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So my dad and I are new to setting up a ring and pinion and we have some questions about getting it setup so it will last as long as possible. Were currently just mocking it up right now with all the used stuff to see if we can figure out how to setup backlash but we need some help. The pattern looks good but there is no backlash at all right now(the old 2.72 gears only had .001 backlash before we removed them). What do I need to adjust to get to .006 backlash per Motive Gear specs? Do I adjust the pinion depth or do I need to move some carrier shims around? We have the factory really thick shim on the drivers side and several thinner shims on the passenger side of the carrier. Also, how do you set pinion nut torque with new bearings, races and crush sleeve? Should I leave the carrier in or take it out? My new gears are 3.73s if that makes a difference
I would start with moving the ring gear away from the pinion to increase the backlash and then recheck the pattern. You may then have to reset the pinion with a thicker shim, then check the backlash again. Its an iterative and sometimes frustrating process. One adjustment affects the other, but you will eventually get there. I had an extra inner pinion bearing machined a few thousandths larger ID so it would slide on and off of the pinion bearing without pressing. Once the setup was correct, I pressed on an unaltered bearing for the final assembly.
When you are doing the initial setup, leave out the crush sleeve on the pinion and just tighten the pinion nut until the pinion bearings have no play and a little bit of drag. For the carrier bearings, same thing for initial setup, no preload, just tight enough to remove the play.
Once you have the gear pattern and backlash right, then install the crush sleeve and tighten the pinion nut until you get to the specified rotational drag on the pinion bearings, measured with a dial type inch pound torque wrench. Then you install the carrier with shims and measure the new rotational drag on the pinion. It should be more than the pinion alone and this difference x 3.73 is the preload drag of the carrier bearings (you have to account for the mechanical advantage of the gear set for this measurement). Add equal shims on both sides of the carrier to bring the bearing preload drag up to specification.
We now have .007 backlash and this is the new pattern with both factory shims. The ring gear is stamped with .006 but its so close were afraid to mess with it anymore. My next question is "how do you get the inner pinion race out?". We need to change the pinion bearings since we made the old inner bearing slip-fit
Last edited by Red86SS; 08-06-2019 at 05:42 PM.
Reason: Added more information
0.006” backlash should be OK. The pattern looks pretty good in the wide dimension of the gear tooth, but just a little bit shallow in the short dimension (looks like it is running off of the edge of the tooth). Did you use the same size pinion shim that was on it before? I would try a pinion shim a few thousands thicker than the one you have now. It will probably tighten the backlash a little, so you may need to shim the carrier over to compensate. The pattern is really close and would probably be ok, but I would try to get it a little bit better if you can.
For the pinion race, do you mean the outer race that is pressed into the axle housing? There should be clearance slots in the housing so you can get in there with a large punch and hammer to pound it out. A bearing race driver kit and hammer works well to install the new ones.
Yes we have the same super thin shim on the pinion that it had before and yes I mean the outer race pressed into the housing, i was just wondering if there were slots on the backside to knock it out with. Thank you for your help! My dad and I both very much appreciate it!
You’re very welcome. Definitely get the new outer races installed before doing any more gear setup. A worn race could affect the pinion depth a bit.
This is where a setup bearing (new inner pinion bearing with the inner race machined for about 0.001” clearance) will help. You can easily change pinion shims without having to press the bearing on and off every time. Once you get the final setup right, press on a new unaltered bearing. It will be dimensionally close enough.
These are the gear pattern setup photos from when I did mine. Glenn from 9-Bolt.com walked me through the setup. This is a 9-bolt with new Motive 3.70 gears, but yours should set up very similar. Your pattern is very close to this, but you want to see a little bit of a yellow line at the top edge on both the drive and coast sides of the gear.
Oddly enough, the first thing we did was machine the inside of the old inner bearing so we could change shims easily. I went back out and turned the diff 10 times in each direction instead of 3 and this is my pattern now
Try going a bit heavier on the marking compound. It should make the pattern stand out a little better. You want to see just a little bit of yellow on the top edge. Right now, it looks like it is running off of the edge, but it could just be that there isn't enough compound on there to show it clear enough.
Also, make sure to use a new unaltered pinion bearing that has the proper interference fit when you do the final setup. If you don't have access to a hydraulic press, an easy way to install it is to put the pinion gear in the freezer overnight and then put the bearing in the oven at 400 degrees for about 15 minutes. Take the pinion gear out of the freezer, stand it up on the table gear end down, drop the shim on then grab the bearing from the oven with an oven mitt and drop in on the pinion shaft. It will slide right on, then let the temperatures equalize before you move it.
We've already got the inner pinion bearing pressed on since we have a 20 ton press and both new pinion races are seated as well. I was told to go easy on marking compound since we havent had any luck finding any locally
The pinion is in for good now! The FSM said pinion nut torque should be 24-32 inch lbs and we got it to 30 all the way around. However, we didn't put any threadlocker on the pinion nut since we havent done this before but i'm looking into some blue medium strength wicking loctite #220 because we dont want to take the nut off and ruin the preload we have. I have the final backlash pictures but haven't got the numbers yet. My dad put a bunch of compound on the gears this time, rotated it each direction 6 times while pressing on the carrier a bit and its more than halfway down in the valley between the gears on the drive side so its got plenty of contact now. The coast side looks good too but it'll be on the drive side majority of the time
Last edited by Red86SS; 08-11-2019 at 11:10 AM.
Reason: Forgot to add something
You’re very welcome. Definitely get the new outer races installed before doing any more gear setup. A worn race could affect the pinion depth a bit.
This is where a setup bearing (new inner pinion bearing with the inner race machined for about 0.001” clearance) will help. You can easily change pinion shims without having to press the bearing on and off every time. Once you get the final setup right, press on a new unaltered bearing. It will be dimensionally close enough.
I love the idea of a new but altered bearing. We sure appreciate all the help and guidance thru this. Just tryin my best to get it right and not have it howl or wear out fast. Feel pretty good about the contact myself except the slight fanning on the coast side.
Just checked the backlash. It is .007"
The pattern looks better this time with more marking compound. One thing you said in an earlier post is that you have 30in-lb of pinion nut torque. I think you mean pinion rotational drag. The pinion nut torque will be much higher than that to compress the crush sleeve. Just wanted to clarify what you said.
Have you measured the rotational drag of the carrier bearings yet? That would be the next step.
I don’t know the carrier bearing preload spec on the 10-bolt off the top of my head, but your measurement sounds like it might be high. I would suggest looking it up in the service manual. 43-30=13x3.73=48.5in-lb. I think the spec is closer to 25-30. May need to change out the carrier shims. If you do, just take out the same amount of thickness from each side and it won’t change the gear setup.
It has the same shims and carrier bearing preload that it had before we started working on it, we havent changed anything but the ring gear itself and the pinion. It should have the same exact carrier bearing preload that it had from the factory. I appreciate your input on it and all the help you've given us!
Last edited by Red86SS; 08-12-2019 at 10:35 PM.
Reason: Not enough info
Then yes, your carrier bearing preload is whatever it was before you took it apart.
I just want to report in and say that 4 years later, this differential is working great and the help setting it up was so greatly appreciated!
I always like to report back how things went!
This car now has a Holley Sniper EFI system and is powered by a stout 400 SBC, built in house. It was running 13.4's before my son changed out my old school Holley carb and HEI for the new Holley Sniper setup.
TYVM @TransamGTA350
08-05-2019, 07:31 PM
