Dick, the pinion length/depth is critical for the gears to operate properly. If the pinion depth is out of spec enough the gears will experience accelerated wear, and be noisy. I have seen many problems in this area. This is something you need to check out soon, or the gears might be damaged. Most of the time gear manufacturers only allow as little .002 inches, or .050mm during installation. If you are out .1mm or more you can get accelerated wear, and noise.