Hi all, trying to get a new box built for the autocross next weekend. My son just got his license and its going to be his first event driving so its inspired me to finally build a new box and fix the wonky shifting I've been putting up with for the last couple of years.

I bought the doctor's DVD set for rebuilding the gear stacks and I think that all went well, but now I'm trying to put my new (to me) Guard differential . Yeah, I know. My wife said the same thing, "You're doing that for your son? Sure." Anyway, to preserve pinion depth, I carefully measured the intermediate plate gaskets that came off the old box and installed new ones out of the gasket kit that closely matched them.

I've checked everything I can during the diff swap. I measured the dimension between the bearing seats on each diff and they were within a couple of thousandths of each other so I put the same bearing preload spacers on the same sides as came off of the old diff. After installing it I measured the bearing preload per this thread (ring and pinion set up) Both torque and gap between the side plate and case measurements were within spec. I also checked backlash per the previous referenced thread. It is 0.008" which is slightly higher than the target 0.007".

So, as a last check I put gear paste on the ring gear, put some resistance on the CV flange, and rotated the ring gear through three full revolutions using 1st gear and turning the input shaft. I went three full revolutions in each direction to get a good pattern on the drive and coast sides of the gear. This is where I ran into a question. The pattern covers the whole face of the gear on both the drive and coast sides. Most references show the ideal pattern to be a central high pressure area that tapers off near the edges of the gear face. And, all references for how to adjust the pattern show how to move the high pressure contact area around the gear face but I never saw a reference to a full face pattern. Is this bad? What needs to be adjusted? For what its worth, the wear pattern on the gear face appears to be full face, just as the gear paste is showing for the new installation.

Am I over thinking it? Is this okay?
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I've never checked coast and drive at the same time. I put marking compound on 3 or 4 teeth and rotate one way against a load, clean it all off and repeat the other direction. You might be messing up your pattern (if I read that right).

I don't think I've ever seen the "textbook" pattern as clear as they show you.

Ooo. Good thought. I hadn't considered that.

A quick test in situ and the pattern on the drive side didn't change meaningfully, but it was clearer to read. The pattern is essentially unchanged. It still covers a vast majority of the tooth, but is clearer that there is more contact near the toe than the heel of the gear face.

I think I was expecting to see a pattern that was very clear like you see in the books. I think I'm going to run it and see if there is any howling. I'm just trying to be uber diligent given that the Gaurd is in there. I REALLY don't want anything to come apart and send debris through it.