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Definitive order for setting a 10 bolt ring and pinion

10K views 73 replies 7 participants last post by  AutoGear 
#1 ·
Hi all,

I'm wanting to learn how to do the rear gears on my '91 Camaro. I hear a lot of talk about doing this is hard work and that it's not easy, but then I like a challenge, I have access to an engineering workshop (I'm an engineer) and reckon that I can give this a go. The only thing I'm confused on is the order of rebuilding the axle back up, and I'm seeing conflicting advice.

I'm replacing my stock 3.08:1 open diff with an Eaton Trutrac and Motive Gears 3.73:1, so I'm going from a series 2 to series 3 carrier. I have bought a Richmond rebuild kit that comes with a complete set of Timken bearings and seals. I will be replacing all the bearings and seals throughout the axle as well as thoroughly cleaning and repainting it.

What I'd like to know, apart from the definitive order for reinstalling and setting up the gears, is where do you start with estimating the pinion shim? I've heard that people use a 'setting' pinion bearing with has a slightly increased ID to help make it easier installing it and taking it off. Is this a good idea?

Cheers for your help, I will keep this updated once I get started, as yet I have put the car in storage and am waiting to get around to hauling the axle out.
 
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#2 ·
Setting the pinion depth is the hardest part of setting up a set of gears. Start with the pinion shim that was installed on the original gear. That will get you close enough to get a readable pattern. Don't install the crush spacer until the final assembly, and use the old pinion nut for all trail assemblies. You must set the pinion bearing preload correctly each time you do a trial assembly. Don't use a slip on bearing.

I'd recommend getting a Yukon differential shim set from Summit or Randy's Ring & Pinion. The shims in the Richmond kit suck.

Be sure that you adjust the backlash and get the differential bearing preload tight for each trial assembly. Get the bearings tight enough that you can just pull the differential out by hand. On the final assembly you want it tight enough that you can not pull it out by hand. Post pictures of the contact pattern for us to see if you don't know how to read it. We can guide you in the right direction from what the pattern says.
 
#3 ·
When setting the pinion depth and you say set the pinion preload, what figure would you recommend and is that with the ring gear engaged or spinning freely?

How do you remove the pinion bearing 'easily' or without damaging it? Have any tips on that?
 
#5 ·
Was a bit of a delay on getting the work started on my axle, had to wait for the workshop to become free, but finally got it out and back to my work (have far more tools and machines + it is heated.)



Cover off, 3.08 gears and open carrier:



Carrier, pinion and all bearing races removed. Thoroughly cleaned with brake cleaner. Also removed the fairly large burr from where the axle tube bore had been machined into the centre pumpkin casting. Nice GM quality control there!



Carrier, both shims were measured and marked, along with the carrier bearing clamps.



In removing the drum brake backing plates from the axle, I had to muller the huge bolt that anchors the drum brake springs. Turns out these are out of production and no longer able to be purchased, guess I'll have to make my own!





Next problem was to suss out how to remove the pinion bearing for setting the pinion depth. Would need to be able to remove the bearing several times without destroying it. Would be nice to get my hands on the Yukon clamshell design thing, but unfortunately they cost a fortune, so again, time to make up my own!















Now the pinion and bearing are apart, I've measured up the shim, turns out to be .031".

Now waiting for the Axle casing to come back from the shot blasters and being powder coated. Then the rebuild can begin!
 
#7 ·
FYI - you can buy the brake anchor bolt that you 'mullered'. 2 weeks ago I grabbed a new set of backing plates that came with the anchors from Advanced Auto. I needed the backing plates anyway - maybe you don't, but they were less than $20 a piece.

I know BGH recommended to not use a 'slip-on' bearing, but I do. But, by 'slip-on' I mean I still need a press to get it on and bearing seperator and press to get it off. I clean off .001-.002" of the bearing to accomplish that. I use the same brand bearing to slip-on that is in the kit I'm using. FWIW, I have slip-on inner pinion bearings for all 3 GM 7.5's, one for an 8.5, and one for an 8.8. I've never had an issue when the final bearing is installed in terms of the setup changing.

That is a nifty bearing seperator that you made, but you can purchase a good one $50-80 that will work with more than one bearing size. I always use a press instead of a T-bar puller so as to not beat up the bearing nor the pinion - just my preference. Also, I don't have access to the machining apparatus that you have.
 
#8 ·
Hi all,

Thanks for the kind words, been in the the engineering game since I was 16 and now 27 I like to think I'm starting to get good at it!

I wish it was that easy to get those parts and the pullers over here! Unfortunately in the UK the local bearing stockist who normally has everything under the sun wanted over £50 for just the race of the larger pinion bearing and around £75 for the actual roller bearing section. Thanks to Rockauto getting a second bearing (just in case) one cost around £15 shipped.

I have a question, I'm about to start the rebuild, as I've just received the case back from the powder coaters. Can I use the stock shim that I removed from the original pinion or should I make a new one up to match from the new shim pack?

My original shim measures up at .031" so was going to start with this size anyway, it is just a case of whether its with the old one, or with a new one?

Also, I have these specs for all the bits, if someone can just confirm or correct them:

Ring Gear bolt torque: 65ftlbs
Carrier Cap bolt torque: 55-60ftlbs
Backlash: .006" - .010"
Pinion Preload: 12 - 15in lbs (I've read on here is should be more like 20in lbs)

Cheers!
 
#9 ·
You can use the original shim or use new shims from your kit. It doesn't really matter. It's just a starting point.

All of your specs should be fine. I usually go a little bit tighter than that on the bearing preload, but what you have should be fine. If you read a factory repair manual I think it says something like 35 inch pounds of preload. I would never go that tight.

What mill did you use to make that tool? I use a Hurco, Sharp, Prototrak and a Republic Lagun at work.
 
#10 ·
Hi BGH,

I made that on our Bridgeport VMC800. Quite a relic now, definitely no competition against the newer stuff but does still hold its tolerances fine and does a good job!

The other VMC I run is a Haas Minimill, not a patch on the Heidenhain control that the Bridgeport has, but a cheap and cheerful mill all the same. I mainly run our production lathes. Up until last week there were two of us running the shop, but sadly my mentor and foreman who taught me all I know died. Real shame as one of his first jobs was setting up gears similar to this on old style paper mill machines. He was looking forward to helping me out with the install.

Now waiting on some tools to come through from the supplier, having been told by my dad that he had an inch pounds beam style torque wrench from when he used to set up his Mustangs axle, I went to go get it to find out it was actually a foot pounds torque wrench. That should be here Friday, so until then I'm just going to be getting everything ready for this weekend.

BGH - is it ok if I post up some photos of gear patterns for your review? I have an good idea of what I'm looking for, but would like an expert opinion at the same time.
 
#18 ·
Ok, changed out the shim, going from .032" to .030".

Had a nightmare trying to get the pinion back out, the outer bearing was well and truly stuck on the shaft. The only way I managed to get it out was with a copper mallet and several heavy blows. The reason I say this is putting it all back in and resetting the preload, the pinion now feels notchy. I honestly can't remember if it felt like this the first time round, but I don't know if this is normal.

Either way, set the carrier back in, still only reading .006" on backlash I achieved this:



 
#19 ·
Pinion depth looks great.

You might have damaged the outer bearing or race. Do you have gear oil on the bearings? They will feel notchy if they are dry. I usually sand the pinion shaft smooth to remove all of the black surface finish from the heat treat process. This makes the bearing slide on and off a little easier. I also put some oil on the shaft.
 
#20 ·
Would you recommend me trying to get the backlash a bit bigger than just on the bottom. I'm a middle tolerance kinda guy, would prefer it to be loose than tighter.

Hmm, I think seeing as I want to do this right, and do it right first time, I'll order a new bearing and race. I have been using gear oil, and after the agro of getting it out the first time, I put the pinion up in a lathe and rubbed down the finish. Also put some grease on there this time.

When I put it back together the first time and it felt notchy, I stripped it out again to check the bearings and it came out a lot easier, but definitely not as loose as the stock one was, it pretty much feel out once I got the yoke off.
 
#21 ·
You don't want the bearing to slide on easy. You want it to fit tight, but not so tight that you damage it like this one. You should have to tap it out, but not hard.

As for the backlash, you can try opening it up some, but watch your pattern. If it moves toward the heel of the tooth then you might want to put it back where it is now. Usually tight backlash moves the pattern to the toe and loose moves it to the heel. Right now your drive side is slightly offset to the heel. Heel to toe actually looked better with the thicker pinion shim, but it was favoring the root a little.
 
#23 ·
I think I actually liked it better with the .032 shim. I think the drive pattern moved too far to the heel with the .030 shim. I think when you open up the backlash a little more it's going to get worse, but I would like to see it with more backlash before you do anything to the pinion again. I'd also like to know what Imsport thinks about it.
 
#24 ·
The contact patch was wider with the first shim, but centered better face to flank with the second. Thats kind of subjective as the patch will vary with the amount of force imparted when turning. You might try the first shim with a little more BL and see what results.
I think you'd be OK with either. Maybe split the diff and go. The BL is going to bump up a couple thousandths after break in.
 
#25 ·
Ok guys, really appreciate your input, as right now I'm scratching my head a bit and thinking this shouldn't have done what it has, but hey ho, the mystery of gears!

What I shall do then is try for a little more backlash and see what the pattern comes out with, like you say BGH, I can understand that more BL will make the contact pattern move out to the heel.

I'll get some photos of that and then see what you guys think. But If I can get the BL a bit higher and whack the .032 shim back in it might correct it a bit more.

I'm on hold waiting for more new outer bearing and race to arrive. They should be here Tuesday, then play will resume and on to the fun of doing the build for real! :D
 
#26 ·
Still waiting on the new outer bearing to show up, but thought I'd see what I could get with opening the backlash out. Managed to get a nice .009" reading on the clock, and with this I ran the following pattern:

Drive:


Coast:


Now from that the drive pattern appears to be too far out towards the heel for my liking, but the coast looks pretty spot on. What I'm going to do then is whack the .032" shim back in, hopefully this will bring the pattern in a bit on the drive side and also bring the backlash down a bit. Does that sound right to you guys?

Cheers again, Andy
 
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