8 3/4" sure-grip swap and rebuild questions

[MopaR&D]

I know this stuff has been covered before but the other threads I found didn't exactly answer my specific questions. I bought a 3.55:1 ring and pinion from Dr. Diff along with a clutch kit for my Dana Powr-Lok diff. My Duster has been running a 1967 741-case with sure-grip and 2.94 gears. I got a 489 case from my cousin when he scrapped his '72 Polara. Plan is to rebuild the sure-grip and swap it into the 489 case with the 3.55:1 gears, I will then take the open diff from the 489 case and swap that back into the 741 case with the 2.94 gears so I ultimately have 2 center sections (one 2.94 open, the other 3.55 SG).

So far I've rebuilt the sure-grip unit with the new clutches. I didn't put straight friction additive during assembly though as I wanted to save as much as possible to put into the housing after final assembly; I poured about a tablespoon of additive into a small tupperware and then poured in about 3-4 tablespoons of gear oil and mixed it around. I coated all the clutch plates with this mixture during assembly. I then torqued the LHT diff bolts to 45 lb-ft which I heard mentioned in a YT video (hell of a time finding that torque spec), tricky because I don't have a fixture (might have been a bit closer to 48-50 lb-ft as I was using a beam-type torque wrench) and I just clamped an edge of the ring gear flange into a vise with some old bed sheet material to keep it from getting marred. Is it a big deal if the bolt torque is a little over? Also just saw another thread where someone said to torque them to 40 lb-ft... which is it? The bolts were still oily and I didn't put any thread locker on them.

Next questions, do I need a fixture to torque the ring gear bolts? And is putting thread locker on those crucial? Saw some posts claiming yes vs no so not sure how important it is. I have a vise at home but haven't yet mounted it in my garage and I have doubts about the jaws being wide and deep enough to clamp on the diff carrier to hold it in place while I torque the ring gear bolts.

Also the 489 case is getting new pinion bearings but the carrier bearings on the sure-grip seem to be in great shape. I know the "right way" is to replace the carrier bearings too but is it that big of a deal? I did make sure to keep the races with their respective cones and not mix them up.

Lastly, is that special spanner tool for adjusting carrier backlash necessary? I figured I could just rig something up or carefully tap the adjusters with a driver of some sort to turn them and adjust the carrier bearings. But thinking about it more I imagine the bearings need some sort of preload once the correct backlash is set?

Was really hoping to get this all mostly done this coming weekend but that won't be the "case" (tee hee) if I need to order that spanner tool.

EDIT: I do have a FSM for my Duster but it's 1970 model year and covers the cone-type sure-grip not the clutch-type like I have...

 

[413]

Make life easy and get a spanner tool.

move past the hammer and screwdriver days.

 

[MopaR&D]

Make life easy and get a spanner tool.

move past the hammer and screwdriver days.

But the hammer and screwdriver will work, right? Hard to say when I'll be doing this all again and if I order the tool now it probably won't arrive until next week. I've already had my Duster down for almost a month because I've had to spend the last 3 weekends helping my parents move and I just wanna get this **** done ASAP lol. Not to mention $10 shipping on a $35 part...

I'll do it if y'all think it's worth the cost and wait though.

 

[Bad Sport]

I'll do it if y'all think it's worth the cost and wait though.

Make one. I used a piece of 3/4 square tubing, marked and drilled the spots where it lines up with the holes and put bolts in there with a nut on the other side. You will need a dial indicator to set backlash, you'll also need it when you install the axles to set end play.

As far as the carrier bearings I "think" they are a different size from 741 to 489, someone correct me if I am wrong.

 

[MopaR&D]

Make one. I used a piece of 3/4 square tubing, marked and drilled the spots where it lines up with the holes and put bolts in there with a nut on the other side. You will need a dial indicator to set backlash, you'll also need it when you install the axles to set end play.

As far as the carrier bearings I "think" they are a different size from 741 to 489, someone correct me if I am wrong.

That's pretty clever, I was wondering if I could just make a tool, it's simple enough. Saves me time AND money and I love making things like that.

The carrier bearings are different from 741 to 489 but it's only the ID of the inner race where it presses onto the carrier. Keeping all the races and cones together they will swap from one to the other.


Still looking for answers to my other questions though...

 

[Lefty71]

Make life easy and get a spanner tool.

move past the hammer and screwdrive

Agree with this 110 percent.. You can not get a feel for what you are doing (spreading the case) with a hammer and screwdriver. Even if it's homemade, it will be sweet.

I think you could get by without locktite, but why?? Along those lines, you can hold the gear pretty easily, since the bolts don't get torqued super tight anyway.... just be careful of what you are doing.

 

[MopaR&D]

Agree with this 110 percent.. You can not get a feel for what you are doing (spreading the case) with a hammer and screwdriver. Even if it's homemade, it will be sweet.

I think you could get by without locktite, but why?? Along those lines, you can hold the gear pretty easily, since the bolts don't get torqued super tight anyway.... just be careful of what you are doing.

Hold what exactly? 55 lb-ft is a decent amount, no way I could just bear-hug the diff and torque the bolts if that's what you mean? I'll go ahead and use some blue loctite on the ring gear bolts since I already have some and I guess it can't hurt. The sure-grip diff is already bolted together and torqued though without loctite and I'd much rather not take it apart again just to do that.

I had a hard time keeping the diff from wanting to rotate out of the vise jaws while torqueing the diff bolts and that was 45 lb-ft. I can't grab on to that flange with a vise again for doing the ring gear because... well that's where the ring gear goes lol.

 

[Lefty71]

Hold what exactly? 55 lb-ft is a decent amount, no way I could just bear-hug the diff and torque the bolts if

Why not put it in the pumpkin first?? Meaning the diff case. Then you can just use a screwdriver or similar against the next bolt down the line or whatever to keep it from spinning, or you can bearhug the whole thing lol.

 

[MopaR&D]

Why not put it in the pumpkin first?? Meaning the diff case. Then you can just use a screwdriver or similar against the next bolt down the line or whatever to keep it from spinning, or you can bearhug the whole thing lol.

Ah I see what you mean now lol. Idk I'd be afraid of the ring gear not seating properly on the diff. I'd also need to assemble the pinion first which I'd rather do after the ring gear and diff are done. Your method makes sense but seems like... not the right way lol I've never heard of someone doing that way

 

[AJ/FormS]

I grabbed an old axle and cut off about a foot, then welded on a big old hex nut.
I clamp the nut in the vise and slide the splined end up into the clutches.
After that you can torque the bolts no problem.
I never use loc-tite on these bolts. The torque spec is for lightly oiled threads, not for loc-tite.
My 1969FSM lists the torque at 55 ftlbs.

 

[Lefty71]

Ah I see what you mean now lol. Idk I'd be afraid of the ring gear not seating properly on the diff. I'd also need to assemble the pinion first which I'd rather do after the ring gear and diff are done

The ring gear should have been warmed up and set on the carrier with alignment pins, then snug the bolts....it should be pretty much where it's going to be by then.....you're going to have a hard time putting the pinion in after the ring gear and diff are done.

 

[Jadaharabi]

If you do not have the clutch disc in the carrier lined up I definitely would not be tightening those left hand thread bolts. Did you slide an axle in to line them up and tighten the bolts with the axle still inside the differential or did you just tighten the bolts?

 

[MopaR&D]

I grabbed an old axle and cut off about a foot, then welded on a big old hex nut.
I clamp the nut in the vise and slide the splined end up into the clutches.
After that you can torque the bolts no problem.
I never use loc-tite on these bolts. The torque spec is for lightly oiled threads, not for loc-tite.
My 1969FSM lists the torque at 55 ftlbs.

Another clever idea, you guys are the best lol... I don't have an old axle to cut up but that got me thinking I can do something similar with one of the axles I do have. I'll put my spare tire facing down on the ground and put the lugs on the flange end through the lug holes in the wheel (probably snug them down with a couple lug nuts to keep it steady) then use that contraption like a fixture and slide the splines up into the diff to hold it still. @Lefty71 you're right the ring gear should be seated first if that's all done correctly but I think I'll use this method to torque the bolts instead. Lol and by "assemble the diff first" I meant have the diff and ring gear bolts torqued before putting it in the case.

If you do not have the clutch disc in the carrier lined up I definitely would not be tightening those left hand thread bolts. Did you slide an axle in to line them up and tighten the bolts with the axle still inside the differential or did you just tighten the bolts?

I did make sure to line up the clutch disc splines on both sides with an axle shaft before snugging down the bolts. I ran them down about 90% of the way in my garage then took the diff over to my local CreatorSpace to use one of their vises for the final torqueing. Good catch though I need to check and make sure the splines are still lined up before I continue assembly as I didn't torque the bolts with an axle still inside.


Just a note I have done 3 rear-end gear swaps/rebuilds in the past but it was a Ford 8.8" and 2 separate 8 1/4" rears so I understand the basics. This is my first 8 3/4" gear swap though. Sure is nice not having to be under the vehicle the whole time or have the entire rear axle assembly removed, that'll be great when it's time to set the gear mesh for the ring and pinion.

 

[MopaR&D]

Ok so I got this thing pretty much done although someone pointed out my contact pattern should be biased toward the toe side, what do you guys think? I used a honed-out pinion bearing to get the depth right and thought it was good so it's assembled now with the "real" inner bearing pressed on, really not trying to pull that thing off unless it's absolutely necessary. Backlash is at .007" so I could adjust that a bit but that's pretty much all I'm willing to do at this point.

Also I take back what I said about this being easier than a non-banjo axle lmao this freaking sucks without having a fixture and a decent proper steel workbench.

 

[MopaR&D]

I guess I'll take that as a "don't worry about it"? lol... well I did have to redo the backlash as it turns out it tends to move about .002" after the carrier bearing cap bolts are fully torqued. I thought BL was .007" in those pics but it was actually closer to .010", tightened it up so now it's at .006" with the caps torqued and now the pattern on the drive teeth is a bit better; still sliiightly offset towards the heel but I'm so over this thing, as of last night it's bolted into the axle housing and axle shafts are installed. Just need to set axle end play, fill it up with gear oil (+additive), put the wheels back on and adjust the rear drums a tad then it'll be ready to test drive.

I'm pretty excited, the entire time I've had this car it's had 2.76 or 2.94 gears. Aside from the time I borrowed a center section with 4.10 gears for a couple months and that sucked I couldn't drive the car anywhere over 60 mph.

 

[MopaR&D]

Well it whines, obviously I'm not very happy about it. I'm hoping it might just be that the pinion nut isn't tight enough (I didn't torque it properly) and/or the bearing races weren't fully seated when I installed them. It started out only whining on coast from what I could tell but when I gave it some gas it seemed to start to whine on acceleration too. If it ends up being that the pinion depth is off I'm gonna cry lmao.

I don't get it the mesh pattern looked great why does this thing have to break my balls like this...

 

[john-9]

your pattern is favoring the heel part of the gear on the drive side , not the best as under load the gear will walk even higher off the ring gear ,,add another .003 at a time to the pinion shim to bring the pattern down check the pattern again add more shim if necessary ,,i read all the posts and did not see any mention of what you set the preload at on the pinion bearings , should be 20-25 in/lbs for new bearings . pull it back out before you ruin the gear set , check that you seated the pinion races completely and readjust your pattern and get proper preload on the pinion bearings.

 

[MopaR&D]

Pinion preload was at 25 in-lbs. I'm gonna have to warm up to shimming the pinion as right now I feel like pushing the car off a cliff lol. The timing of all this sucks as it's just starting to get down near freezing temps at night and the sun is almost set by 6:00 pm.

I hammered the races in pretty hard (with the proper driver tool of course) and ran my fingernail around the undersides to check for any gaps on the seating surface and they felt like they were in all the way. I just remember back when I did a R&P swap in my Jeep years ago it whined pretty badly and I took it to a shop but it turned out all they needed to do was torque down the pinion nut as it either backed off or the races weren't fully seated, ran perfectly after that but I probably won't be as lucky this time.

I guess today after work I'll run and pick up a torque wrench that can go past 250 lb-ft and check the pinion nut although at this point it sounds like that's not likely the problem (I wish). When I had the pumpkin on my "bench" (folding plastic table with a metal drip pan on top) I torqued the pinion to 150 lb-ft using a yoke-holding tool then carefully zapped it with my 1/2-inch Milwaukee impact until the nut didn't seem to turn anymore.

I'm definitely not doing any diff/ring+pinion work again until I have a big steel workbench, fixture to hold the 3rd member and bigger garage with decent lighting. Working on cars in general is pretty friggin awful if you don't have a comfortable workspace.

 

[mderoy340]

With the 489 case are you using a crush sleeve or crush sleeve eliminator? If you are using the crush sleeve and hit the pinion nut with an impact you need to get a FSM and start over.
Also agree you need to add more shim and get the pattern moved to the toe.

 

[MopaR&D]

With the 489 case are you using a crush sleeve or crush sleeve eliminator? If you are using the crush sleeve and hit the pinion nut with an impact you need to get a FSM and start over.
Also agree you need to add more shim and get the pattern moved to the toe.

Yes it has a crush sleeve eliminator kit. I'll need to check the pinion depth shims I got again because I don't remember there being a 0.018" one, right now it has a 0.015" shim plus the 0.020" shim.

I'm guessing the inner bearing will be ruined and I'll need to buy another one when I press it off even if I use my bearing puller tool? It's the kind that has 2 halves you tighten together under the bearing then press the pinion shaft down through.

EDIT: I do also have a 1970 Plymouth FSM I've been referring to

 

[mderoy340]

Yes it has a crush sleeve eliminator kit. I'll need to check the pinion depth shims I got again because I don't remember there being a 0.018" one, right now it has a 0.015" shim plus the 0.020" shim.

I'm guessing the inner bearing will be ruined and I'll need to buy another one when I press it off even if I use my bearing puller tool? It's the kind that has 2 halves you tighten together under the bearing then press the pinion shaft down through.

EDIT: I do also have a 1970 Plymouth FSM I've been referring to

You should have some .010, .012 and .013s you can stack up.

 

[my68barracuda]

Pinion preload was at 25 in-lbs. I'm gonna have to warm up to shimming the pinion as right now I feel like pushing the car off a cliff lol. The timing of all this sucks as it's just starting to get down near freezing temps at night and the sun is almost set by 6:00 pm.

I hammered the races in pretty hard (with the proper driver tool of course) and ran my fingernail around the undersides to check for any gaps on the seating surface and they felt like they were in all the way. I just remember back when I did a R&P swap in my Jeep years ago it whined pretty badly and I took it to a shop but it turned out all they needed to do was torque down the pinion nut as it either backed off or the races weren't fully seated, ran perfectly after that but I probably won't be as lucky this time.

I guess today after work I'll run and pick up a torque wrench that can go past 250 lb-ft and check the pinion nut although at this point it sounds like that's not likely the problem (I wish). When I had the pumpkin on my "bench" (folding plastic table with a metal drip pan on top) I torqued the pinion to 150 lb-ft using a yoke-holding tool then carefully zapped it with my 1/2-inch Milwaukee impact until the nut didn't seem to turn anymore.

I'm definitely not doing any diff/ring+pinion work again until I have a big steel workbench, fixture to hold the 3rd member and bigger garage with decent lighting. Working on cars in general is pretty friggin awful if you don't have a comfortable workspace.

I used a couple of scrap pieces of angle iron to attach the third member to my engine rollover.
Simple and cheap and works great.
I will see if I can find a photo.

 

[MopaR&D]

Well I measured the thicknesses of the pinion depth shims I have, all I got were increments of .005". There are three .010", a .015" and a .020". Currently the .020" and .015" are in there so I could swap the .015" for two .010" to bump it up to .040" total thickness but if it needs to be changed a smaller amount I need to get more shims. I'm having trouble finding a set as the ones I'm finding don't list any dimensions; ID, OD or thickness they just say "for Chrysler 8.75" or whatever. I may just order some from McMaster-Carr based off the specific dimensions needed unless you guys know what I need?

 

[MopaR&D]

Still no luck in finding a shim kit with actual specs... I just placed a McMaster order for a 10-pack of 0.003" carbon steel shims, expected to arrive Friday. ID is a hair bigger and OD is about 1/8" bigger but that shouldn't matter.

 

[92b]

For what its worth. This is what I use. It can rotate 360 degrees and has a bolt to lock it down to any position. It has a 9" in it now but a 8 3/4" will also fit. The fixture can be pulled out when not in use.