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.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

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.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

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.