8 3/4" 3rd member re-gear/rebuild

Do it myself or take it to a shop?

  • Save yourself $80-100

    Votes: 2 28.6%

  • Don't go insane and have to wait 3 weeks to finish all the work and possibly ruin it

    Votes: 5 71.4%
  • Total voters
    7
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MopaR&D

MopaR&D

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The 8 3/4" in my Duster currently has 2.94 gears and a worn-out clutch-type Sure Grip diff in a 741 case. I got a 489 case with 2.76 gears and open diff which I intend to swap over the Sure Grip unit into (after new clutches) as well as a 3.55 ring and pinion. I got the full kit, gears, and SG clutches from Dr. Diff including a crush-sleeve eliminator.

Now I'm wondering if I should attempt to fully assemble everything myself or take it to a drivetrain shop to have it done; I've done 3 ring and pinion swaps so far (one in a Ford 8.8 and two Mopar 8 1/4" units) and unless I got really lucky with the pinion depth shims it was a royal pain in the @$$ to get set up correctly. The Dr. Diff site said the ring and pinion were made by Richmond so I'm thinking I need to properly measure pinion depth which I don't have the tools for. Regardless I'll be rebuilding the SG unit, installing the pinion bearing races and ring gear onto the diff carrier myself.

Note the main reason I'm leaning to take it to a shop is the Duster will not be driveable the whole time I'm doing this as I need to remove the pumpkin that's in it now to grab the SG unit.
 
Well your going to need a set up bearing, either buy one or make one. Without a pinion depth gauge, your going to be doing a lot of trial and error. Plus you'll need a dial indicator to set the back lash. I think I would farm it out.
 
Some shops have no warranty at all if they do not do all the work.

I pay to have mine done, I just source the parts.
 
Aren't you and engineer? If you didn't do it, I'd be disappointed in you.

I've done a Dana 60 as a dumb college student and it turned out great. The 8-3/4 is a walk in the park. DO IT!
 
mopowers said:
Aren't you and engineer? If you didn't do it, I'd be disappointed in you.

I've done a Dana 60 as a dumb college student and it turned out great. The 8-3/4 is a walk in the park. DO IT!
Click to expand...

lol sort of I'm currently a grad student. I could probably get the pinion bearing pressed off the 2.76:1 piece and use that to check the pinion depth, and not having a crush sleeve to deal with would be nice. The past few I did were with used or new OEM gear sets so I got lucky with just reusing the same shims on the "new" pinion shaft.

It's just a lot of work especially if I have to remove and reinstall the pinion multiple times to get a good gear contact pattern. If I knew I could put it all together in one shot I'd definitely do it myself. IDK I'll get in touch with the shop and work out the details, it's still up in the air.
 
Sounds like you've already made up your mind. If the time it would take you is worth more than what you'll pay someone to do it for you, take it in.
 
Just curious. Anyone know what a shop gets for a gear change and set-up for 8.75? Talking about labor only handing them the pig and parts.
 
Like roy said in post #2, (which i just did ) unless you can get the pinion brg off without destroying it or buy a new one. For around 20 bucks you can get a 80 grit ball hone , took me 10 mins to hone mine get a shim and go to town.
 
I finally got around to calling a local driveline shop, looks like it'll be at least $250 just to get the gears set up and price goes up from there for more assembly etc. Guess i'll take a stab at it myself, first I need to figure out how to get the old pinion bearing off without damaging it.

I wish I had a pinion depth gauge dammit
 
MopaR&D said:
I finally got around to calling a local driveline shop, looks like it'll be at least $250 just to get the gears set up and price goes up from there for more assembly etc. Guess i'll take a stab at it myself, first I need to figure out how to get the old pinion bearing off without damaging it.

I wish I had a pinion depth gauge dammit
Click to expand...

If it makes you feel any better about doing it yourself, a local shop did a buddies rear gears 3 times before they didn't blow up within a week.
Surely we can do better than that.:D
After the first set blew up I told him to find another assembler, but nooooo.
 
TrailBeast said:
If it makes you feel any better about doing it yourself, a local shop did a buddies rear gears 3 times before they didn't blow up within a week.
Surely we can do better than that.:D
After the first set blew up I told him to find another assembler, but nooooo.
Click to expand...

Isn't that a definition of stupidity, doing something over and over again and expecting a different result? Lol

I found these little things on Summit, anyone try one? The reviews all look pretty good...
Ratech Pinion Depth Setting Tools 10007
 
You don't need a depth tool. Just hone out an old bearing to use as a setup bearing. You can totally do it. When you start moving the ring gear carrier around with the side adjusters, make sure the last way they turn before you button them up is in.
 
last time I even asked was $200 and that was 17 years ago. I made said set up bearing. Took an HF surface prep kit (3 grades of scotchbrite buffs and a die grinder collet) and just polished the inside of the good old bearing until it slid on. That metal is hard so it took about 20 minutes with the gnarliest media. make sure you cool it off as it will get hot and the heat will actually expand it, so test fit it after you quench it. slides on nice and neat, no binding. Now I can set it up with shims, measure it and add/subtract shims easily until I get my pattern. remember to put a torque on the pinion nut to get the right pattern.
 
Last edited:
mopowers said:
You don't need a depth tool. Just hone out an old bearing to use as a setup bearing. You can totally do it. When you start moving the ring gear carrier around with the side adjusters, make sure the last way they turn before you button them up is in.
Click to expand...

I know I don't need a depth tool but it would make things much faster. I've done gear swaps before but it was with OE used gears so you could read the number on the pinion head and just swap shims to make the difference and it was a "once and done" deal, got the pinion depth right on the first try. I think I'll give the Ratech tool a shot, it's only $30 and the more I've read up on how to use it the more I like it. I've seen discussions (arguments lol) on here about how measuring pinion depth off the carrier bearing cap mating surface is inaccurate, well this tool actually goes off the bearing saddle itself. You place it on top of the pinion head and measure the distance between the tab and bottom of the bearing saddle and compare that to a set value and the depth number written on the new pinion from the manufacturer.

I definitely won't be getting one of the cheap pinion depth measurement kits (Proform, etc.), reviews about those are horrible. And the only other option is the $400+ kit from T&D Machine, no thanks.

Tomorrow I'll probably hit up Harbor Freight for a bearing separator tool for my Harbor Freight hydraulic press lol
 
MopaR&D said:
I know I don't need a depth tool but it would make things much faster. I've done gear swaps before but it was with OE used gears so you could read the number on the pinion head and just swap shims to make the difference and it was a "once and done" deal, got the pinion depth right on the first try. I think I'll give the Ratech tool a shot, it's only $30 and the more I've read up on how to use it the more I like it. I've seen discussions (arguments lol) on here about how measuring pinion depth off the carrier bearing cap mating surface is inaccurate, well this tool actually goes off the bearing saddle itself. You place it on top of the pinion head and measure the distance between the tab and bottom of the bearing saddle and compare that to a set value and the depth number written on the new pinion from the manufacturer.

I definitely won't be getting one of the cheap pinion depth measurement kits (Proform, etc.), reviews about those are horrible. And the only other option is the $400+ kit from T&D Machine, no thanks.

Tomorrow I'll probably hit up Harbor Freight for a bearing separator tool for my Harbor Freight hydraulic press lol
Click to expand...

Sounds like you're well on your way. On the bearing splitter - you may have to grind the edge of the two halves to get under the bearing more easily. I know I had to on mine. Let us know how it all works out!
 
MopaR&D said:
I know I don't need a depth tool but it would make things much faster. I've done gear swaps before but it was with OE used gears so you could read the number on the pinion head and just swap shims to make the difference and it was a "once and done" deal, got the pinion depth right on the first try. I think I'll give the Ratech tool a shot, it's only $30 and the more I've read up on how to use it the more I like it. I've seen discussions (arguments lol) on here about how measuring pinion depth off the carrier bearing cap mating surface is inaccurate, well this tool actually goes off the bearing saddle itself. You place it on top of the pinion head and measure the distance between the tab and bottom of the bearing saddle and compare that to a set value and the depth number written on the new pinion from the manufacturer.

I definitely won't be getting one of the cheap pinion depth measurement kits (Proform, etc.), reviews about those are horrible. And the only other option is the $400+ kit from T&D Machine, no thanks.

Tomorrow I'll probably hit up Harbor Freight for a bearing separator tool for my Harbor Freight hydraulic press lol
Click to expand...

mopowers said:
Sounds like you're well on your way. On the bearing splitter - you may have to grind the edge of the two halves to get under the bearing more easily. I know I had to on mine. Let us know how it all works out!
Click to expand...

You also have to be careful about chipping the back side of the pinion gear teeth with those splitters if you tighten them up too much.
If I wasn't trying to save the bearing I used to cut the cage off and use an oxy/acet torch and heat one small spot in the center of the inner race red and smack it a couple of times with a punch.
They would slide right off after.
 
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