I got a 9" rear in my Model A sedan behind my flathead. It had 4:11 gears in it, they were a little too much gear on the high way. I bought a set of 3:50 gears figuring it should drop the rpm's a few hundred, I do have a t5 in the car also. So I did my first ring and pinion set up. I got the instal kit with the new bearings, shims, bolts and everything else needed. Got everything set where I think it should be, backlash is .008 and pinion is shimmed where I think it should be. So I was looking for an experts opinion on how the pattern looks. Thanks
Make sure to set required preload on the differential adjusters. I killed a 9" gear set by not getting that right.
I would try it The contact line in the tooth looks kinda straight and you would like to see it curve up to meet the line that would cure down. Say to make it look like a foot ball if that make since.
Shim the pinion out about .010", reset the backlash to .008" and see how it looks then. The contact not be hard o top or bottom of the tooth on either member.
It had a .021 shim in it originally. I started with that one first. I thought it looked like the pinion was out a little too much. I swapped it with a .010 and that's what the first set of pictures were. Think I should try a .015 shim and see where that ends up at?
The concave side of the pinion (convex of the gear) is the side you want the best looking, since it's the drive side. The picture with the .010" shim is still a little too deep on the gear drive (convex) side. I'd try it with a .005" shim and see what the drive side looks like. The coast side looks good, but that's only used in reverse, so it can move up a bit further without any problem. Are you sure you reset the backlash? That will affect the contact pattern and move the contact toe or heel depending on too much or too little backlash.
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