Project Ruze The UK's first all-Japanese RX7 V8?

Gearbox

The gearbox I’ve chosen to use is a late-spec R154 with a remote shifter from a JZX90 Chaser. Tech2 tell you to get a gearbox from a MK3 JZA70 Supra, but any gearbox from one of those is going to be 20+ years old, and they are a slightly weaker design than the later box. Also, the shifter position is much further forward, so you have to cut and weld the shifter. I can’t weld so that’s a no go straight off!

I bought my box from a front-cut someone was breaking on Driftworks. The flip side to using a JZX box rather than a JZA is that they are 3x the price! But it arrived next day on a pallet (which was just dumped outside the door of my workshop unit – wtf!) and with a warranty.

IMG_20120802_122321

 

 

 

The box came with the rubber mount & crossmember from the JZX which were no use to me as the Tech2 rear mount is designed for the JZA rubber. I ordered that part from Toyota, with new bolts:

1JZ-GTE_Supra_90

 

 

 

1 x 12371-42020
4 x 90119-08684
Now as you can see in this diagram (gearbox mount is at the bottom) and the following photos, the bolts in the top of the mount that attach to the gearbox are offset. So you can position the gearbox further forward or further backwards in relation to the crossmember depending on the application. Obviously further backwards is better for weight distribution, and actually a requirement in this particular case as with the gearbox mounted in the further forward position, you couldn’t get into 1st, 3rd or 5th as the shifter made contact with the transmission tunnel.

gboxmount_wrongwayround  IMG_20120914_191231
Wrong way round – Gearbox sits further forwards

gboxmount_rightwayround  IMG_20130502_203715
Right way round – Gearbox sits further backwards!

I don’t know which way round Tech2 want the mount, but I suspect it is with the gearbox positioned further forward. You can see there is even a 3rd hole towards the back of the box, meaning you could mount even further forwards. I make that 8 possible combinations!

Changing the gearbox position to be further back meant that the propshaft was too long. However I’m changing the rear end to a diff from an automatic RX7 which has the companion flange slightly further back than the manual diff. It’s only about 15mm but every little helps! You have some further adjustability in the gearbox end of the prop as the sliding joint can slide quite far into the gearbox.


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I'm the one actually trying to build this thing!