall.

Henre
 




Henre

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Update. After another 80 miles, pinion seems to be not leaking. Will continue to watch. As best as I can determine flange nut torque spec is 20-25 inch-pounds.

Henre
 




OneLever

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I am thinking fluid is getting past flange nut.

There is a Ford TSB concerning fluid migration past the pinion nut. I can't find the TSB number but if you search for it I'm sure you can. The solution was to apply some type of teflon sealant to the pinion nut threads I believe.

The torque for that nut is important because it determines the force on the pinion bearing. If the pinion bearing has the wrong amount of force placed on it then it will fail prematurely. Something called a crush sleeve is used to determine when the proper torque is reached.


Edit:
Here is a helpful video showing the idea behind setting the pinion nut preload: Link
Look at your driver's door sticker. What is the axle code?
 




Henre

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Thank You "OneLever" for your reply. My axle code is D4. The video was good!

At this writing the pinion seal seems to be holding, with no fluid build up on companion flange. As stated in my original post, on reinstall I just tightened the flange nut to it's original location (7/32 from end of threads to outer face of nut), but I did not use any sealant on threads. I did not install a new crush sleeve.

My plan is to watch and see if fluid appears. If so, I will pull nut and reinstall with sealant on the nut.

My axle is a standard open differential as far as I know (not a limited slip).

Henre
 




Henre

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Followup Comment

Upon removal, the old pinion seal appeared ok. The sealing surface on the companion flange was smooth.

But, upon closer exam of seal, there was a defect in the spring that acts as a collar under the rubber sealing surface. The partial break in the spring apparently caused unequal tension on the flange sealing surface allowing fluid to leak out.

Henre
 




OneLever

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My axle code is D4.

I have the same rear axle as you (D4) and it is a limited slip. If you read this write up by my pos mounty you'll see the following line "D4...….....……. L/S 8.8".…...…...... 3.73". Which I believe is what was listed in my shop manual.

I just tightened the flange nut to it's original location (7/32 from end of threads to outer face of nut)

Some guys get away with doing it that way. The idea is to get the pinion bearing preload at a sweet spot. Where the pinion can still rotate freely, but not so freely that the pinion flange can wobble around I think. Here is a video related to the first, in the sidebar on youtube you can see more from this person demonstrating preload: Link

The sealing surface on the companion flange was smooth.

Good deal.

But, upon closer exam of seal, there was a defect in the spring

That would make sense. While installing these seals it is not uncommon for the new spring to get snagged or out of place as well. So I have heard the advice given to use a little grease or Vaseline to hold the spring in place during installation.
 




Henre

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Thanks OneLever!

I double checked my door code and it is a D4 which is limited slip. The local Ford dealership where I purchased my new pinion seal told me I did not have a limited-slip (he looked at the VIN). Strange! He did sell me the proper differential fluid for a LS (75X140). Strange! I trusted the parts guy--maybe not a good idea. Rather, trust but verify!

I did lubricate the new seal lip generously with gear lube before the install of the companion flange.

The link was good. Thanks

Henre
 




OneLever

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You're welcome. Feel free to update us in a month or so.
 




imp

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A few added thoughts

Henre, having specialized in rear axles for years, I thought perhaps a few comments might be helpful to you.

The "crush sleeve" has the purpose of resisting the tightening load of the nut, until such point as correct bearing preload is attained. In racing applications, knowing the crush concept is not foolproof, a SOLID washer is used, this requiring more care in setup to secure proper preload while requiring appropriate nut tightness-- this system is much less forgiving of "mistakes". Re-use of the crush sleeve is OK, but only OK, not perfect, and with original bearings and shims in place, which you have.

Overfilling with fluid is also OK, to the extent that it will not cause seal leakage UNLESS the vent tube is clogged.

Seals tend to wear a minute groove into the pinion, sometimes hardly detectable; this can cause a new seal to leak. Sometimes, hammering the seal into place causes the garter spring to fly out of the seal, unbeknownst to the installer- a sure leaker being created. If the pinion seal surface is grooved to any degree, the seal may be installed to a greater or lesser depth, in order to secure a fresh, un-grooved surface for the seal lip.

Bearing pre-load in these types of gearsets is of UTMOST importance to quiet long-life gearing. Excessive preload destroys bearings prematurely, while insufficient preload can allow "wobble" of the ring and pinion gears with respect to each other, creating noise, at best, or destroying the gears, at worst.

A good and easy method for checking that preload is close to what it was before removing the nut (too late, in your case, unfortunately), is to measure the torque needed to turn the pinion with wheels free, then tighten the nut after new seal installation until similar torque exists to turn the assembly. Some will argue here, claiming the new seal imparts lots of drag; actually, not so, a worn seal imparts almost as much drag as a new one, and the seal drag is only a small part of the bearing preload torque, perhaps 10% or so.

Hope this info will be of value to you. Please ask if I can supply any other info for you! I await the inevitable clash if dissenting opinions now from others..........imp

Notice how closely "pinion" and "opinion" compare to each other----very appropriate!!
 




OneLever

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imp your mind is like a window into a world of knowledge.

If the pinion seal surface is grooved to any degree, the seal may be installed to a greater or lesser depth, in order to secure a fresh, un-grooved surface for the seal lip.

How much can the installation depth of the inner diameter be varied? Does this involve moving the inner and outer diameters of the seal simultaneously. Or must the inner diameter of the seal be bowed one way or the other slightly?
 




imp

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imp your mind is like a window into a world of knowledge.Gosh! And I always thought it posed a view into the world of perversion, rather......:rolleyes:



How much can the installation depth of the inner diameter be varied? Does this involve moving the inner and outer diameters of the seal simultaneously? Or must the inner diameter of the seal be bowed one way or the other slightly? Seals are mechanically constructed assemblies having, generally, a metallic outer ring which is press-fitted into a housing, the inner part being some type of rubber, whose location on the shaft to be sealed depends upon the physical location of the seal's outside diameter. (Hopefully, your intent here is not to set a trap for me.....). As you know, seals usually consist of a rubber (elastomeric) element bonded to a metal "case" or channel, which may usually be driven in to it's bore to a shoulder, or seated depth. Sometimes, no shoulder in the housing exists. At any rate, there is usually sufficient length along the smooth surface of the shaft on which the seal "lip" rides, and the bore in the housing into which the channel is driven, to allow locating of the channel (and therefore the lip, also), in a slightly different location from the original, thereby avoiding the wear "groove".

(It happens that, long ago, I worked for one of the major producers of oil seals and gaskets....a story for another time, to be told only if asked for.....I tend to talk too much! :( imp
 




Henre

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Thanks Imp and OneLever for the thoughts! Just a followup note.

When I installed the new pinion seal, I did not actually hammer on the new one. Rather I took the old seal and turned it upside down, placed it against the new one, and hammered on the old one evenly all around until the new seal bottomed out in the differential case shoulder. By the way I noticed (unfortunately after installation of the new seal) the original seal had a very lite coating of sealant (red) where the metal lip mates with the housing.

Next time I would place sealant on the lip even though it is a press fit. As well as on the flange nut.

Thanks again. Very informative! Henre
 




Henre

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A followup.

After another 300 or so miles, the pinion seal remains dry. Hopefully, the leak is fixed for now.
 




Henre

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A followup.

After another 1300 or so miles, the pinion seal remains dry.
 




imp

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A followup.

After another 1300 or so miles, the pinion seal remains dry.

From this, one can figure the pinion bearing preload is within an acceptable range. If too tight, the bearings would have overheated by now; if too loose, the gears would likely have become damaged by now.

The pinion in 1500 miles has rotated round and round approximately 4 million times! imp
 




Henre

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Thanks for the thought. Upon reflection, I wish I had tightened the pinion flange nut one-half turn past the 7/32 inch depth that existed at disassembly to take up wear.

I notice a slight whine when backing off the throttle; but it may have been there before the fix.

I just installed a new set of tires which did wonders for reducing drive train noise.

Henre
 


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