Crunchywaffle

I am looking into building a turbo engine and throwing it into my 87 base. problem is money is tight and so is time so is it possible to keep the NA trans, driveshaft, and diff while running the T2 engine?

From my understanding the clutch and flywheel are different but what else am I missing?

WondrousBread

Clutch and flywheel must match the transmission type and series of engine.

Eg. S4 T2 engine with an NA transmission needs an S4 NA flywheel and clutch, or an S4 NA counterweight if you want to run an aftermarket flywheel.
S5 T2 engine with an NA transmission needs an S5 NA flywheel and clutch, or an S5 NA counterweight if you want to run an aftermarket flywheel.

Make sure the counterweight (or flywheel, since the stock flywheel includes the counterweight) matches the series of engine. S4 to S5 have different rotor weights, so if you use the wrong counterweight you're going to have a bad time.

I've also never tried it myself, but I have a T2 transmission ready for when I need it and it is a lot beefier. I don't know how much power you intend to run, but I wouldn't expect a lot of longevity from the NA transmission if you want to launch the car or drive it hard. Maybe someone else will have more info on what sort of power you can expect to run safely on an NA transmission.

If using the NA transmission on the T2 engine, you can keep the NA driveshaft, diff, and axles as normal. If you swap to the T2 transmission, you need a custom driveshaft if you want to keep the NA diff and axles. Basically, you need a T2 drive shaft with the rear flange swapped to the NA one. The T2 transmission also has a different slave cylinder. If you want to swap the whole drive-line, you need the T2 trans, T2 driveshaft, T2 diff and T2 axles. The T2 axles are shorter and stronger.

EDIT: To clarify, I believe clutches are the same between S4 NA and S5 NA. But the flywheel must match the engine series, and the clutch must match the flywheel. You cannot, for example, run a T2 clutch on an NA flywheel. Diameter is different.

Crunchywaffle

Ok so flywheel and clutch match transmission, but what about running NA rotors. I match the counter weight to the series and type of the rotors right? I guess I could have asked if the NA trans will bolt to the S4 T2 rear iron without a problem.

I should have clarified I was keeping NA rotating components

WondrousBread

The T2 bell-housing has the exact same bolt locations as NA, so the transmission bolts up exactly the same. Forgot to mention, T2 has a different starter, so you'll need that too of you use a T2 transmission.

The rotor weight and counterweight matching is by series, not by turbo/NA. So Series 4 NA rotors are the same weight as Series 4 T2 rotors, and use the same counterweight. Same goes for S5.

So:

S4 counterweight > S4 NA rotors OR S4 T2 rotors

S5 counterweight > S5 NA rotors OR S5 T2 rotors

See this handy chart about rotor weight from Mazdatrix

Crunchywaffle

Awesome, I think ive got the info I need now. Thanks a bunch!

Rotary Alkymist

One thing you should keep in mind is that the gearing will not be ideal for a turbo. The gears are a lot shorter on a turbo tranny so that you come into the next gear at a higher rpm to keep the turbo happy. Also, if you plan to drive it hard it's only a matter of time before it blows.

Edit: If you had the opportunity to try both setups you would definitely choose the turbo tranny hands down. I get it though, sometimes you gotta work with what you have.

rx7racerca

iTrader: (1)

The NA trans (and diff) apparently work okay with stock-ish T2 power levels; I believe Aaroncake ran an NA trans and diff initially in his project TIINA conversion of an NA engine to a custom turbo setup, but it didn't last terribly long before both broke (mind, at 350+ hp levels, iirc). I seem to recall the NA trans is okay with 200-250hp, much like the Miata's, but even that is really more than it should handle for long life.
I couldn't find Mr. Cake's build threads (too many references for search) so maybe go here My RX-7: Project Tina

Crunchywaffle

I don't mind having to replace it in the future, as long as I can daily my 7 again for awhile I'll be happy Ultimately I do want to do a full T2 swap or maybe even an Rew. trying to find the turbo parts I have was a mission on its own, I cant imagine finding a decent t2 trans is any easier. Thats a job for when the snow is back.