There have been several threads recently on leaking pinion seals including one of my own. While there are some decent videos on youtube there was not one for the F150 and I could not locate a write up either so here is mine.

My truck is 4x4, has a front level and has an extra leaf in the rear so it sits up higher than stock. I don't have access to a lift so I drove up on a couple of 2x8's under the front tires to get a few more inches of clearance. You will need all the clearance you can get to work. Be sure and block the wheels and set the parking brake!

Most rear ends are either 8.8 or 9.75. You can identify which rear by looking at the door sticker. Mine indicated a B6 axle which is the 9.75. Google is your friend here.



There are four 12mm bolts that hold the driveshaft to the flange. You will need a 12mm 12 point socket/wrench to remove them. Be sure and mark the drive shaft and the flange. Everything needs to go back exactly like it was. Notice the double marks with a Sharpie.



Once all four bolts are removed the driveshaft should slide out of the way. Mine seemed to be glued on and even a few light taps with a rubber mallet and prying with a screwdriver wouldn't break it loose. I got a bottle jack and put it under the driveshaft. A few strokes of the jack handle was enough upward pressure to break it loose. You can remove it totally if you need to or just lay it over to one side like I did.

Once it is off it should look like this.



Notice I marked the flange, nut and pinion with a red Sharpie, I finally found a black one and went back over it. Nail polish and paint will work fine too.

In addition to the marks be sure to count the number of threads exposed on the pinion. The nut needs to go back in the exact same spot with the exact same pressure so the bearings don't end up overloaded and cause future problems. I had five threads exposed on mine.

Next you will need a 1 1/8 socket (this nut may actually be metric but I did not have any metrics that big and the 1 1/8 fit fine). Mark the socket also so it lines up with the nut and flange marks.



As you turn count the number of times that the mark on the socket passes the mark on the flange. Mine was 16 and 3/4 turns.

Once the nut is removed you will need a puller to get the flange off. I tried a jaw type puller at first and it was just not working. My flange was on there tight! I got a steering wheel puller and it worked just fine.



Once the flange is removed you will either need a seal remover tool or a good old screwdriver and hammer like I used. Just work your way around the seal until it pops out.



Once removed it should look like this.



I took a clean rag and wiped everything down really good before installing the new seal. You do not want any dirt or grime getting in there.

To install the new seal you may have to give a few light taps with a hammer to get it set. Very light taps you don't want to dent or damage the seal. I then used a 2x4 that I had drilled a hole through the middle of with one of those saw tooth bits that you use to drill door **** holes in doors. I put this over the pinion on the seal and gave even hits all the way around with my hammer until the seal was flush.



Everything now goes back on in reverse order. I used my 2x4 with the hole and to get the flange started back on the pinion. Make sure all your marks line up again!

The flange would only go on so far so I put the nut on and started to tighten it down. I did put a dab of blue thread locker on the pinion threads to make sure it would stay put. Line the mark on the socket up with the mark on the flange and the nut and start counting turns.

This thing was a bear going back on but I finally got it there (16 and 3/4 turns for me) and made sure my number of threads on the pinion was five just like I started with.

Once the flange is back in place attach the driveshaft in the same position lining up the marks you made using the four 12mm bolts.(Things can get off slightly and you may have to put the truck in neutral to rotate the driveshaft to get the bolt holes to align. BE CAREFUL, BLOCK TIRES) I applied a dab of thread locker to the bolts and tightened them back up.



As you can see from my pictures I had a pretty good amount of spray from my leak. You will need to add some rear end fluid 75W-140 and I went ahead and added a bottle of Motorcraft XL3 friction modifier also. You may want rubber gloves, don't spill the modifier on you it smells like death warmed over!!!

The fill plug is located on the front of the differential on the driver side.



Remove the plug and fill slowly. Once you get some overflow stop and let it run out until it quits. Then reinstall the plug.

A couple of other things to mention is that you will need a drip pan. When you pull out the old seal there will be some run out and also for when you fill back up through the plug. You might also want to take this opportunity to grease the slip yoke where it goes into the transmission since the driveshaft is loose. Get a can of brake cleaner to spray everything off when done.

Last thing is you want to check the axle vent tube to make sure it is not clogged and was the cause of the seal failing from built up pressure.

I hope this write up helps someone. If anyone sees anything I missed just chime in!

 

thanks for the write up! I'm tackling this next week since I need to figure out whats going on inside my axle housing. You are right about the smell, its absolutely horrible and seems to stay on your hands forever!!!

I think the nut is 30mm one but obviously the 1 1/8" socket works fine.

 

I recently complained about the same issue, thanks for the write up! Will need to try it myself one of these next days I get off work.

 

Other than my using a punch to mark the flange / nut / pinion shaft .... that's it as I've posted before. I'm sure many will find the pics extremely encouraging. Of late here: https://www.f150online.com/forums/20...r-leaking.html

Good Post!

 

Thanks guys! It's really not that bad of a job, just takes lots of elbow grease.

 

Good stuff....pretty much how I did it. Had to rent the gear puller but other that, easy job.

 

I did read your post in my other thread and watched a video or two on youtube. All were helpful for sure!

 

Your pictures put yours over the top though. Many times I start a job and plan to take pics and soon it seems I'm done and no pics get taken?

 

Nice write up, thanks. I was just under the truck checking something else and noticed mine leaking.

 

Hope it helps! Seems to be a lot of them leaking on the 04-05's latley. I guess about 7 years is as long as the seal will last.

 

I hope to do the replacement soon and will see if I can use the torque stuff from the manual (below) and your method and see if I get the same result. I'll report back here.

This is from the manual:

During Removal:
"Remove the rear brake drums. (This is so they don't drag and disturb the torque measurment)

4. Install an inch-pound torque wrench on the pinion nut and record the torque required to maintain rotation of the pinion through several revolutions.

5. CAUTION:
After removal of the pinion nut, discard it. A new nut must be used for installation.

For Installation:
Under no circumstances is the pinion nut to be backed off to reduce preload. If reduced preload is required, a new collapsible spacer and pinion nut must be installed.

Using the special tool to hold the pinion flange, tighten the pinion nut. (This is just an arm like bar that is bolted to the flange to keep it from rotating)

Rotate the pinion occasionally to make sure the cone and roller bearings are seating correctly.

Install a Nm (inch-pound) torque wrench on the pinion nut.

Rotating the pinion through several revolutions, take frequent cone and roller bearing torque preload readings until the original recorded preload reading is obtained.

If the original recorded preload is lower than specifications, tighten to the appropriate specifications for used bearings (8 to 14 in-lbs). If the preload is higher than specification, tighten the nut to the original reading as recorded.

 

Yeah, you have to do that if you replace the NUT as no two nuts are "exactly" the same, and at best .... one still will not have the punch marks.

Just pointing it out to any who read in a hurry while doing the job .....


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My turn... mines leaking now too

 

At least yoor '04 is just starting. My '07 did last summer at 6yrs old. Not very happy with the 'superiority' of my 2007 compared to the 2004 I had.

 

does anybody know what I can do if I didn't mark or count threads? my 06 f150 with 9.75 seal was leaking so I pulled and put in new seal, but I pulled an idiot move and didn't mark it. am I totally screwed?