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Discussion Starter · #1 ·
I am trying to figure out what the specs are for setting up our diffs (backlash, tq specs, etc). I have a FSM for a 99 Trooper, but I'm not sure if the modified 12 bolt would be the same as setting up a regular 12. If anyone has a 89-97 Trooper FSM that they'd be willing to host/send me, I'd appreciate it. I'd be happy with just the diff section to save you time uploading/space.
 

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The pinion depth is set via the scribed numbers measuring from the back cover sealing surface to the end of the pinion. I usualy just go by the factory shim behind the large pinion bearing. Some can have shims behind the large pinion cone/race also. Once that is set you load the front yoke end with the crush sleeve followed by the small pinion bearing. You then have to install the seal followed by the yoke and nut. Ive used air guns to start crushing the crush sleeve, I've also taken a big pipe wrench and held the yoke and turn the nut by hand. I take it down to zero lash and preload the bearings that makes for roughly 5 -7 lbs of turning resistance. I prelube the bearing with a lite grease. Back lash is in general about 4- 7 thou. Depending on a brand new or used set. I like to set them tight. You have to adjust backlash by shimming behind the carrier bearings.

I sometimes will cheat and shim behind the carrier race. If there is a large factory washer/shim it makes it easy to place paper thin shims behind them and insert the carrier with the big washers loaded already. You want a snug fit on insertion of the carrier that's the preload on the carrier bearings. It takes a couple test fits to make sure the back lash is adequate. Then you finish torque the cap bolts to roughly 45 ft lbs

A normal 44 doesn't have a crush sleeve so you set the pinion bearing preload via with shims...
 

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Discussion Starter · #3 ·
Thanks, I know how to set the backlash though. In the FSM it says 10 bolt and modified 12 bolt backlash should be .005-.007, so we're good there. The cap bolts it says should be 72ftlbs on the 10 and 80 on the modified 12. The ring gear bolts to the carrier though, I'm not sure about. The FSM says 80ftlbs for the 10 bolt, but 130ftlbs for the modified 12. I don't know if I should go that high on the regular 12 bolt. New bearings should be 5.6-9.9lbs preload. I just really want to make sure I don't destroy this gear set, but I think those specs should be alright.
 

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That's crazy high for the ring gear bolts !!! If there around the 3/8 size I wouldn't want to go more than 45-50 ft lbs. There's what 8 or 10 bolts all around. I would stick with a standard rating chart for bolt size torque. I can see the 80 but 130 is pritty dam high. To me when a bolt is at it's max like that the shock of dropping the clutch could pop the bolt ....
 

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Discussion Starter · #5 ·
My thoughts exactly. There are 12 bolts on the rear, 10 on the front. I might just do 80ftlbs on the rear too, think that should be sufficient with some loctite. Only other spec I can really find is the ring gear run out, .001-.002in. That was for the 10 bolt, bet the 12 is the same. If there's anything else important, let me know.
 

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As you rotate the ring and pinion around you can get a little bit of variation (tighter clearances) just look for that when you set the backlash and go off the tightest spot clearance wise for the final reading/setting. I forgot about that fact. Good job !!! Usualy that shows up in a brand new set. Also for break in drive easy so the gears polish together. I've heard like 500 miles... I would think 200-250..... I like to do a quick drive say 2-3 miles gets everything warmed up and then park it and let it cool down.
 

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Discussion Starter · #7 ·
Thank you for the advice bradzuzu. These gears are used, I am just installing lockers and then reinstalling them. I confirmed today that the 12 bolt ring gear torque specs are 80ftlbs. I hope this thread helps anyone out there looking for how to set up their gears, I know I could not find anything technical when I searched.
 

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No problem !!! I had to squeeze the brain a few times to requrditate some of that :)....
I priced a locker yesterday $475 pluss shipping !! Gizmo sent me the part number..
How's that price compare ??? The last 44 I did was for my front axle and it was a gear swap from 3:08's to 4:10's plus a track lock (lsd)third member. For the most part it all dropped right in.
 

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Discussion Starter · #9 ·
What kind of locker is that? I got a 10 bolt Aussie for $365 off Indy4x on ebay, and a 12 bolt ARB 2nd hand but NIB for $625 with all new bearings. These are both going into a set of 4.77 third members.
 

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Mine is a Powertrax No-Slip 92-0444-3020 which is for the LSD carrier.
Thank you Gizmo !!!
It would be a week out through( six states distributors)
 
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