I have a 99' supercab dually w/ a dana 80.I had it for about two months.I noticed the pinion seal is leaking.I had it on the interstate for the first time and i have a whine.Im still not shure if its the agressive tires or the pinion bearing.I was just wondering if this is common.

 

My 99 dually pinion seal started leaking at 25,000 miles.. dealer fixed it under warranty. No problems since..

 

I have replaced mine twice in the last 4 months, bearing seems fine, I think I just got a bad seal the first time I replaced it. This one seems to be holding fine.

 

mine was wet around the pinion, then my gears went out. replaced it and the gears no leaks now

 

mine is leaking ..........I just noticed. How do you replace it???????

 

You need to pull off the pinion yoke and then you can remove and replace the seal. Then you have to put a new crush sleeve in and adjust the preload on the pinion bearings. Its not a simple task because if do not set preload correctly you will toast the bearing and could destroy the ring and pinion.

 

I dont think the dana 80 has a crush sleeve,the nut just gets torqued to 475 ft/lbs.

 

My parts book says the dana 80 has a crush sleve, although I've never been inside of one. I've done quite a few pinion seals in the past. Here's how I do it.

Replacing the pinion seal is not for the faint of heart, at least the first couple times. There's big $$ in the diff's. (My disclaimer)

You will need a very acurate dial-type inch pound torque wrench to replace the pinion seal. Clicker types will NOT work, and a way to hold the pinion flange when removing and installing the pinion nut. I made one, big square with a long handle.

You need to take a rotational reading on the pinion flange with the brakes retracted and the axles removed. Usually 8-15 inch pounds, most repair manuals list the amount. My inch pound wrench has a tattletale that stops at the highest reading so you don't need to watch the dial. I do it a couple times looking for a good feel on the wrench. Be smooth, No jerking.

Remove the nut and inspect the pinion flange where the seal rides. If there is a groove, replace the flange. (Highmark18 this ones for you).

Count the number of threads exposed on the pinion nut. Be accurate and mark the location on the pinion itself where you counted the theads.

The new pinion seal will add about 5 inch pounds of torque (also listed in the repair manuals), so you need to add that to the number you got above.

After installing the new seal, be sure to lube everything, tighten the pinion nut back to the desired location (exposed threads above). Sneak-up on it, No impact wrenches. You're going to sweat a little. LOL Take rotational reading until you have the desired amount. If the repair manual lists a specific pinion nut torque then go ahead and use it, but the rotational torque is what you're looking for.

If you didn't install a new pinion nut be sure to add some locktight just to be sure. Also, I like to add a litte sealant to the back of nut to keep the diff fluid from seeping past the threads. Some nuts have a rubber seal on the back just for this reason.

I may have forgot something, however I' sure someone else will chime in.

BTW: You don't need to drain the oil, but it's a good time if you want to.

 

You might make sure your vent is not plugged before you do anything else. I have had this happen before on a 9" rear.

Mark

 

When I replaced mine, I specifically went to the dealership and asked about re-tightening the yoke nut. The Service Manager (who is a friend of mine) plainly told me "Just tighten it up, give it a few hits with the air gun, and you are done, that is all we do." That is all I did on this one, and the one I did a couple years ago (which now has over 240,000 miles on it.
By no means am I saying you are wrong, just stating what I was told. Your way is probably way more precise.

 

Darn good point. I totally forgot about that one. Too much pressure in the diff and fluid goes out the weakest seal.

 

My service manual says that for the sterling 10.5 rear you set the preload by the resistance of rotation just like you said.The dana 80 however say to torque to 475ft/lbs.I ordered and recieved everything from my ford guy,and he didnt say anything about a crush sleeve either.I guess ill call to make sure.I looked at the manual first and didnt ask for a sleeve,but with a torque spec like that on the pinion nut i dont see how there could be a crush sleeve.

 

I just called the ford dealer and they said they have no listing for a crush sleeve for my rear.Maybe the older ones do.

 

I replaced my rear seal about a year ago, when I got my truck, and I also didn;t have any crush sleeve. But my 92 did.

 

Thats funny my old dually was a 92' also,and my new one is a 99'.I think my old truck had a 10 1/4" ford rear in it.