[blacklabzeke]

I am setting up a GM 12 bolt truck rear with Richmond 3:73 gears. I have the pinion depth set at 2.8235 and the backlash at .0095 (Gear specs are 2.823 on the depth and .010 on the BL). I run the pattern and it seems a little high on the face of the drive side. Any suggestions? I will attach pictures

[jakeshoe]

You need a thinner shim on the pinion.

[richard stewart 3rd]

Hi,
I think you need to move the pinion
deeper in toward the diff. carrier,
add pinion shim.
Good luck,
rich
PS I think you may need to move the ring gear a little
farther from the pinion also, as it looks like to much tow
contact

[jakeshoe]

The pattern already appears to be oriented more towards the toe of the gear, if he adds shim and goes deeper towards the carrier, it will get worse.

It needs the pinion to be shallower to bring the pattern more towards center of gear and it should get deeper towards the root of the gear at the same time.

[jakeshoe]

The coast side looks OK though, the drive side looks like it is off by quite a bit to me.
Did you put resistance on the carrier when spinning it for the pattern?
I usually press my hand firmly on the rear facing portion of the ring gear/carrier while turning the pinion yoke so I get good resistance and pattern read.

[blacklabzeke]

How much shim Should I remove? I only have .028 behind the bearing now.

[jakeshoe]

Did you load the gear to get the pattern?

Be sure the bearing is pressed on good.

I would take out .004 and see where it lands.

Also be sure you clean all the compound off and start over. You have some dirt that is messing up your pattern.

[richard stewart 3rd]

Hi,
try here for differential & gear pattern interpretation,
http://www.drivetrain.com/ringpinioninstal.htm!
rich
PS I tried the address above & it won't connect
so www.drivetrain.com
then on the left in search box,type in, ring & pinion install

[blacklabzeke]

Yes, I did load the gears while checking the pattern. I am going to clean and check again. I thought if target pinion depth and backlash were right on the gear pattern should be right on too.

[lmsport]

Numbers generated by the lapping process cant account for the machining accuracy in your housing, which is why there are shims involved. The drive and coast patterns are close to the same radial point on the ring gear which means the pinion depth is very close. Your patterns is actually pretty good for a Richmond gear as they dont have a pattern like a stock gear, run hotter in a street car and are prone to noise. Gain some backlash and the drive and coast pattern will move to the heel.

[GMC boogie]

Pinion gear is not deep enough. Change the pinion shim out to a .035 and readjust backlash. Trust me,it will look better. You may need to adjust .003-.005 from there.

[blacklabzeke]

I changed the shims from .028 to .035 and the contact pattern is moving closer to the root of the tooth so I am getting there. I will post new pictures when I think I have the right pattern.