Miata gear swap

[infernosg]

I guess no one on these forums has done this swap?

I spoke with Mazdatrix about this and they basically answered all my questions:

1. They don't swap the mainshaft to retain the harmonic balancer and they haven't noticed any negative effects.

2. They swap the 5th/reverse housings (called the intermediate housing by Mazda). The exterior designs are similar but there are quite a few differences internally. To remove this housing from the RX-7 assembly you have to remove the harmonic balancer, which requires removing a ~2.5" nut with a special tool. I forgot to ask about the bearing plate but I assume that's kept from the Miata. They should be essentially the same anyway.

3. The only way to remove the input shaft is to disassembly the gear set down to the mainshaft. This involves disassembling the 5th/reverse gear set and separating the main and counter shafts from the bearing plate. There are several bearings/large nuts that need to be removed that require special tools from Mazda.

I'm going to attempt to tackle this myself and turn this into a "how-to" thread as I wasn't able to find any others out there. The hardest parts are going to be removing the bearings and large nuts without SST's.