Gear Pattern Check

hosejockey61 said:
Yeah, Yukon is weird like that. Factory new bearing specs are different from year to year even though it's the same axle, not sure why. It's minimal so probably not a big deal. I never tighten bearings to the high side of factory spec. If I'm shooting for 16-20 and end up at 22, I'll still run it. If it's at 35 I'll reset.
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Going over a little isn’t going to hurt it. I usually try to set up in the middle to upper end because the bearing do wear into the races a little.
If you’re ever really bored…. Do a gear setup and do a break-in. Then drive it another 250 miles. Tear it down and recheck your preload, you’ll be amazed.
The gears that I despise setting up are Richmond, I can never get a uniform BL reading.
 
williambmac said:
Going over a little isn’t going to hurt it. I usually try to set up in the middle to upper end because the bearing do wear into the races a little.
If you’re ever really bored…. Do a gear setup and do a break-in. Then drive it another 250 miles. Tear it down and recheck your preload, you’ll be amazed.
The gears that I despise setting up are Richmond, I can never get a uniform BL reading.
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BTDT. That is the whole purpose of pre-load. They will break in and settle where they do. By torqueing to the higher spec you risk burning up your bearings. The specs are there to get it set up correctly so it will wear correctly and settle in.

If you were to take your same scenario, and after the break in tighten the preload back up, you will most likely damage the gear set.
 
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hosejockey61 said:
BTDT. That is the whole purpose of pre-load. They will break in and settle where they do. By torqueing to the higher spec you risk burning up your bearings. The specs are there to get is set up correctly so it will wear correctly and settle in.

If you were to take your same scenario, and after the break in tighten the preload back up, you will most likely damage the gear set.
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Totally agree. Years ago at the GM training facility, They had us assemble a diff in a Tahoe. You had to demonstrate the correct usage of the GM required tools, and we had to show correct preload, backlash and pinion depth measurements.
The class instructor drove the vehicle home that night. The next day we had to tear it down and recheck the preload and backlash.
It loosened up quite a bit from a 160 mile trip.
 
williambmac said:
Factory spec is .005-.008. Yes, it does differ depending on the manufacturer, most aftermarkets are .006-.010. Yukon spec is .010-.015 which I think is obscene.
Factory spec for pinion preload is 15-30 in lbs, but aftermarket gear manufacturers give a spec of 12-15.

I always set up to factory spec and have never had a failure.
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I think a lot of folks obsess a bit over this aspect of gear setup. With the exception of two cut gears which require tight backlash as they actually wear in their own pattern I just try to make sure backlash is above .006. If you have a good pattern and you are at .010 there would be no harm running it that way. I have also had gears that just made an ugly pattern if I tried to go less than .010.

I also think Yukon calls out their high spec because they are worried the DIYer might not measure accurately and do not want to risk burning the gears because of it.
 
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Blackjack said:
I think a lot of folks obsess a bit over this aspect of gear setup. With the exception of two cut gears which require tight backlash as they actually wear in their own pattern I just try to make sure backlash is above .006. If you have a good pattern and you are at .010 there would be no harm running it that way. I have also had gears that just made an ugly pattern if I tried to go less than .010.

I also think Yukon calls out their high spec because they are worried the DIYer might not measure accurately and do not want to risk burning the gears because of it.
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That just gave me a flashback to my 2-cut gear challenge…..
 
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Not to sidetrack this thread or jinx myself.
Here is a pic of the a gear install I did a few years ago. It didn’t fail due to a setup issue. It failed because the customers 2016 camaro was putting out close to 900 hp without the 250hp shot of nitrous.
8AA5F625-B1F4-4276-85C2-B7F332A7CFF4.jpeg
 
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williambmac said:
Not to sidetrack this thread or jinx myself.
Here is a pic of the a gear install I did a few years ago. It didn’t fail due to a setup issue. It failed because the customers 2016 camaro was putting out close to 900 hp without the 250hp shot of nitrous.
View attachment 314262
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I worked at GM dealerships for 20+ years before opening my own hot rod and restoration shop. At the dealership, the customer would be trying to get this fixed as a come-back, talking about my sloppy work. At my hot rod shop, the same guy would be going "Look what I did!" with a big grin on his face.
 
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Old_Crow said:
I worked at GM dealerships for 20+ years before opening my own hot rod and restoration shop. At the dealership, the customer would be trying to get this fixed as a come-back, talking about my sloppy work. At my hot rod shop, the same guy would be going "Look what I did!" with a big grin on his face.
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The customer has been a long time customer of mine. He was showing off in front in front of the dealership.
When he blew it up, he tossed me the keys and said “I think I blew the rear end, can you fix it for me.”
I ended up putting a whole new stock assembly in it.
He immediately traded it in for a 2017 Corvette Grand Sport.
He drove the GS for a couple months, then traded it in for a Z06, because the GS wasn’t fast enough.
The sad thing is…. Ron buys a car, puts a ton of money into mods, then trades it in because it’s not fast enough.
 
williambmac said:
Not to sidetrack this thread or jinx myself.
Here is a pic of the a gear install I did a few years ago. It didn’t fail due to a setup issue. It failed because the customers 2016 camaro was putting out close to 900 hp without the 250hp shot of nitrous.
View attachment 314262
Click to expand...
This pic makes me want to mill an o-ring channel into my 14-bolt. That looks really, really convenient.
 
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Old_Crow said:
I worked at GM dealerships for 20+ years before opening my own hot rod and restoration shop. At the dealership, the customer would be trying to get this fixed as a come-back, talking about my sloppy work.
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Working for a GM dealership, I can tell you customers still try that.
We get Uber drivers asking us to warranty an engine that has 180k miles.
 
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Mike_H said:
Is that here or Jeep forum?
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This is the thread. I was setting up the gearset in my previous high pinion pro-roc 60, and the pattern was driving me nuts.

https://wranglertjforum.com/threads/ring-and-pinion-gear-pattern-help.44201/
Fortunately, there is quite the gearset braintrust here.

Turned out I had a 2-cut, face hobbed gearset, which produces a markedly different pattern that a 5-cut, face milled, gearset.

If you are interested, here is a description.

https://www.differentials.com/two-cut-vs-five-cut-gears/
 
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williambmac said:
The customer has been a long time customer of mine. He was showing off in front in front of the dealership.
When he blew it up, he tossed me the keys and said “I think I blew the rear end, can you fix it for me.”
I ended up putting a whole new stock assembly in it.
He immediately traded it in for a 2017 Corvette Grand Sport.
He drove the GS for a couple months, then traded it in for a Z06, because the GS wasn’t fast enough.
The sad thing is…. Ron buys a car, puts a ton of money into mods, then trades it in because it’s not fast enough.
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I had a guy with a '57 Chevy like that. In 6 years I pulled 3 perfectly good engines out of that car and replaced them with bigger ones...just because. I also pulled an axle shaft out of the rear end that had a crack running the entire length of the axle and completing a full revolution of the axle in that distance. Before that I pulled another axle that he had totally sheered where it went into the splines on the side gear. Dude actually built an 1/8 mile strip on his property so he could run his car.
 
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Old_Crow said:
I had a guy with a '57 Chevy like that. In 6 years I pulled 3 perfectly good engines out of that car and replaced them with bigger ones...just because.
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I love buying the cast-offs from folks like that. Pennies on the dollar!

I don't miss the dealer at all, stupid comebacks because the customer is ignorant or an outright liar.
 
Ok... really happy with this for my Dana 30... 24 thou on the pinion, 15 left and 30 right. BL exactly at 6.

Took me a few tries...but I finally sorted through all the information and figured out and if, then chart. I appreciate all the good advice and assistance!

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