Ford 8.8 ring gear contact patch always favors heel edge

[ylidk]

Hey all, I am regearing my truck from 3.08's to 3.55's and replacing the open diff to a limited slip. All used, stock Ford parts. I am having trouble getting the contact patch looking good though, the drive side always seems to favor the toe edge while the coast side always seems to favor the heel edge. Based on the Ford guide (image below) this implies that the pinion shim needs to be thinner, but I dropped from 0.032 all the way down to 0.010 in steps, and the coast side was always on the heel edge. I was able to get the drive side looking okay at 0.027" pinion shim thickness, and with backlash at 0.008" shown in the image below. I can live keeping that drive side pattern at 0.027" pinion shim thickness, but the coast side looks pretty bad, and nothing I change seems to do much at all? At 0.010" It actually seemed more dramatically at the heel edge than higher shim thicknesses. Any ideas? Been at it for a few days and it's about to rain for a week straight here, so I want to have this project sealed up before then if I can. TIA!

 

[2011Supercab]

Backlash is adjusted by moving the carrier to one side or the other by changing the shims on the sides of the carrier.

Not by changing the shims on the pinion gear

 

[ylidk]

Backlash is adjusted by moving the carrier to one side or the other by changing the shims on the sides of the carrier.

Not by changing the shims on the pinion gear

Backlash spec is 0.008" to 0.012", and my backlash is measuring in at 0.008". My pattern has always kept looking similar to example B. in ford's guide.

 

[2011Supercab]

every time you change pinion depth you need to recheck the backlash

 

[ylidk]

every time you change pinion depth you need to recheck the backlash

Yep, I have been. I've had the gears out probably 50 times to get these shims changed around to make everything play nice but the pattern never looks good. Current backlash is 0.0085". About the best I can get it in the images above. How bad would it be to send it as-is? Does the contact pattern make you think the backlash is off or something?

 

[02FX4]

Hey all, I am regearing my truck from 3.08's to 3.55's and replacing the open diff to a limited slip. All used, stock Ford parts. I am having trouble getting the contact patch looking good though, the drive side always seems to favor the toe edge while the coast side always seems to favor the heel edge. Based on the Ford guide (image below) this implies that the pinion shim needs to be thinner, but I dropped from 0.032 all the way down to 0.010 in steps, and the coast side was always on the heel edge. I was able to get the drive side looking okay at 0.027" pinion shim thickness, and with backlash at 0.008" shown in the image below. I can live keeping that drive side pattern at 0.027" pinion shim thickness, but the coast side looks pretty bad, and nothing I change seems to do much at all? At 0.010" It actually seemed more dramatically at the heel edge than higher shim thicknesses. Any ideas? Been at it for a few days and it's about to rain for a week straight here, so I want to have this project sealed up before then if I can. TIA!




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Sometimes your pinion depth can cause excessive (coast) heel and (drive) toe patterns that can't be remedied by setting backlash. Most of the time you'll have to move the pinion in by removing a shim (or replacing with a thinner) and the try resetting your backlash.

 

[ylidk]

Sometimes your pinion depth can cause excessive (coast) heel and (drive) toe patterns that can't be remedied by setting backlash. Most of the time you'll have to move the pinion in by removing a shim (or replacing with a thinner) and the try resetting your backlash.

Yeah, I started with a pinion shim thickness of 0.032" and based on the ford guide the toe-heel pattern I was getting implied I needed to reduce shim thickness. I reduced in steps down to 0.010" shim thickness and made sure my backlash was within the 0.008"-0.012" range in the spec. At 0.027" pinion shim thickness the drive side had the most coverage, but the coast side was always leaning toward the heel during that entire range. By 0.010" the drive side was excessively toward the heel as well.

 

[02FX4]

Sometimes your pinion depth can cause excessive heel patterns that can't be remedied by setting backlash. Most of the time you'll have to move the pinion in by removing a shim (or replacing with a thinner) and the try resetting your backlash.

Yeah, I started with a pinion shim thickness of 0.032" and based on the ford guide the toe-heel pattern I was getting implied I needed to reduce shim thickness. I reduced in steps down to 0.010" shim thickness and made sure my backlash was within the 0.008"-0.012" range in the spec. At 0.027" pinion shim thickness the drive side had the most coverage, but the coast side was always leaning toward the heel during that entire range. By 0.010" the drive side was excessively toward the heel as well.

The coast side isn't all that critical, if you can get the drive side centered and even, then I'd send it as long as your backlash is within tolerance.

 

[ylidk]

Awesome, in that case I will set set get a few patterns tested around the 0.027" shim depth and send it. Thanks!

 

[Curious Hound]

Some of this could be due to the fact that they are “used” parts. Wear patterns from previous use could be messing with you. I think that drive side pattern is pretty good.

 

[4x4junkie]

I have seen it mentioned a few times that (for the reason ericbphoto mentions) you want to focus more attention on the coast side when setting up used gears (coast side having less wearing-in). Your coast pic seems to indicate you need a (much) thinner pinion shim, but you're saying you've tried all the way down to 0.010 (meanwhile the drive pattern looks like an ever-so-slightly thicker shim could be used, maybe .002-.003" thicker), so I'm at a loss on this one.

Does the axle housing you're using have any past history (such as blown-up diffs, stripped gears, etc.)? Are the patterns (and backlash) consistent everywhere around the gear? How many miles are on those gears (if you know)?