Changing the Pinion Seal - 1974 Ford 9 Inch 2WD

May 18, 2018

Today I am going to replace the rear pinion seal before I wash, prep and paint the rear frame half. This rear end is from a 1974 Ford F100 two wheel drive. As I mentioned before, it appears this rear pinion seal failed a long time ago.

I read on another site that you should mark the position of the drive line to the pinion and the pinion to the rear end housing. They said that if you do not do this there could be wobbling of the drive line at high speed. That makes sense and to me and it was well worth the 2 minutes it took to make the alignment markings. I used a scribe to scratch into the metal of the u-joint and the pinion. I also put a scratch on the pinion dust cover and rear end so that it can go back into the exact spline I took it out of.

The next step was to remove the drive line form the pinion. 4 nuts hold the u-bolts to the the universal joint and the pinion. I removed those nuts and pull the u-bolts. I was careful to hold the drive line so that it did not fall to the floor (which will inevitably cause the caps for fall off the u-joints and the needle bearings to fall out).

After removing the drive line I removed the u-joint caps to inspect the u-joint. The u-joint had groves worn into it, which to me, indicates replacement. I will do this later when I service the transmission.

Next, I put a pan under the rear end to catch the oil that will spill out of the rear end. The nut that holds the pinion in place should have been torqued to 250 pounds (for mine). I discovered that mine was barely hand tight. My guess is that this is the reason that I had the leak and bad seal. Once the nut was off I pulled the pinion straight out.

Next I removed the pinion seal. It is made of a light gauge steal and came out easy with a center punch and hammer. I made sure that I did not damage the shaft or housing as I was banging it out. You can see in the images below that there is a lot a crud that fell on the shaft. This is just dirt and crud that fell during the seal removal, it was not metal shavings or anything that would indicate bigger issues. I just wiped it all off before putting in the new seal.

The seal I used for this rear end was a Timken 7044NA. I set it in place, even on all sides and then slowly tapped it in place with a small ball-peen hammer. It took a few tries to get it right, but tapping very lightly in a circular motion got it in place in short time. I know that if I hurry this step I would damage the seal or worse, the housing. I just took my time. Once the seal is in place, I took some of the oil from the rear end and lubed the rubber part of the seal. 

I applied some blue lock-tight to the threads of the pinion shaft before aligning it to the marks that I put on earlier. I put the nut back on and tightened it to about 250 pounds torque. Then I just put the u-joint back, aligning the marks that I put on earlier and tighten the nuts back on. I did not add oil to the rear end or torque the u-joint nuts correctly at this time... I will be doing that along with replacing the u-joints front and back when I service the transmission later.

Below is a picture of the new pinion in place after I pressure washed and de-greased the rear end.