Ring to pinion backlash question

[JasonS]

I purchased a deuce differential assembly with the intent of installing an ARB air locker, then swapping that with the one currently in the rear of my bobbed deuce.

The ring to pinion backlash is ~0.020" versus the spec of 0.005" to 0.015". While there are shims that can be removed to move the ring closer to the pinion, my question is whether this amount of wear is acceptable/ normnal and if I should simply adjust the depth with the shims or look for something in better condition. There is nothing otherwise or obviously wrong with the ring/ pinion to my untrained eye. The bull gear backlash is in spec.

Thoughts or suggestions?

 

[rustystud]

When I was rebuilding differentials on a daily basis, I never went past .016" for backlash. Even on the most worn gears. Anything past .016" just brings problems down the road with the gears "slamming" into each other when shifting manual transmissions or going back and forth between reverse and forward gears. This accelerates bearing and gear wear. Plus, the possibility of losing teeth is much higher. There is also the wear on the axles and side gears due to this "slamming" effect.
So, if you can adjust the backlash down to .010" to .012" that would be so much better.
I would then check your tooth contact pattern. Try and keep it in the center as much as possible.

 

[Mullaney]

I purchased a deuce differential assembly with the intent of installing an ARB air locker, then swapping that with the one currently in the rear of my bobbed deuce.

The ring to pinion backlash is ~0.020" versus the spec of 0.005" to 0.015". While there are shims that can be removed to move the ring closer to the pinion, my question is whether this amount of wear is acceptable/ normnal and if I should simply adjust the depth with the shims or look for something in better condition. There is nothing otherwise or obviously wrong with the ring/ pinion to my untrained eye. The bull gear backlash is in spec.

Thoughts or suggestions?

.
Hi Jason,

It might help a little to have a visual... Blue Machinist Dye will give you a picture.

I found a nice article that explains what you want to see.
Also created a PDF of the page below if it disappears at some time in the future.

How To Create & Read Ring Gear Patterns

Gear tooth patterns are harbingers… they can foretell whether your ring and pinion gear set is going to live a long and prosperous life or if it’s doomed to an impending catastrophic failure. Pulling off a proper differential setup comes down to precise adjustments.

www.yukongear.com

 

[JasonS]

Rusty and Mullaney, thanks for the insight. I agree that the differential should not be run as is. What I am wondering is will it likely be OK once the backlash is set properly or should I try to get a differential that is in better condition?

 

[rustystud]

Rusty and Mullaney, thanks for the insight. I agree that the differential should not be run as is. What I am wondering is will it likely be OK once the backlash is set properly or should I try to get a differential that is in better condition?

If your gears look OK and the bearings are OK, run it.

 

[87cr250r]

There are two sets of numbers. The specification and the service limit. The 0.005-0.015 would be specification and is what you set the clearance to be when assembling. The service limit is the clearance when the assembly is considered worn out and should be removed from service. I don't know what your service limit is. However, there isn't much wearing that goes on in either the tapered roller bearings or on the gear teeth so large backlash measurements mean it was either set up incorrectly or is failing.

 

[rustystud]

There are two sets of numbers. The specification and the service limit. The 0.005-0.015 would be specification and is what you set the clearance to be when assembling. The service limit is the clearance when the assembly is considered worn out and should be removed from service. I don't know what your service limit is. However, there isn't much wearing that goes on in either the tapered roller bearings or on the gear teeth so large backlash measurements mean it was either set up incorrectly or is failing.

Actually I've seen backlash measurements of .016" to .020" on older gear sets that only needed the bearings tightened up a bit and the backlash reset. You will get small amounts of wear on larger bearings like .001" to .002" due to normal wear. So figure your gearset has run 100,000 miles. Thats not the end of service life on large differentials, which can go to 500,000 miles and then some. Especially if you have taken care of them and changed out the gear oil on a regular basis like the manuals say. Add this amount of wear, to the wear the gear-set itself will have normally like a couple of thousandths and "Wa-la" ! you have backlash of .018" to .020" .
So on these units you would just give them a "freshening up" like tightening up the bearings preload and reset the backlash. Now is this gearset going to last another 500,000 miles ? Of course not, but it will last another 80,000 to 100,000 miles easily.

 

[87cr250r]

It is recommended when servicing worn gear sets to measure backlash prior to disassembly and reset to the previous backlash number, not the specified number.

 

[rustystud]

It is recommended when servicing worn gear sets to measure backlash prior to disassembly and reset to the previous backlash number, not the specified number.

Recommended by who ? In all the rebuild shops I worked in, gearsets are set by the gear pattern. Not some arbitrary number. You use the backlash as a "guide" , not the "be-all end-all" .
Thats the difference between "book" learning and "real life experiance" .

 

[87cr250r]

Recommend by Dana Spicer. This is very important because of you try to set a worn gear sets to new backlash values the tip of the tooth can bottom out in the root of other gear.

 

[JasonS]

All, I appreciate your suggestions. However, none of what has been posted makes me feel any better about keeping this differential. I bought what was advertised as in "good" condition from a truck with low miles and this one is not.

 

[87cr250r]

My suggestion would that unless you see signs of a bearing failure or the pinion nut has backed of is to run it as is. The wear pattern on the gears still looks normal, no?

 

[rustystud]

Recommend by Dana Spicer. This is very important because of you try to set a worn gear sets to new backlash values the tip of the tooth can bottom out in the root of other gear.

View attachment 885422

View attachment 885426

If you had worked in the industry you would know that the factory says this to prevent the gear set from "singing" (making noise). Most customers of light vehicles do not like noise coming from their differential. Now big trucks owners like longevity over noise. Setting the gearset to a corrected pattern will allow the gearset to last longer something the "factory" is not interested in. They want to sell you a new gearset. Any mechanic who has been in the differential rebuild business knows this.
Don't worry, I'm not going to trot out all my years of experience and say you don't know what you're talking about so shut up.
You have a valid point. It's just that the gearset can last longer if rebuilt correctly.

 

[rustystud]

All, I appreciate your suggestions. However, none of what has been posted makes me feel any better about keeping this differential. I bought what was advertised as in "good" condition from a truck with low miles and this one is not.

Take it back then. Tell them your concerns and show them what you're talking about.
If you don't trust your differential, you will not have good travelling experiences as you will be worrying about the differential blowing up. That kind of nagging feeling can ruin any road trip.

 

[JasonS]

I have attached two pics of the gears for review.

 

[rustystud]

I have attached two pics of the gears for review.

You do have some wear I see on the "Ring gear" though the "pattern" on the pinion is a good one.
How are the bearings ? You should be able, by using a flashlight to look at the bearing races and see if there is any grooves or other wear patterns on them. If there is then don't use it.