RB7 gear diff build

[Mark Boos]

I watched the video from Team Wells Racing on YouTube about building the gear diff and decided to change the original diff gears to the LAW50 diff gears, too.
No I have the problem that when I tighten down the screws from the diff cover the diff gets stuck and doesn't move. I put the original gears back in and everything is fine again.
I measured the gears and found out that the large gear from LAW50 has about 2,5mm thickness and the original one has about 2,3mm thickness.
So how can you get the LAW50 gears to work on the Ultima gear diff?
Thanks!