Post edited 2:02 pm – February 4, 2010 by notoriousDUG

---

a gateway to a cleaner driveway…

Look under pretty much any well loved (re: abused) 4×4 and the chances are high that there are going to be some ugly little leaks.  Seems that submerging your undercarriage in water, mud, sand and whatever else you can find is not the best thing you can do for all of the seals down there under the rig trying valiantly to keep your fluids inside of various components.  One of the most common seal failures under a 4×4 is the pinion seal; being on of the lowest seals on the rig it gets a ton of abuse plus driveline vibration can help shorten life; I don’t think I have ever seen an older, well used, rig with a good pinion seal on it.  Now responsible people accept this as part of ‘wheeling and will keep up on items like this as part of routine maintenance. 

Me, not so much.

This lackadaisical attitude is what recently left me with a daily driver that was virtually pouring gear lube out the pinion.  The whole underside of the truck was coated to the point I could smell it burning off the exhaust!  An upcoming drive of some distance, as well as some interesting growling bearing noise, made me decide that I should probably get around to swapping out the bad seal on this thing.  Because I was bored and crave attention and validation I decided to take some pictures and write it up as well.  Follow along at home and you to can be a pinion seal rock star.

Now, if you search around for write ups on pinion seal replacement you will find a ton of information that implies I seemed to have missed some important steps, and parts, in my replacement.  Hence the ‘Quick and Dirty’ part of the title, while many of the steps and parts you see in other write ups are the ‘by the book’ way of doing it that does not mean there is not a perfectly viable alternative.  My method, with pretty basic tools, took all of an hour to do and required a grand total of about 10 bucks in parts.  I have used this method on more pinion seals the I care to count and have not had a failure but I can not promise the same mileage to you.  If you are a nervous nellie or can’t deviate from the maintenance manual then this may not be the method for you, if it gives you piece of mind the extra time and parts are worth it.

One more disclaimer:  I did this write up on a Toyota diff but it will still apply to pretty much any differential out there.  Your yoke and shim arrangement may be different, or you may even have a crush sleeve style, but the basic are the same regardless.

First step is to disconnect the driveshaft from the pinion yoke; if you can’t figure out on your own maybe you might want to think about taking the pinion seal job to a shop.

What you are left with minus the driveshaft will be some form of  pinion yoke with a big nut in the middle of it such as below.

The large nut in the center is actually threaded onto the pinion itself and, as well as holding the yoke on, is also responsible for setting your bearing preload on the pinion. To get off the pinion yoke and get to the seal we are going to need to remove that nut; this is less then an easy task.  Not only is it big and put on there with considerable force but it is a lock nut, the end of it is pinched closed to bite on the threads of the pinion and help keep it from backing off.  Good when you are driving around, bad when you are trying to take it apart.  There are several methods for holding the yoke and pinion still while turning the nut as well as a good selection of special tools to do so.  I prefer to take the simple route, a big booty impact and the vehicles parking brake.  If I have a really stubborn one a big pipe wrench usually does the trick but rarely do I have to use it.

A trick a friend showed me for when you are stuck on the side of the road with no air tools is to put a big pipe wrench on the yoke with a long pipe over the handle and a big pipe on the handle of a breaker bar on the pinion nut. Jack the rig up as high as you can, brace the two pipes on the ground in a manner that when you lower the vehicle they turn in the appropriate directions and lower it again.  Unless your junk weighs less then a Yugo this should break the nut loose. 

Once the nut is removed you should be able to pull the pinion right off on most axles.  Sometimes you need a little bit of persuasion from a hammer but 90% of the time it comes off easy.  Some large differentials can require a puller but they are the exception to the rule.  There is a large, and important, washer under the pinion nut, be careful not to loose it.  With the yoke off you should have excellent access to the pinion seal.  Looking closely you should be able to see the seam between the housing and the seal body.  Insert a screwdriver into the seam as pictured

http://farm3.static.flickr.com…..ca.jpg/img

and carefully tap it into the seam and work the seal out of the housing.  When tapping on the screwdriver or punch you want to try and pound into the seal and away from the housing; if you get into the housing you can gall it and end up with a small leak or extra work to smooth out the damage.  This is especially critical on aluminum housings.

When the seal pops out expect some fluid to come out as well; I suggest a drain pan unless you are at somebody else’s garage.  Another hillbilly hint is that if you can park with the pinion pointing up hill it will prevent the flow of oil.  Depending on the design of your differential there may be some shims or a crush sleeve on the pinion; leave them alone they need to stay there for it to go together properly.

http://farm3.static.flickr.com…..ca.jpg/img]

and carefully tap it into the seam and work the seal out of the housing.  When tapping on the screwdriver or punch you want to try and pound into the seal and away from the housing; if you get into the housing you can gall it and end up with a small leak or extra work to smooth out the damage.  This is especially critical on aluminum housings.

When the seal pops out expect some fluid to come out as well; I suggest a drain pan unless you are at somebody else’s garage.  Another hillbilly hint is that if you can park with the pinion pointing up hill it will prevent the flow of oil.  Depending on the design of your differential there may be some shims or a crush sleeve on the pinion; leave them alone they need to stay there for it to go together properly.

[img]http://farm4.static.flickr.com/3104/2377767037_7f6bd05895.jpg" alt="http://farm4.static.flickr.com/3104/2377767037_7f6bd05895.jpg" alt="http://farm3.static.flickr.com…..ca.jpg/img]

and carefully tap it into the seam and work the seal out of the housing.  When tapping on the screwdriver or punch you want to try and pound into the seal and away from the housing; if you get into the housing you can gall it and end up with a small leak or extra work to smooth out the damage.  This is especially critical on aluminum housings.

When the seal pops out expect some fluid to come out as well; I suggest a drain pan unless you are at somebody else’s garage.  Another hillbilly hint is that if you can park with the pinion pointing up hill it will prevent the flow of oil.  Depending on the design of your differential there may be some shims or a crush sleeve on the pinion; leave them alone they need to stay there for it to go together properly.

[img]http://farm4.static.flickr.com/3104/2377767037_7f6bd05895.jpg" />

While your differential spews nasty, bad smelling gear lube all over (don’t you ever service that thing?) it may be time to give your pinion yoke some love and attention.  Carefully inspect the sealing surface (the shiny bit that the seal rides against) for grooves, discoloration and pits.  Off roading gets all sorts of grit into the seal that can abrade the seal surface and put a grove in it preventing the seal form properly sealing.  Notice my pinion yoke had some ugly coloration and in the center of that a small groove:

Rule of thumb is that if you can catch a fingernail in the groove you should replace the yoke.  However if you are cheap, like me, and the grove is not too deep you can take some emery cloth and clean it up to smooth out the groove.  This is not a sure fire fix, if the groove is bad enough no amount of polishing will solve the problem.  As you can see mine cleaned up pretty good but I still have a bit of a groove.

Also take this time to clean, and clean good, the entire pinion yoke.  Make sure to get inside of it on the splines the best you can, this will be important later.  I also like to clean all the fasteners for the driveshaft and the pinion nut at this time.

Now it is time to start putting stuff back together; this is also where I depart the script.  Many people insist that you have to install a new pinion nut and, if applicable, crush sleeve.  While I will not say that is a bad idea I will say that if you have no problems with how the rear is set up and the pinion nut has not been run on and off to many times then you are fine with what you have.  My personal test for the pinion nut is the same one the FAA recommends for self locking nuts:  If you can thread past the locking mechanism by hand it is bad; not even I would use it.  As I said before I have had good luck for years doing it like this but if you are not comfortable with it do it to your standard, I mean what the hell do I know right?

Also, if you are feeling brave and the outer pinion bearing was bad now is the time to replace it.  Simply pull out any shims, oil slingers or crush sleeves over the bearing, remove it and install the new one and then put shims back in place.  All of the setting should remain the same when you install it.

After you make sure all the parts that need to be inside the pinion housing are still in there you are ready to install the seal.  Almost, first you need to get all the nasty oil out of the way and clean off the housing and the pinion shaft itself.  Make sure and get the splines good just like on the yoke; it’ll be important later.  Once you are all cleaned up then you can put the seal in.  I like to put a little Permatex Aviation Sealant (the brown goo in a jar) around the outside of the seal but it is not required.  Depending on the specific differential there should be some kind of lip either in the housing or on the seal that is where you install it to.  Carefully tap the seal in with a small hammer.  Sometimes it can be hard to get the seal started square and it will not want to go in; do not haul off and beat it in with the hammer! You will end up deforming the seal and it will have a very short life, if it even seals completely in the first place.  They make special seal drivers for this but often a block of wood or properly sized pipe will help line the seal up and get it started.

With the seal in and firmly seated you can now prepare the pinion yoke for install.  One trick I learned years ago was to take some RTV and smear it into the splines of the yoke, doing this will prevent a potential leak out the center of the yoke.  I also smear some grease on the seal face to help in slide into the seal.  After that make sure the pinion splines and threads are clean and slide the pinion on and install the nut making sure the washer is under it.  When installing the nut I always use a little bit of Loc-tite, this is a high vibration area and even with the locking nut I like the insurance.

You can find 50 different ways to judge the torque on the pinion nut, I choose to use common sense.  I simply run it down with the impact and check the preload (how hard it is to spin).  If it is super tight, almost too tight to even turn, I know I need to add shims or get a new crush sleeve and really check out the preload.  If it flops around side to side it is to loose and I need to get in there and check the shims or tighten the nut more.  Sounds kind of tricky huh?  Well I’ll be honest with you kids, cause I like ya, in my world if the pinion has no side play, turns about the same as it did before I took it apart and feels smooth I am running with it.  In all reality you have not changed any of the variables that will affect gear setup; as long as you get the nut at tight as it was before, and the gears where OK to start with, it’s going to be fine.

Now another important bit.   If I am reusing a pinion nut I also like to ‘stake’ the nut in place.  ‘Staking’ is the act of using a punch or chisel to peen over the edge of the nut to help keep it from loosening.  To do it just put a small chisel at the edge of the nut as shown in the picture and give it a whack with a hammer.  I like to do it twice, 180* from each other.

At this  point you can hook up the driveshaft (use some loc-tite on the bolts here as well) and service the diff (if you parked on a hill to avoid loosing oil put it on level ground before you check the level) and enjoy some leak free driving.

I also suggest that, unlike my lazy butt, you clean off the housing so you can see if it is leaking after the repair.  I find the feeling of accomplishment is kind of missing when it is almost as oily after the job as before.

Now go out and fix that POS that is leaking all over your drive.