Has anyone attempted to put a FC Rear subframe in a FB???

 

No. Not possible w/o a mountain of $$ and skills. Not worth it.

 

Thats a closed minded reply. Of course its never been "succesfully" done. But has anyone ever tried? What was their wall? why couldnt it be completed? Answers to these questions may or may not show it can't be done.

 

miata rear would be a better choice.....posssible.... time and money

 

its deffinatly doable imho but skills would be imperitive would probably be easier to not use the full subframe and fabricate alot of it yourself

mounting the diff itself wouldnt be that difficult (i dont think) it would be the suspension and hub assembly that would pose the most threat to failure

 

It's not a closed minded approach. It's not worth it.

https://www.rx7club.com/showthread.p...&highlight=IRS

 

There were mazda test cars with fc rear ends, and a forum member swapped the miata rear a few years ago. A local here had the FC rear stuffed under an FB with marginal success (read half assed).

It really all depends on how much time/money you want to sink into it. If you are determined to have IRS in your FB, don't use the FC bits, opt for something a little more modern with better handling options.

miata swap= https://www.rx7club.com/showthread.p...light=irs+swap



FD bits (i know nothing else about this car)

 

I got a few pics of Miata subframe in a 1st gen. I planned on putting a t2 rear in a 79 a while ago... Maybe ill do it in the future still.

It's really not all that hard if you can weld and measure.

 

WOW!! The miata subframe swap looks MUCH easier... As of right now I have a FC Subframe. I can measure, Cut, Weld, And i'm thinking about attempting to put it in my FB.

 

Just an honest question. Why would you want to swap it? The FB rear end is actually pretty awesome lol. Its a LOT lighter assembly, and the watts link is a pretty good rear end suspension set up.

 

I want more options. I have a FC that Im tearning down and Im swaping the FC front subframe into my FB.. I plan on running a set of coilovers, and I would love to run the other pair in the rear. But most of all the IRS.

That and I like projects..

 

You can cut, weld, and fabricate with metal - Anything is possible.

 

For all the time and work it'd take, why not just fab a proper race-spec rear end? It's not like the FC rear "almost" even fits or is even really very good. You're essentially starting from scratch.

 

Even if you succeed, you're still stuck with the passive 4 wheel steering. Mazdatrix sells bushings that eliminate this problem.

When I was at the salvage yard yesterday, I noticed a complete FC rear end on the ground next to the car and yes, the thought of putting it in my FB made me look closer. I didn't see any easy way to do it in my five minute quick check.

 

The front FC cross member and rear subframe were first tested by Mazda on 3 FB engineering test mule cars for track testing. 8 color pictures of test mules and details on suspension installation.
FB vehicle designation X-0, X-1 and X-2
See pages 121-123 RX-7: The New Mazda RX-7 and Mazda Rotary Engine Sports Cars (February 1986)
Jack K. Yamaguchi (Author)
ISBN-13: 978-0312694562

 

[QUOTE=rx7lives;10971084]Even if you succeed, you're still stuck with the passive 4 wheel steering. Mazdatrix sells bushings that eliminate this problem.

How am I "stuck" with the 4 wheel steering if Mazdatrix sales bushings to eliminate the problem???

 

The Miata rear suspension is a better piece. If you want to do an IRS that is the better direction. Doing an FC or a Miata rear suspension swap is going to involve allot of fabrication so might as well start with a better part.

 

I wonder how hard it would be to get a miata subframe??? I live in a po dunk town.. Portland oregon is 80 miles away, But all the u pull it places there say I cant take subframes off!!! (Saftey hazard)

What kind of crap is that?

 

Go with the FC subframe for one main, but very crucial reason...

The Miata rear is not any stronger than the 1st gen rear. They are both 7" ring gears. If you go with the FC sub-frame, you can always get a TII rear for it which is a very proven stout rear.

They are also much easier to get a hold of and most likely cheaper.

 

If I was doing an irs swap with factory parts I would think hard about R180 subaru STI stuff, or late model toyota cressida/supra stuff.

 

Cost is the biggest issue for me.. I blew up another turbo motor so...
I bought a 88 RX-7 For $900 It has a good running N/A engine, And has the 5 lug hubs 4 piston front breaks and a LSD.

I thought I would do the FC subframe swap and throw the N/A 13B in there untill i build my next turbo 4 port.
So now Im left with a fc rearend that allready has 5 lugs and a good working LSD.

The fabrication seems like the cheap part.. I have all the tools and the time to do it. What I dont have is cash to drop on a miata rearend or a STI rearend...

Plus I am buying a set of Ksport coilovers to put on the front, And it would be vary cost effective to use the rear ones as well.. If i put a miata rearend in the car then I would have to buy another set of miata coilovers just for the rear..

Can anyone tell me what the differences between my rearend and a Turbo II rearend???

 

The important difference is the ring gear size. 7" for NA, 8" for TII... PLus the axles are thicker on TII's. Also has more stout stub shafts. Just an all around better option. And lucky enough, its a direct bolt in swap for the NA rears in the subframe, which are identical.

Bigger is better here.

As is the same for solid domestic rears. Ford 9inch is stronger than an 8.8. Which is stronger than the ford 8inch. ect. ect...

 

the T2 diff and the miata diff ears are the same, so you can put a T2 diff right into a miata....

IMO, the miata suspension is better, and it would fit the FB more easily

the FC suspension isn't that great, especially for drag racing, and doesn't fit the FB very well, so its a lot of work, for questionable gain....

 

Good to know! Thanks for the info.. Im going to have to do some research on ratios now..

 

Questionable gain.... ??

I dont drag race the car.. (well like once a year) so it seems like a hands down upgrade/gain to me...(IMO) That and I think I can make the subframe fit for less then $100. metal, cut off discs and welding wire doesnt cost that much..