Replacing pinion seal 1950 Ford car

[azandy]

I'm replacing the pinion seal on my 1950 Ford car. The drive shaft is out, the pinion nut, shaft and u-joint flange are marked and wheels are off the ground. When I rotate the u-joint flange by hand it moves freely clockwise and cc about 6 degrees before I feel contact with the ring gear. Is this too much? How much play should it have? If it's too much can I fix it by tightening the nut a little beyond the mark when I put it back together?
Thanks for any responses.
Azandy

[Flathead Fever]

You need to check the backlash with the pinion flange bolted on. That should be done before you remove it

It should just have a little play. A rule of thumb for backlash is .001" for each inch of ring gear. This reading is taken at the outside edge of the ring gear. You should feel just a tiny bit of play back and forth. This allows the gears to expand with the heat and still leave room for a film of lubricant between them so the gear's teeth never actually touch.

I have not been into a '50 rearend but I've done at least 100 late model rearends. Tightening the pinion nut will not change the backlash. Decreasing the backlash is done by moving the ring gear closer to the pinion. Either by moving the carrier bearing shims from side to side or by moving side bearing adjusting nuts depending on the design.

The pinion bearing preload is set first. Then the carrier bearing preload and then the ring gear backlash last. Next you check the contact pattern. If the pattern is off then you move the pinion in or out just a few thousands. Go back and reset the backlash and check the pattern again. You might need to do this several times to get everything correct unless you have a pinon depth setting gauge specific to your rear end (which you won't have). A lot of time your pressing on and off the bearings over and over to change the shims. You don't want to do that, you can wear out parts. I did a lot of the same rearends at work so I honed out a set bearings so they were a snug slip fit. Then I could easily remove the bearings and change the shims. When everything finally looked good I installed the new bearings. The same bearing part numbers are "suppose" to be all ground to within .0001 of each other so the setup does not change with different bearings.

Your doing what you are suppose to do when you just replace the pinion seal so you do not disturb the pinion bearings preload. Too loose and the pinion gear will move and the two gears teeth will chew each other up. Too tight and the pinion bearings will overheat and fail. You have no way to correctly check the pinion preload unless the carrier and ring gear are out of the housing so you can rotate the pinion without it being in contact with the ring gear.

What your doing with the paint marks is trying to put the nut back in the exact same spot it was when it was removed. Put some "blue" lock tight on the nut to keep it from backing off. Push and Pull on the pinion flange to make sure there is no play in those bearings and that pinion gear cannot move at all except to rotate. If there is any play you didn't get the nut back in the correct spot.

Pinion bearing preload is different for new bearings than its is for used ones. Used ones are setup with slightly less preload. Preload is suppose be checked without the seal in place because you could mistake the dragging of the rubber seal with bearing preload. The truth is at work we always stuck the seal in and checked preload afterwards and we never had any problems. We lubed the seals so they would not create a lot of friction and I always set the preload to the upper end of the specifications which should have cancelled out any of the seal dragging.


I though of something else. Pinion bearing preload (the pressure on the bearings is accomplished two different ways. One way is with a crush sleeve. As you tighten the nut it begins crushing the sleeve between the inner and outer bearings putting pressure on them. The further use crush it the more pressure it puts on the bearings If you go to far you cannot back off the nut because you have already crushed the sleeve too much. Then you will need a new sleeve to start over. This is the kind of bearing preload that requires the nut be placed back in the same spot so you don't further crush that sleeve. The second way uses shims between the two pinion bearings. The more shims you add the more pressure on the bearings. I'm talking about making adding maybe .002" to. 004" shim at a time to get it just right. Because the shims cannot be crushed you don't need to worry about getting the nut back in the exact same spot. You torque it to specs and don't worry about where it ends up. We used a lightweight aluminum 3' pipewrench to hold the flange. The handle of the pipe wrench rests against the bottom of the leaf spring and prevented the pinion from turning while nut is torqued.

Make sure the excessive play you are feeling is just between the pinion and ring gear and are not worn-out spider gears allowing play between the ring gear carrier and the axles.

Don't forget to put a little gear oil on the seal and pinion flange so it does not run dry until some oil gets splashed on it. Also, clean the housing where the seal presses into and put a little coating of silicone around the seal before you drive it in so you do not end up with seepage between the seal and the housing. A "little-little-coating" of silicone you don't want it squishing out into your bearings. Modern pinion seals have a strip of sealant on them to prevent this. Make sure when you pound the seal in you don't knock out the tension spring out of the seal.

Finally, if the rearend is not making any noise I would not worry about the play. It falls under, "not broke don't fix"! Its not going to leave you broke down on the side of the road. It will start making terrible noises when it gets close to doing that. I've seen the fleet vehicles with excessive play continue to go for years without any problems. That's being driven overloaded and hard every single day.

[azandy]

Wow! A great response, I'm not about to break into the rear end so I'll just replace the seal per your suggestions. It was not making noise so I think I'll be okay.
Thank you
Andy

[Kurt in NJ]

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