Diff Ring and Pinion Pattern

[Resident_Ranger]

Hello everyone, this is my first time rebuilding a differential(Ford 8.8). I was looking for some thoughts on the ring and pinion contact pattern. Its the original gears. They looked to be in good shape, but probably have a little wear. I'm thinking that is looks like the pinion is a little deep, but I would like some thoughts from other people with a little more experience than I have.

 

[spottedwolf]

Looking at the pictures you have I'd say they look pretty good. I added a general acceptable drive-side pattern image. As far as the noise it is probably wear on the axle splines. You cannot get a true reading by gauging gearplay with axles installed and driveline hooked up. Many times I had clients thinking their end play was too much from trying to feel it by the driveshaft. The 1st test I'd do was try to force the yoke in or out by hand. If it moves either way the backlash is off.

Ford recommends 0.008 to 0.012 inch of backlash. If you have too much backlash, you want to add side carrier shims to the driver's side and remove them from the passenger. Only someone with a lot of gearwork under their belt can do that and get a reasonable idea. Also...a differential that is serviced for a leaking pinion seal without replacing the old crush sleeve is another dance with potential failure. The best bet, if the pinion seal shows any oil, is a new seal and crush sleeve. That is not a job for the inexperienced.

 

[Resident_Ranger]

Thanks for the reply. I should be a little more detailed in my info. I'm rebuilding the diff using the original gears. I put new bearings and races in and set the preload on the pinion. It has 24-25inlb of rotational torque to continuously move it. I have a new diff, so the shim stack has changed. I'm pretty sure the shim stack preload and setting is good on the diff. I measured .010 of backlash. So this is where the pattern is after all that.

 

[Briansshop]

The original,or same thickness, pinion shims should be reused.

 

[Resident_Ranger]

The original,or same thickness, pinion shims should be reused.

My original pinion shim got mangled while pressing the old bearing off, but I did match the thickness with the new shims.

 

[spottedwolf]

OK Res.....so let's say everything else is within tolerance and the miles on the diff before you tore it down had been the cause of a pattern change originating in a worn crush sleeve. The movement of the pinion, in and out, would cause some uneven marking on it and the ring gear. The light scoring (marking) would correct itself over time from the look of your drive-side image. Your pattern now, when closely viewed should show the actual bare spot where the R&P were marked from the floating depth of the pinion....but once reset it won't be anything excess except, maybe, a bit of a hum/howl. Where the "slap" is I'll stand on the idea of axle-spline as an age-use issue.

 

[Resident_Ranger]

OK Res.....so let's say everything else is within tolerance and the miles on the diff before you tore it down had been the cause of a pattern change originating in a worn crush sleeve. The movement of the pinion, in and out, would cause some uneven marking on it and the ring gear. The light scoring (marking) would correct itself over time from the look of your drive-side image. Your pattern now, when closely viewed should show the actual bare spot where the R&P were marked from the floating depth of the pinion....but once reset it won't be anything excess except, maybe, a bit of a hum/howl. Where the "slap" is I'll stand on the idea of axle-spline as an age-use issue.

So all in all, is that a "run it, it might howl a little but it will be fine" or a "I should probably take it apart and shim out the pinion some more" I guess I'm just looking for some solid direction at this point. The axle splines were definitely worn. I was thinking I was going to reuse them up until last weekend I gave them a good go over and found they should probably be replaced.

 

[Briansshop]

If you used the same thickness pinion shim and got the BL in spec, the set up should be at least as good as it was. Factory install before?

 

[Resident_Ranger]

If you used the same thickness pinion shim and got the BL in spec, the set up should be at least as good as it was. Factory install before?

As far as I know. I suppose I'll run with it and see how it goes.

 

[4x4junkie]

Used gears are usually harder to get a good readable pattern on. It's said you want to put more attention on the coast (or non-forward-driven) side of the gear when resetting used gears (due to less wear on that side), and yours looks pretty good there (it may be a tiny touch deep on the pinion, but probably not enough to warrant further messing with it).

FWIW, Ford specs the backlash range: 0.008-0.015" for the 8.8".

 

[spottedwolf]

So all in all, is that a "run it, it might howl a little but it will be fine" or a "I should probably take it apart and shim out the pinion some more" I guess I'm just looking for some solid direction at this point. The axle splines were definitely worn. I was thinking I was going to reuse them up until last weekend I gave them a good go over and found they should probably be replaced.

Res buddy....I'd double-check your backlash and plop those newer axles in there and run her hard a bit before I'd rethink the pinion depth becuz...if she is scored off-pattern that bad the howl will just get worse in 5-10 thou miles. If it's just a bit it will still work well. Have a look at your side gears if you go for a total redo.
and.....Junkie's view works in the same way.