Howdy all,

I changed my rear pinion seal yesterday. When reassembling everything, I found out the new pinion nut the dealer sold me to replace the old one that's supposed to be discarded was the wrong thread. The ID of the threads was withiin a few thousandths of the original, but would not go on the pinion gear.

Closer inspection revealed the thread pitch on the original was 1.25mm while the 'replacement' measured 1.5mm. Needless to say, I had to reuse the original, using blue locktite until I get the right one which won't be until I return from a 1500 mile trip pulling a trailer. Sure hope I don't have an issue with this.

Dealer gave me what he said was the nut for a 9.75" rear end...there couldn't be 2 different pinion threads/nuts, could there? For what its worth, my rear end code is H9.

Can anyone explain what got mixed up? Comments on reusing orogonal nut for 1500 miles?

 

H9 is the old code for an 8.8" limited slip diff w/3.55 gears. If he sold you a pinion nut for a 9.75", that's probably why it doesn't fit. I'm surprised the seal fit.

Which of these diff covers looks like your axle's?

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You should be OK to reuse the nut for a little while, but how did you torque it? If you didn't properly set the pinion bearing preload (which normally involves a new crush sleeve & an inch-lb torque wrench), then you could damage the gears in just a few miles. Read these:

http://www.fordracingparts.com/downl...And-Pinion.pdf
http://www.differentials.com/install.html

 

Thanks for your response! I can't tell what the stock diff cover looked like 'cause when i got it, it already had a chrome cover on it...so tag missing too, hence I guess my issue.

Spent an hour on Tue. sitting at the dealer's parts counter trying to get it figured out. Never did by axle code, or VIN. Finally the parts guy took my nut and went out to see his rear end man and came back with the proper fine thread version of the nut. Other than the thread pitch, the only other visual difference was the blue patchlock compound on the fine thread nut and the green patchlock on the coarse thread one. He gave it to me and it fits fine.

I have a set of factory manuals and after I pulled the flange away from the bearings just enough to get bearing end play, installed the new nut and set the preload to the max for used bearings (16 in-lb) so I hope I'm good to go.

What was surprising to me was how low the torque on that nut was (probably less than 80 ft-lb) to get that 16 in-lb preload. I was expecting to need more torque than it took...I can see why the nut is both staked and has patchlock applied.

And so far, no leak...I did find a nick on the flange right close to the seal wear witness mark, so before I put 'er back together, I polished the seal surface and epoxied in the nick, then polished the epoxy smooth with 600 paper. Time will tell how this will work, but I did this to a Jeep rear axle shaft bearing seal surface once and it held for years, still no leaks when I sold it 15 years later.

 

You can also ID them by the cover bolt pattern or the gasket shape. Look around drivetrain.com at the Ford axles.I wouldn't drive it. That's not enough to keep the pinion gear in place. You need a new crush sleeve.

 

My 9.75 has a 3.55 gear with limited slip, and its code is H9.

 

I'm in the middle of a gear change myself, 3:55 to 4:56. I'm working on a 97 F-150 with a 9.75 rear axle. I understand torquing the pinion nut for bearing pre-load but you have to torque the nut enough to crush the sleeve and this is where I'm confused. I've gone up to 140 ft-lb's and the crush sleeve wont crush and I'm at my max on the pinion pre-load. The one removed was crushed but the new ford ones wont. What am I doing wrong?

 

now I see the problem....the new pinion is slightly different from the original. The 4:56 pinion is machined 7mm lower where the crush collar resides compared to the original. But everything fits and I was able to get proper gear mesh and backlash. Has anybody gone through this problem with motive gear before? How about machining a 7mm spacer to go under the crush collar? Can anyone offer any advice?

 

If the gear is machined wrong, send it back.

140 lb-ft isn't enough to keep the pinion in line; IIRC, the minimum is 180.

 

so torqueing the pinion nut to a minimum of 180 ft lb's will still allow me 15 to 20 inch lb's of bearing pre-load. I take it it takes 180 to crush the collar and after that the proper torque is applied to the nut to gain the bearing pre-load. Well what If a solid spacer is used.......is it still a minimum of 180 to keep the pinion together and proper bearing pre-load can still be achieved?

 

I thought you said you had already reached max preload at 140 on the nut.

IDK if a spacer is acceptable, but I'd complain to the gear mfr./supplier anyway.