Hyena

iTrader: (1)

For a change, a topic asking about a manual to automatic swap-


Long story short, an equipment failure at the workplace left me without the use of my right hand and arm for the foreseeable future- I'll spare the gruesome details

However, on the "bright" side. I've been compensated, and part of the arrangement includes modification to my vehicles to make them accessible for me to drive. I believe there is a limit for this at 9,500$ per vehicle, but I'll have to double check on that.

My main car has always been my RX7, I've daily driven it as a half-bridge GT35 for a few years now. Are there any automatic transmissions that I would be able to swap into the S4 T2 frame and engine? In searching I've found mostly swaps that are for all out drag racing for the most part, and I'm not really interested in a super high-stall race transmission, just something that will enable me to keep driving the car as I do.

Any direction or help on this is appreciated! I really would like to keep driving this car.

misterstyx69

iTrader: (142)

I can fully empathize with you.(sorry about your situation).

Have you considered something along the lines of a Automatic Gm trans,or even,I hate to say a v8 with an auto trans on it?
Mind you I am not sure myself about hooking a wankel to a gm trans,but I am sure it could be done.Lots of stuff is possible now..!I have seen a Wankel to VW trans,so I don't think the Gm trans is a far fetched idea.
Take care.

Hyena

iTrader: (1)

Appreciate it man!

I'll certainly consider whatever will work, I just don't know at where where to begin!

RotaryResurrection

iTrader: (8)

I would look to swap in a non-electronic GM trans like a 700r4 or turbo 350. Those have a HUGE aftermarket available to build them and make them behave just about any way you want, and any local redneck shop can build the heck out of one for you. Even a modified turbo rotary is probably not going to make enough torque to break even a stock one. The concerns would of course be mounting it to the engine and chassis, and making a custom driveshaft. Even with a nice trans fluid cooler/lines and some modifications, you should be able to accomplish such a swap for 2-4 grand even if you are paying a shop to do the work.

Tui

iTrader: (2)

Why not an automatic trans out of a JSpec TII?

satch

iTrader: (1)

This would be a good idea, but they are probably very hard to find.

RotaryResurrection

iTrader: (8)

As far as I know, the JDM turbo auto is the same as the USDM NA auto. There is the S4 version which is mostly mechanical and would probably be easier to swap in and make work, and the S5 electronic version which is controlled by a computer (ECAT) which would require the correct JDM ECAT computer. IF your car is an s4 then you might have a chance at making the s4 trans work.

The problem with them is that they are frankly just shitty transmissions. Even when they are "right" they do not drive like a "normal" car. They seem to shift at the wrong times, they respond slowly, sometimes they vibrate and cause our old interiors to rattle, and there is a lot of slip/slide between shifts. Since they are an uncommon transmission, there is no real aftermarket support.

But, if you are looking for the most direct bolt in swap requiring little to no fabrication, that is the route to go I suppose.

TonyD89

iTrader: (10)

I just gave an S5 auto away for junk. The only value in these seems to be the removable bell housing, which I kept. It appears to be very popular for fitting non RX7 transmissions to the 13B. I think mostly manual ones though. But the solution may lie in an auto with a removable bell housing and an auto bell housing from an RX7.

Hope that helps.

Copeland

iTrader: (42)

You could always just 20B it and leave the factory transmission on it. If you left it 100% stock you could do it $9500.

SpikeDerailed

iTrader: (7)

Im going to go with RotaryResurection and say adapting a common usdm atx like a 700r4 or c6 would be the best route. Lots of aftermarket and know how to make them shift well and at a rpm the rotary would be happier with, just need the right converter to make it drive decent.

Hyena

iTrader: (1)

Thanks for all the replies, guys! The GM transmission route seems like the one that would work out the best for a more high performance engine. I'm going to be going to a couple places today to see what might be involved with making either a bell-housing adapter plate, or if I can possibly make one between the bell-housing and the actual transmission "box" itself

Can the 20B automatic be mated to a 13b in any way? I imagine that transmission is a bit stronger.

RotaryResurrection

iTrader: (8)

The auto FD, cosmo 13b and cosmo 20b all use the same auto trans bellhousing pattern, which is essentially the same as the fc manual/auto bolt pattern. Those newer auto engines put the starter half on the engine and half on the transmission, so the engine's rear iron has a cutout and mounting flange for the starter...meaning you can't use any 93+ auto trans behind a 91 and earlier rotary engine.

I have a complete 89-91 auto trans equipped car if you need any parts from it for your swap...shifter, pedal, bellhousing, flexplate, etc.

The problem with trying to mate a GM trans behind a rotary auto bellhousing is that the GM/v8 style converter is going to be much bigger than the rotary bellhousing...so that wouldn't work either. You'll have to figure out a way to mount ALL the GM trans stuff onto the rotary block using an automatic rear counterweight from an 86-88 auto engine. The GM 700r4 bellhousing is probably 6 inches bigger around than the mazda one was (it's also a 1 piece case), so you'll need an adapter plate/spacer that bolts to the rotary block and has bolt holes for the GM trans.

RotaryEvolution

iTrader: (30)

a turbo350 would be more reliable than the 700r4, even though it has additional gears and more upgraded parts availability. the early 700R4 was total garbage, it was only until the mid 90's that they revised it to work reliably, so anything in the early 90's or prior would need a complete overhaul and upgrade.

i recall one thread about someone using the swap with a drag car, but i don't have a link.

the 350 is basically bulletproof in a 7, i've used them in cars nearly 50% heavier and with 400+ft/lbs of torque and not had any issues. there's no way around the adapter problem, if you want to put a real transmission behind it.

Tui

iTrader: (2)

I read the S5 TII was rated 200hp at the flywheel stock.

Anyone have an educated guess how many more ponies you could safely add running the stock Auto Transmission?

Hyena

iTrader: (1)

I would probably take you up on purchasing all the odds and ends items once I get a viable method all sorted out!

Transmission shops around here have a multitude of options for both of the GM ATXs, one quoted me a 700r4 manufactured and geared to spec for around $1200, or $1,500 if you don't bring in a core- apparently you can just bring in a recent dyno sheet if you have one and they will do their best to match the gear set based on that.

I'm waiting for a couple of machinist shops to get back to me as to what the ballpark might even be for making such a plate, one estimated around $600 while the other said $700+ I guess we'll see who pulls through on that. Both shops told me they can most likely make any of the adapter hardware that might be required between the engine and tranny.

That being said, I am assuming I'll need an adapter to connect the GM torque converter to the Mazda flexplate? Or would it be an adapter between the Mazda counterweight/e-shaft itself and the GM flexplate?

Also: for the drive shaft end of things, it is preferable to make the Mazda drive shaft meet with the tranny with an adapter, or should a GM shaft be used with an adapter at the diff side?

Thanks for all your help thus far guys, really appreciate it, and it seems like it's probably a real possibility of it happening without too much of a hassle

RotaryResurrection

iTrader: (8)

They barely hold up behind an NA rotary. Most original autos with 80-100k miles or more are mostly shot, with heavy slipping or entire gears that fail to work. Even when they are rebuilt, they are not really "right" and they still slip a bit between shifts and the shifts are very soft. This is with an engine that peaks at most 150ft-lb of torque.

Now add more torque to that, at lower rpm, and tell me if you expect the effect to be positive or negative with respect to shift firmness and overall longevity.

With that said, if you have an intake and exhaust on a turbo engine then the trans could probably live for a couple of years at least. IF you're talking 275rwhp then I don't think it would do well for long at all, especially if you plan to drive the thing hard at all for long periods (such as a mountain/canyon run).

Tui

iTrader: (2)

Thank you.

RotaryResurrection

iTrader: (8)

Might want to check in with finish line transmissions, they are highly spoken of on the ls1tech forums etc. that deal with domestic performance auto applications. But they are probably not cheap either.

It should be doable without a huge hassle IMO. The main thing will be fitment of the new trans into the FC trans tunnel....most domestic RWD transmissions are significantly larger than the mazda unit.

Your bellhousing, torque converter, starter, and flexplate all have to match. So those parts have to be all GM or all mazda. You'd probably be finding a way to make the GM stuff bolt to the mazda engine...you would accomplish that by using the 86-88 mazda automatic rear counterweight, which converts the tapered e-shaft end with one nut on the end into a standard flat 6 bolt flange that a flywheel/flexplate can bolt to. From there it is simply a matter of spacers etc. to get everything aligned front-to-back.

I have always been told by driveshaft specialty shops that if someone is willing to cut a shaft in half and use a stock joint on one end and a different joint on the other end, that you should run away from them. In other words, a purpose built shaft should be built from scratch, with the correct yoke, joints, and flange in place for the parts you will be using in your car. No part of the original mazda shaft should be reused if it's done right.