Pinion depth way off

[Ryanbrown36]

I’m doing a rebuild on a g80 10 bolt that I got for cheap, throwing in 3.73 gears and this is my first time doing it. I’m at the point now where I’m setting my pinion depth and the number it calls for is 4.257, the closest I can get is 4.555 and that’s with way too many shims. Good chance this is something stupid on my end but I don’t know what else to check. Old one came out with a .036” shim and if I re use that one with the new pinion I’m getting 4.620. All the new races are in, and the old bearings came off well enough to make them setup bearings (my local speed shop confirmed this) any ideas of what else to check would be greatly appreciated.

 

[legopnuematic]

How are you checking pinion depth/arriving at those measurements?

Not saying pinion depth tools don't work, but really the best way is start with the OE shim thickness, get back lash in spec, run pattern with marking compound, make the determination if it's deep or shallow, make a .005 shim adjustment, repattern and see how it looks, if it was first deep, then shallow, the ideal shim is in-between those two, or vice versa.

 

[Ryanbrown36]

How are you checking pinion depth/arriving at those measurements?

Not saying pinion depth tools don't work, but really the best way is start with the OE shim thickness, get back lash in spec, run pattern with marking compound, make the determination if it's deep or shallow, make a .005 shim adjustment, repattern and see how it looks, if it was first deep, then shallow, the ideal shim is in-between those two, or vice versa.

I was using a 1/4 plate accross the house and using verniers to measure then subtracting the 1/4” from the measurement. This was just the way I was told to do it and then do the whole marking compound method.

 

[77Dmax]

You have to verify that the bearing cap is actually dead nuts half the race diameter. Not terribly uncommon for it not to be. Also make sure your 1/4 plate is .250.

A dial caliper is far from ideal for this measurement. A depth mic is what you need.

I would also start with the factory shim and see the pattern. I've set up dozens like this with success. Read the pattern and it'll tell where to go.

When taking the measurements i always tighten the pinion nut to the desired bearing preload is met. Crush collar out of course..

 

[Ryanbrown36]

You have to verify that the bearing cap is actually dead nuts half the race diameter. Not terribly uncommon for it not to be. Also make sure your 1/4 plate is .250.

A dial caliper is far from ideal for this measurement. A depth mic is what you need.

I would also start with the factory shim and see the pattern. I've set up dozens like this with success. Read the pattern and it'll tell where to go.

When taking the measurements i always tighten the pinion nut to the desired bearing preload is met. Crush collar out of course..

dumb question but could further explain what you mean by the bearing cap being half the race diameter, I didn’t see that in the videos I watched so I’ve got no clue what you mean by that. I did verify the plate was actually .250 and will do it the marking compound way after school tomorrow.

 

[77Dmax]

to make it easy to explain lets say the race has an OD of 5". Half of that is 2.500". The natural assumption is the bearing cap and the housing are both 2.500" making the parting line dead nuts in the middle. Well the bearing cap could be 2.450" deep and the housing side 2.550". You would need to take .050 off your depth measurements to be at the actual centerline.

You need to verify these measurements and adjust your numbers accordingly.

Measure the OD of the carrier race and divide by two. Then measure the depth of the bearing cap. See where it lands..

Unfortunately you'll need something more precise than a dial caliper, but it should get you moving in the right direction..

 

[legopnuematic]

I did make a pinion depth tool, like the TD one available. I am a machinist by trade so I was able to whip it up after work.

I tried it once, then went to just going by the pattern. The pattern is going to be the final say in the whole deal anyways.

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Also nothing wrong with using setup bearings, but I would recommend checking the height of the new bearing and the setup bearing with the same race on both, bearings are tight tolerance on their ID and ODs but the overall length can vary .005-.010, even same brand/part number bearings. For some applications like a front hub or full floating rear hub that doesn't matter at all. But a .005 difference on a an inner pinion bearing will throw a good setup off.

 

[Ryanbrown36]

to make it easy to explain lets say the race has an OD of 5". Half of that is 2.500". The natural assumption is the bearing cap and the housing are both 2.500" making the parting line dead nuts in the middle. Well the bearing cap could be 2.450" deep and the housing side 2.550". You would need to take .050 off your depth measurements to be at the actual centerline.

You need to verify these measurements and adjust your numbers accordingly.

Measure the OD of the carrier race and divide by two. Then measure the depth of the bearing cap. See where it lands..

Unfortunately you'll need something more precise than a dial caliper, but it should get you moving in the right direction..

Okay thanks for clarifying, I will check the pattern tomorrow as I don’t have many measuring tools other than the borrowed verniers I have now. But I will still measure that stuff for piece of mind and to learn how to do it all.

 

[Ryanbrown36]

I did make a pinion depth tool, like the TD one available. I am a machinist by trade so I was able to whip it up after work.

I tried it once, then went to just going by the pattern. The pattern is going to be the final say in the whole deal anyways.

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Also nothing wrong with using setup bearings, but I would recommend checking the height of the new bearing and the setup bearing with the same race on both, bearings are tight tolerance on their ID and ODs but the overall length can vary .005-.010, even same brand/part number bearings. For some applications like a front hub or full floating rear hub that doesn't matter at all. But a .005 difference on a an inner pinion bearing will throw a good setup off.

I have measured everything possible I could measure to ensure everything going on and that I’m using for setup is the same, as I’m learning as I’m going here so really want to make sure it’s all right. Do you think a good next step would be to throw the carrier back in and see the pattern before any more measuring. Would like to keep it as simple as possible while still doing it right.

 

[TotalyHucked]

I just went through this with the 8.6 10-bolt in my daily '05 Silverado. Spencer was a huge help as well as a couple other guys. After doing alot of research about pinion depth measurements, it seems like 75% or more of guys that do it for a living say the pinion depth tools hardly ever get used. They use the original pinion shim with setup bearings, measure backlash and run a pattern with the gear paint. That seems to be THE way.

Through literally 2 months of trial and error, I can give a few tips. Do not cheap out on the gearset, my whole problem the first month and a half was a badly machined gearset. Like Spencer said, mic out your setup bearings and your final bearings to see what, if any difference there is. The Koyos I used all mic'd out to within .01 of each other thankfully. If they don't, you'll have to compensate for the height difference when you do the final setup. Then start with the factory pinion shim and then do big swings to see a difference and start to hone in there.

Pick up this book, I learned alot there:

Amazon.com

Here's my gear struggles, starting on page 8, if you want a long read lol:

Huck's daily - 2005 Z71 crewcab

I don’t understand the tinted windshield thing. I can barely see at night as is lol. But to each their own.

www.gmsquarebody.com

 

[legopnuematic]

First, the gears you are installing, are they new or is it a used gear set?

This is an 8.5 ten bolt correct? The OE shim depth should be .037” so the .036 shim you removed is more or less the ‘OE spec’

Start with that shim depth, I like to write down my pinion shim, and carrier shims, what the backlash was, and if the pattern was deep/shallow/acceptable. That way I can go back to a previous combination and know where I’m at if I get pulled away for some time. Good to take pictures and label them to provide some reference to compare.

Here is an example of that from a 14 bolt semi float I did. Note, the 14b sf uses a single side adjuster and shims on the other side for carrier adjustment/preload, so that’s why there is only one set of numbers for carrier shims. For a 10/12/Dana you’d have shims on both sides.

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If you are not using a housing spreader, get the carrier to zero play or lightly preloaded, keep an idea of your total carrier shims, then if you add .005 to the drivers side, remove .005, or vice versa. Then when you arrive at your final setup, add .005 shim to each side to preload the carrier bearing. The carrier should have to be tapped into place (if not using a spreader).

 

[legopnuematic]

Oh, and I can’t stress enough, cleanliness in all aspects is key, clean housing, clean gears, clean shims, clean bearings (don’t spin dry bearings though!), clean caps, clean bolts, everything clean and burr free.

Burrs and dirt are no bueno!