Determining Wear Pattern
First lets get a quick understanding of which side of the ring gear tooth is the drive side (and therefore most important in our determination) and which side is the coast side.
|If you look at each individual tooth, you'll notice that once side of the tooth is shorter than the other. This is the COAST side, with the LONGER SIDE BEING THE DRIVE side. Our main concern is the drive side of the tooth.|
1. Using a small brush, brush a very, very light coat of gear marking compound onto three teeth of the ring gear at three different points on the ring gear. Do not brush the compound on heavily, otherwise a wear pattern will be difficult to discern. A little bit of gear marking compound goes a very, very long way.
(I cannot stress enough how important it is for you to use a light coating of compound on the ring gear. This was the first mistake I made and it cost me valuable time.)
Brush a light coatng of the compound onto three of the ring gear teeth, rotate the ring gear 1/3 of a full turn, coat three more teeth, then repeat one more time so that three separate areas of the ring gear are coated with (again, a light) coating of compound.
2. Rotate the ring gear in the forward and reverse directions until a discernable wear pattern is displayed on the drive side of the ring gear teeth that have been covered with the compound.
You will have to rotate the ring gear a good number of times in order to get a good determination of how the ring and pinion gears are meshing. I'd say you are going to need to turn the assembly at least 15 times in each direction. You may get away with fewer turns - I did not and I wasn't risking anything.
3. Read the pattern worn into the gear marking compound.
If you've followed my cautions regarding the thin coating and 15 or more rotations of the ring gear you should have an obvious pattern worn into the compound. There are a few sites that offer charts which can help you diagnose the meshing of the gears (Richmond Gear's website is one.) I decided rather than have you rely on the charts that I'd add some shim, get a pattern and then take away some shim and get another pattern so that you might get a better idea of the relationship between pinion shim and wear pattern.