Tailhousing swap

Here we will be talking about another option to retain the factory miata PPF. For this section, you will need:

  • Rx7 N/A Smooth Case Tranmission (images below)
  • Miata 5 speed Manual Transmission (images below)

To be successful, you will want to avoid the “ribbed case” transmissions:

  • T2 Transmission
  • FD Transmission
  • Rx8 Transmission
  • ND Transmission

The TURBO transmissions and N/A Transmissions are NOT interchangeable. Please see below Turbo II and FD Rx7 transmissions, these will NOT work for a tail-housing swap.

Getting Started

From what I’ve been able to gather, Mazda stuck to 2 main designs for the transmission from the RX7 and the Miata. There is a “Smooth Case” transmission which was available for RX7 from ’79-92 non-turbo, and Miata NA/NB transmission:

Miata NA Transmission Picture
Miata Transmission (Note: PFF mount on the tailhousing section is on the passenger side of the transmission.

Below are a few picture of the smooth case rx7 N/A transmission

As you can see, the center chunk of the trans is the same as the Miata 5 speed transmission. BUT, there is not a PPF mount.

Effectively, you will want to remove the miata trans tail housing, or you may be able to buy one separately depending on your situation. There are several writeups on this on the internet, but here is the manual transmission overhaul factory service manual from mellens.net for your reference when disassembling.

1991_manual_transmission_overhaulDownload

Mainly, what you are looking to get here is the following component off of the miata transmission and reinstall onto the 13b bellhousing tranmission, in doing this, there may be a few components to swap over from the other gear stack, but since I went a different route with my swap, I can’t speak to the intricacies, but fortunately, the above factory safety manual should be very helpful for you.

Reference Material:

Some the content for this page is taken from: https://grassrootsmotorsports.com/forum/grm/mazda-rotary-transmission-knowledgehelp-my-engine-/121494/page1/

Also a great reference is the following video from Castellaw Speed:

1991_manual_transmission_overhaulDownload