Originally Posted by metalnut

Ok, so I met with my guru friend. Here are the results

1. His transmission cases also rocked side to side a bit, so he sanded down the middle portion that was the high point. That lets the cases rest on the points which the screws go through. I did the same but sanded the whole surface. I'll try using shims around the screw hols to separate the two halves a bit, starting with 0.1mm all around and going up if needed.

2. He believes he's using 0.1mm shim on the side of the gear diff, so I'll try that as opposed to 0.2mm. I tried no shim and the diff definitely spins more free, but the grinding noise of the gears is increased (since the ring gear isn't pushed over as much anymore, I presume).

3. We came to the conclusion that my top gear cases are deformed, specifically where the smaller/inner small bearing fits. I'll take pictures of this tonight. It looks like it's meant for a 9mm bearing, not a 10mm one. He's never seen that before, his were fine. I'll have to get new cases and hope I don't get ones from the same bad batch.

To summarize... I hope Tamiya releases aluminum gear cases soon. Charge $50 per set, I don't care, take my money.