GM 12 Bolt Ring and Pinion Paint Reading Help

[SkippyDan]

Hello everyone, I am completly new to this and thought I had it down watching youtube but aparently not lol. I am trying to read the paint spread on my 12 bolt axle and am having trouble trying to figure out what I need to do. I am reusing the old pinion and ring but have all new bearings installed. I am using new shims on one side since the one was pretty beat up but still have one of the old ones with a small shim on the other side. I made sure to keep it the same size as the old ones and it equals out but ive been adjusting slightly everytime and it just doesnt seem right. There was only one shim on the pinion but it got taken off because I thought it was making the backlash too tight. as it sits in these pictures Im reading .008 and that seems all good but i cannot seem to get it to line up like it should. Im making sure to put a load on it when im spinning it but ive seen some diagrams of "if it looks like this do this" and Im just lost. Any help would be greatly appriciated. Thank you.

 

[ali_c20]

When replacing bearings the old shims are just a starting point. It's always setting up anything from scratch.
I would replace all shims with new ones and start from scratch.

Focus on the drive side, if you have a real good drive side pattern your coast pattern should be fine too.

It's a lot of work when you not often do ring and pinion setups. It took me and a friend ~5 hours to get it right on my K5.

This video it has some good info.

https://www.youtube.com/watch?v=0Lzw1wPgc8U

 

[legopnuematic]

When setting up used gear sets, you only should be looking at the coast side of the ring gear. Used gears will almost never give a good pattern to read on the drive side.

Pinion depth is first, then backlash. Don’t make changes to the pinion height to change backlash!

What I do if I’m just doing bearings and ring and pinion and housing are the same, is take the new inner pinion bearing and race and measure it’s effective height compared to the old bearing and race:

Old bearing and race

New bearing and race. .002 difference. I adjusted my shim to compensate.

You must be registered for see images attach

Truthfully, a .002 difference in pinion depth on used gears is unlikely to cause any issues though.

Anyways, get the pinion depth corrected, start with the original shim (or use new shims equaling the OE shim). Then with the carrier biased away from the ring gear, check the backlash, make adjustments as needed to the carrier shims to bring backlash into spec. Ideally you would have measured backlash before the teardown, if you didn’t shoot for the .006-.008 range on backlash.

 

[Turbo4whl]

When setting up used gear sets, you only should be looking at the coast side of the ring gear. Used gears will almost never give a good pattern to read on the drive side.

This is not correct. ^^^

You are correct about the new bearings, cups and cones. They don't vary much.

Truthfully, a .002 difference in pinion depth on used gears is unlikely to cause any issues though.

Anyways, get the pinion depth corrected, start with the original shim (or use new shims equaling the OE shim). Then with the carrier biased away from the ring gear, check the backlash, make adjustments as needed to the carrier shims to bring backlash into spec. Ideally you would have measured backlash before the teardown, if you didn’t shoot for the .006-.008 range on backlash.

This is good. ^^^

The coast side of the ring gear is not moving the truck, the drive side is. There is a good way to read the drive side pattern. Since the load is on the drive side, you need to add resistance to the gearset. Couple ways to do this. After you add your marking compound, use a pry bar to hold resistance on the ring gear, turn the pinion though the ring gear. Since the load you add is much less than the load of moving the truck, you want the pattern low on the tooth, not high running off the top.

Another way, (may require two people) wrap rags around the oil slinger and hold resistance there. Use a wrench on a gear mounting bolt, drag the ring gear past the pinion.

 

[CalSgt]

you need to add resistance to the gearset.

^^^^ This

My preferred way is to lightly drive a chisel between the housing and the ring gear or edge of the carrier and turn the assembly using the pinion nut. It takes a few times to figure out exactly where to put the chisel and how far to tap it in. You will need to put the chisel at the bottom and top of the ring gear depending on which way you are turning, the gear will pull the chisel tighter while spinning one way and spit it out going the other. I've also used a hammer handle as a prybar between the housing and carrier/ring gear while having someone else turn the pinion nut, this doesn't seem to add as much tension as the chisel method.

Another thing I have discovered helps is thinning the pattern dye a little, I mix a few drops of oil or transmission fluid into the paste before painting the teeth.

It's a lot of work when you not often do ring and pinion setups. It took me and a friend ~5 hours to get it right on my K5.

This video it has some good info.

https://www.youtube.com/watch?v=0Lzw1wPgc8U

@ali_c20 is right, you need to approach a gear set-up by planning on it taking all day or two. Never install the carrier thinking its the final time because it will just lead to disappointment.

 

[idahovette]

THAT'S when you need the Bullet!!!!! Right Casey?

 

[legopnuematic]

This is not correct. ^^^

For used gear sets it is.

You must be registered for see images attach

The coast side of the ring gear is not moving the truck, the drive side is.

Which is why the coast side is the primary consideration for used gears.

The goal of setting up used gears is to match/reproduce the original setup, because the wear is primarily focused on the drive side the likelihood of the pattern reading the same as it was when setup is lower, whereas the coast will lack that wear, allowing it to produce a pattern closer to that of its original setup.

That is how I work with used gear sets, my intention is to maintain the mated/developed pattern of the previous setup, not to compensate or improve it. Same goes for backlash, I measure before disassembly and aim for that original number on reassembly.

None of this really matters for OP, as they state it’s the same ring and pinion, just installing new bearings.

 

[CalSgt]

THAT'S when you need the Bullet!!!!! Right Casey?

LOL YUP!

After pulling a carrier assembly and pinion out of a rear end 7 times to make adjustments and finally coming up with acceptable pattern, backlash, pinion TTR and total TTR (bearing preload) it would definitely be time for a bullet.

We refer to those as a "Victory beer"...