Replace pinion seal in 742 case problem

[Sixpactogo]

My pinion seal was leaking. I purchased a new one from Dr Diff. I dropped the driveshaft and removed the pinion nut with a air impact wrench. Knocked out the old seal. I scraped and cleaned up the recessed area and smoothed out the ridge from the old pinion seal with an emery cloth. I noticed some dirt on the bearing and thin shim so I pulled them out and cleaned the debris and re installed it. I installed the new pinion seal then the yoke, thick washer and nut and hit it with the impact wrench and could no longer turn the pinion. I backed off the nut a little and could then turn the knuckle again. I used all of the same parts except the seal. Any ideas as to why it won't turn when torqued down? I have never run into this issue before?

 

[dvw]

The pinion preload shims set right behind the front pinion bearing on the pinion shaft. My bet is you lost one. They can stick to the bearing when it's removed.
Doug

 

[R/T Boy 67]

The wording you used suggests the shim was on the outside of the bearing. The shim needs to be on the inside of the bearing. Perhaps, the nut was not fully tightened by the previous installer.

 

[Sixpactogo]

That was my first thought too but I searched the small area and never found another shim. I bet your are correct though. Guess I better call Cass and order another pinion seal. It is coming apart again. Thanks for the reassurance.

 

[mattsmopars]

Do you know what the torque was before on the nut? If it came apart and went back exactly the same as far as the pinion depth shims are concerned, the only thing I can think is maybe you are torqueing it down tighter than it was before. A lot of times when you first torque them it will feel tight until you rotate it a few time by hand because the bearing and everything is being seated, but after few rotations if its correct it will loosen up, if not you have a problem. Normally I try to torque to the minimum torque spec first and move up if necessary.

 

[Sixpactogo]

The wording you used suggests the shim was on the outside of the bearing. The shim needs to be on the inside of the bearing. Perhaps, the nut was not fully tightened by the previous installer.

I was pretty sure I saw a shim on the backside of the bearing but maybe was wrong. The nut was tight. It had the original factory leather seal so I doubt it had ever been off before.

 

[Sixpactogo]

Do you know what the torque was before on the nut? If it came apart and went back exactly the same as far as the pinion depth shims are concerned, the only thing I can think is maybe you are torqueing it down tighter than it was before. A lot of times when you first torque them it will feel tight until you rotate it a few time by hand because the bearing and everything is being seated, but after few rotations if its correct it will loosen up, if not you have a problem. Normally I try to torque to the minimum torque spec first and move up if necessary.

I do not know the original torque. I'm guessing around 250 lbs though by the effort my impact wrench needed to remove it. I'm almost certain I put the shim in wrong. It is about the only thing possible. I have replace quite a few of these before but never had this issue before. Thanks for the reply.

 

[Fran Blacker]

Order a few shims if you don't have any. If take apart now to check for buggerd shims.

 

[gtx6970]

shims between the bearing and the yoke?
never heard of that

or did you remove the bearing itself ?

 

[dadsbee]

Is a 742 not a crush tube? (or is that the 489). Mark the nut postion and put it back exactly where it was.... or you're pulling it all apart..

 

[R/T Boy 67]

741 and 742 are shim types. No crush sleeve.

 

[Sixpactogo]

Thanks everyone for the tips. It ended up being a brain fart on my part. When I pulled the bearing to clean some gunk out, I thought the shim was on the backside of the bearing instead of the front. Pulled it back apart and reinstalled the shim in front and put it back together. Hit it with the impact wrench and...Viola......Back to normal. I was able to save the seal since it went in pretty easily and came out the same. I smeared a little black RTV on the outside lip and popped it back in. The new seal I got from Dr Diff is no where near as meaty as the old factory mopar seal was. If this one leaks, I see there are a couple of the heavy duty factory PN's on Ebay available yet but I'm hoping I won't need it.

 

[dan juhasz]

National still makes the correct leather seal for a 742

 

[Fran Blacker]

C/R made the original seal on my Satellite. The seal PN starter 18xxxxx, your original probably has it?

 

[493 Mike]

Thanks everyone for the tips. It ended up being a brain fart on my part. When I pulled the bearing to clean some gunk out, I thought the shim was on the backside of the bearing instead of the front. Pulled it back apart and reinstalled the shim in front and put it back together. Hit it with the impact wrench and...Viola......Back to normal. I was able to save the seal since it went in pretty easily and came out the same. I smeared a little black RTV on the outside lip and popped it back in. The new seal I got from Dr Diff is no where near as meaty as the old factory mopar seal was. If this one leaks, I see there are a couple of the heavy duty factory PN's on Ebay available yet but I'm hoping I won't need it.

Can we assume by "front" you mean toward the engine?
Mike

 

[dvw]

Obviously the problem has been resoolved. The sequence of removal is; nut, washer, yoke, seal, bearing, shim(s). To me that means the shim is behind the bearing.
Doug

 

[Sixpactogo]

Can we assume by "front" you mean toward the engine?
Mike

Wow. who would have thought this could have caused so much confusion. To me, "in front" means ahead of. No we can't assume toward the engine since facing the pinion you are looking toward the rear or toward the carrier with the engine behind you.

 

[Sixpactogo]

Obviously the problem has been resoolved. The sequence of removal is; nut, washer, yoke, seal, bearing, shim(s). To me that means the shim is behind the bearing.
Doug

I agree with the sequence. Sorry I confused you with my comment but the sequence gets reversed when going back together. I didn't spell it out correctly. I should have said, "shim, bearing, seal yoke washer nut."

 

[Sixpactogo]

National still makes the correct leather seal for a 742

The seal on the right is the National seal. It is rubber not leather. It is their part number 7216 replacing the 1828719 mopar part on the left.
It fits but is not near as meaty as the original part. The National seal looks exactly like the seal I got from Dr Differential which is also rubber.
Parts guy I got the National seal from told me that Precision bought out National or vice versa. He was unsure of who bought out who but they merged.
Either way, the new rubber seal is doing it's job. Hopefully it will last as long as the leather one did.

 

[Sixpactogo]

C/R made the original seal on my Satellite. The seal PN starter 18xxxxx, your original probably has it?

Yes. PN 1828719. I couldn't find a C/R seal. All the parts houses around here have National or Precision PN 7216. If this rubber seal starts leaking, I will go back to the Mopar leather seal. It looks way more heavy duty to me.