Inconsistent backlash measurements

[cdygibson]

Hello I ordered dana gears for my jeep from East Coast Gear. Ended up receiving a Yukon front set. They gave me some money back I decided to keep them and install them. Anyway now I have about .011 variance in my back lash number. Is it the gears? My install? How do I check this?

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[Mudduck]

@chevymitchell may have a quick answer.

 

[LazyJL]

What does the pattern look like? Photos would be helpful.

 

[cdygibson]

I didn't run a pattern. I wasn't going to take it any further if the gears are no good. It goes from tight to over .011 it just seemed there was something else going on. That's with all the factory shims seemed it should be fairly close.

 

[dstevens]

I've re-geared but are not an expert. I'd say that it could be
- cap torque inconsistent
- insufficient carrier bearing pre-load
- ring gear not seated / inconsistent bolt torque
- incorrect pinion pre-load
- bad bearings (either pinion or carrier)
- over use of a case spreader
I'd see how much carrier pre-load there is and after that check for carrier run out.

 

[Nvdardx28]

I didn't run a pattern. I wasn't going to take it any further if the gears are no good. It goes from tight to over .011 it just seemed there was something else going on. That's with all the factory shims seemed it should be fairly close.

How are you going from tight to over .011", what size shim are you changing?

 

[cdygibson]

Well the carrier preload is what it was factory. I didn't change shims or carrier. Didn't use a case spreader. Carrier runout I guess could be an option

 

[cdygibson]

I didn't change the shims. That's just checking different points around the ring gear.

 

[Nvdardx28]

I didn't change the shims. That's just checking different points around the ring gear.

I see, so just a new ring gear of the same gear ratio? What happened to the old one?

 

[cdygibson]

New gear ratio went to 4.56. I just started with the factory shims as a base line.

 

[Nvdardx28]

Ohh ok I see what your measuring now. Did you put a new pinion race in? Are you confident it's seated completely?

 

[cdygibson]

Ohh ok I see what your measuring now. Did you put a new pinion race in? Are you confident it's seated completely?

I never took any races out I reused the bearings. It just hit 20k miles and everything looks brand new. Only bearing I pulled was on the pinion. I reused it and the factory pinion shim. Its a dana 30 the 44 I believe wouldn't be shimmed the same.

 

[roaniecowpony]

I come from decades of precision machining, being a machinist for a decade, then quality control and later a manufacturing engineer with a machining specialty. What I would do in your position, is remove the ring gear, and place your indicator on the differential face where the ring gear bolts, with the differential mounted in the housing and spin the diff and make sure that surface is running true. If so, you either have some problem with the ring gear seating against that surface or a bad ring gear. Alternatively, many ring gears hang over the differential flange and you can get an indicator on it. If you get a good runout there, and have a lot of backlash variance, but only one variation per ring gear revolution, it's a bad ring gear. If there are multiple, like 4 tight and loose variations in backlash per ring gear revolution, it's the pinion gear not running true.

 

[grimmjeeper]

It's easy to damage bearings when you pull them. I never reuse bearings when I do a new gear set, even when I use a quality bearing puller.

A bearing that is damaged or just not seated correctly can result in backlash problems like this. How did you remove the old bearings? How did you install them?

 

[cdygibson]

I come from decades of precision machining, being a machinist for a decade, then quality control and later a manufacturing engineer with a machining specialty. What I would do in your position, is remove the ring gear, and place your indicator on the differential face where the ring gear bolts, with the differential mounted in the housing and spin the diff and make sure that surface is running true. If so, you either have some problem with the ring gear seating against that surface or a bad ring gear. Alternatively, many ring gears hang over the differential flange and you can get an indicator on it. If you get a good runout there, and have a lot of backlash variance, but only one variation per ring gear revolution, it's a bad ring gear. If there are multiple, like 4 tight and loose variations in backlash per ring gear revolution, it's the pinion gear not running true.

I will look at this next.

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