replacing front diff: best way to reset pinion yoke nut?

[kestrelnh]

My front diff had a dental problem: it lost some teeth I've got what is claimed to be brand new 2.56 ratio one, and it looks at least freshly rebuilt. To take out the old one and put in the new I need to remove the pinion nut to take off the yoke in order to pull it through the rear diff mount. According to TM 9-3220-280-34 section 9-5 "differential replacement", I should measure the torque to rotate the new diff via the pinion nut, take off the lock nut, discard it, put the diff back in the truck, and use a new pinion nut and tighten is slowly under the torque to turn the diff is 2 ft-lb higher than it was when I took the nut off.

The new diff has no oil in, probably never has, and the output flanges are off, and feels like it may be just the tiniest bit notchy when I rotate from the yoke, but again... no oil. I can follow the instructions, but have also read that I should just mark exactly where the current lock nut is, and put it on exactly that amount, maybe a tiny bit more.

Who's done this before and can tell me the best path?

Thanks,

Jordan

 

[Action]

I can't tell you the best path, because I have only used one of those methods. I used the torque method with no issues. I had to change the yoke size.
I don't understand why you need to remove the yoke to change the diffs. The center mount only bolts to the top of the case.

 

[kestrelnh]

You're absolutely right. While the mount on my truck doesn't look that that (it's part 9 in the below diagram), what I thought was a full circle in the mount actually has a cutout at the top so I can slide the mount off. I missed the cutout in the grime and not having a proper work light setup. Plus the manual was saying things about if the front diff was being replaced the yoke and slinger needed removing, etc.. Thanks for the info. I was having a hard time believing they were going to make me remove the yoke to replace the diff, but managed to believe it anyway

 

[mdes0]

I had a similar issue earlier this month. Out of curiosity what dud you loose teeth on? Ring or pinion, or one of the worms?

I'm replacing mine with an ARB setup in the same diff housing, my ring and pinion are in good shape. I had a worm gear tooth chip and shattered all the work wheels on that gear.

Matt

 

[kestrelnh]

I had a similar issue earlier this month. Out of curiosity what dud you loose teeth on? Ring or pinion, or one of the worms?

I'm replacing mine with an ARB setup in the same diff housing, my ring and pinion are in good shape. I had a worm gear tooth chip and shattered all the work wheels on that gear.

Matt

Almost certain the pinion, but I'll double check when I get it apart. The truck was delivered with no oil in the front diff, so if took a real beating before I got it. It made it two years and a few thousand miles before before fully losing a tooth, but it had been grinding itself apart until then.

 

[Action]

OOps, I posted the rear mount pic.

 

[kestrelnh]

OOps, I posted the rear mount pic.

I'm grateful anyway. It made me look at the manual, which made me look at the truck

 

[kestrelnh]

You know, I have to stop saying things like "almost certain" because I'm proved wrong more often than right I got the diff out today, opened it up, and all the teeth seem to be there on the ring and pinion, which means the tooth I found probably came from inside the torsen.

I'm going to try to get the new one in this afternoon while my memory is fresh. Maybe a local shop will be willing to rebuild the old one, but I have a suspicion it will cost more to rebuild than sourcing another NOS diff, or used diff in good shape.

 

[kestrelnh]

So it looks like my new front differential has the yoke for a rear differential on it. Unless anyone knows of any clever way around this, it look like I'll be replacing the yoke with the old one and back to where I started hoping that my new inch-lb torque wrench does the trick.

 

[kestrelnh]

Been doing a bit more research. It looks like I may be able to frankenstein the front drive shaft by putting in later front section which has the 4" ujoint rather than the 3.5" ujoint. It wouldn't be bad idea to replace drive shaft carrier assembly which looks pretty ugly. It looks like people have the rear part of this shaft as part of an a2 drive train conversion. Can anyone confirm I can mix and match front and rear portions of the front drive shaft?

 

[86humv]

Been doing a bit more research. It looks like I may be able to frankenstein the front drive shaft by putting in later front section which has the 4" ujoint rather than the 3.5" ujoint. It wouldn't be bad idea to replace drive shaft carrier assembly which looks pretty ugly. It looks like people have the rear part of this shaft as part of an a2 drive train conversion. Can anyone confirm I can mix and match front and rear portions of the front drive shaft?

PM sent
Diff has numbers on ring gear....rotate it and look for the last numbers : 41-15 =2.73......41-16= 2.56.
Maybe there's a tag on cover bolts with ratio.

 

[kestrelnh]

Thank you! All the diffs are 2.56, I've checked that. On my A0, the rear diff has the larger yoke, and the broken front diff has the smaller yoke. The new front diff has the larger yoke. Per your pm, 12342620 drive shaft component should allow me to put the new front diff in without replacing the larger pinion.

Maybe I should have splurged on an A1, I'm going to get there slowly in parts costs anyway

 

[Mborkush]

I’m looking to change my gears from 2.56’s to the 2.73’s.
Any recommendations on who or where to start shopping for replacement gears? I’m going with a duramax so also looking for a decent “all purpose “ locker. Any recommendations?

 

[kestrelnh]

Well, at least one more part to buy for this conversion. The original rear part of the front diff mount won't fit over the larger 1330 yoke. It looks like the correct part that will is 12342801 . The original looks like the image on top with two circular cutouts in the mount, while the new mount on the bottom has a single deep rectangular cutout

 

[jkcondrey]

Flashoffroad has several articles on this exact process. Check them out. I vaguely recall the yoke deal on one article, mentioned using a beam torque wrench to note the break point on torque when removing the yoke to give you the torque yield for reapplying the correct yoke. Not a click type torque wrench.

Been doing a bit more research. It looks like I may be able to frankenstein the front drive shaft by putting in later front section which has the 4" ujoint rather than the 3.5" ujoint. It wouldn't be bad idea to replace drive shaft carrier assembly which looks pretty ugly. It looks like people have the rear part of this shaft as part of an a2 drive train conversion. Can anyone confirm I can mix and match front and rear portions of the front drive shaft?