Stuffing a FC rear end in a FB
 

Hey guys,

So I bought a FC For $900. mainly for the engine and front subframe for my FB. I dont want the rear end to be scrapped with the rest of the car. So I have decided to Stuff the FC IRS under my FB.

Reasons for swap:
1. I Already have a compleate FC rear end and all the goodies to go with it.
2.Gives me 5 bolt wheel lug
3.Big rear brake upgrade
4. I will be able to use the rear coilovers from the set ill get for the front.
5.I will be able to upgrade to 8 inch ring gear when I get a turbo diff and shafts
6. Upgrade to independent rear suspension.
7. More options

Im starting the swap today so I will update tonight.

Good luck mate.

Will be great to see and FB sitting with rear wheel camber!

From everything ive read its possible but extremelyyy hard due to going from a solid read to a live axle. Goodluck with it man. Im lookin forward to seeing some progress pics.

Allright,
Today I pulled out the straight axle, And started sizing up the diff and the subframe.
I think the best way to do this swap is to use bits of the FC frame to ease the mounting of the FC Drivetrain.
The diff mount was easy. I used the diff mount from the FC. I cut it to size so It fitt right inbetween the FB rails. After some careful measuring welded it in place, Then welded 1/8 inch steel brackets on the sides to reinforce it.

I'm glad someone has finally decided to go through with this swap, and post pics, I'll be watching this thread! :)

I soooo wanted to do this but wimped out!

Best of luck, I'll be following this for sure.

awesome cant wait to see the end result.

Right on! Thanks for the support guys! :)

I Just got off work. So im going to get to work on the FB.
I'll update tonight on what I get done.

There was a local car in the scrapyard here with an fc swap, its not going to be as hard as most people think. You are off to a good start, keep it up.

Isaac

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Today I mounted the subframe mounts. I cut the subframe mounts out of the FC and started the size them up the the FB.
After getting a good idea of where they are going to be mounted in the car. I started cutting big chunks of my car out (Got a little to cut happy I think).
Then I Bolted the subframe mounts to the subframe and did the tedious task of making sure I had the subframe just where I wanted it. Then tack welded them in place.
I measured again after tack welding them, Then I started some sheet metal work.

staying tuned in

big thumbs up

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i will be watching this with great anticipation............

^ You see why I am selling the GSL-SE and the GSL rear ends now..highnitro :) ^

So today I got some more sheetmetal work done on the subframe mounts..

After getting some more sheetmetal holding the subframe in place I mounted a control arm to see what kind of clearance im going to have to make for them.. More then I thought.

I have to cut out such a large chunk of the frame rails that im going to have to make a new set of framerails.

Hey guys,
So I Got some beefy 2x3 steel tubing for the new framerails.
The new framerails go "Inside" of the car at this point, Then go through the floor where they are welded onto the stock rails. Did a little more sheetmetal and called it a day.

With the use of a "angle finder" and a "contour gauge" the fab work wasnt bad for the rails.

hmm since you have to do so much fab work, you should put the control arm on the subframe and look at where you're at, in an FC lowering the car gives you more negative camber than we want, but since you're performing surgery, you can fix this by moving the subframe UP in the car, which is the ideal fix to the problem.

Yeah I did think about that, Cuz I do plan on lowering it..The subframe is as far "up" as I would want to go. Anymore and it will require a lot more fab work.

I was reading about the "camber bar" racingbeat and mazdatrix sells, and how it tilts the subframe to adjust camber..

The tech at racingbeat told me that if you can dimple the "frame" you can get a lot more camber adjustment out of it.. So I left plenty of room so I can get the most out of the camber bar.

Since the bar adjusts camber by tilting the subframe. couldnt I andjust camber by tilting the subframe mounts in the car???

I had no kid today, So I spent all the time I had on it today.
I got a bunch of the sheetmetal work done. The subframe mounts are pretty much done..
Cant wait to get started on the strut towers.

Wow, I really want to see this completed. The solid rear end is the only downfall in getting the FB to handle properly. This is going to be interesting.

Well, The landlord stopped by and told me he wanted the car off the jack stands asap. So I put a lot of time into it to get it on the ground..

It's not done by any means, But it is on the ground.

More pics!

This is FREAKING AWESOME!!

GREAT JOB!!

THANK YOU!

I am having few issues though. I am have a lot more trouble finding a turbo II driveshaft then I thought I would.
It's either that or buy a N/A clutch and flywheel and use the N/A tranny and driveshaft that I already have.

At any rate Ill have to wait a while for funds. This swap cost me real close to $200, But now I can sell all my Turbo II swap into a FB stuff :)

Wow, that is awesome. I can't wait to see what you think of the handling now.

All you need is a driveshaft yolk from a second gen automatic. Same yolk as the TII, but uses the same u-joint as the 83.5 to 85 first gens. No need for an expensive custome driveshaft.

Im pretty sure the stock turbo II driveshaft will bolt right up.. There is no part left on the cars drivetrain that is first gen.

Isn't the diff you're using an NA? If so you'll need the NA yoke.

In either case that is looking great, really nice work! Looks like it belongs there :)

If the rear center is NA, just use the entire automatic driveshaft. That will work!

That is sweet!!! I had no clue that the automatic driveshaft had 23 splines.. That and I wasnt sure if the rear diff used a different flange between N/A and turbo..

So if a FC guy swaps a turbo II tranny in his N/A car he just has to get a automatic drive shaft and he is basically good to go? Thanks for the info guys!

I Did a bit of research and found out the automatic driveshaft is close to two inches shorter. Has anybody had trouble using this setup before? Like bad vibrations or anything?

well it depends, whats the length between your tranny and diff? are you positive its the same as a 2nd gen?

You have a very good point.
So, As soon as it stops raining Im going to crawl under there and take some measurements.

So I did some measuring today it is about 35.5 inches from the diff flange to the end of the transmission tail housing. So Im guessing the automatic driveshaft is out of the question It being 35.94 inches long. The turbo/N/A length driveshaft(38 inches) looks like it will be a great fit.

OK so here are my options.
1.Get custom driveshaft made.
2.Install turbo diff, halfshafts and turbo driveshaft.
3.Get N/A flywheel and clutch. Then use the N/A transmission and drive shaft I already have.

I think its time to start looking for a clutch and flywheel.

well this swap looked rather straight forward. I considered it for my rally car. perhaps ill go through it it. I just really do not like the pin mount for the struts. I have thought about using a toyota mk3 supra assembly instead.

or go four link...

Just get tII trans, diff and shafts. The NA stuff is fairly weak. The transmissions are only designed for NA, they cant handle much hp. You'll shear the teeth right off the gears. The diff's are okay, I havent heard too much of them grenading. Your going to end up swapping to TII stuff anyway, might as well do it now.

The swap was pretty much straight forward. Everything kinda fit right in, Besides the subframe mounts.

I havent driven the car yet, But I would recommend this swap to anybody that can Cut, measure and weld. The most metalworking I had under my belt before this was a welding class and I made a couple exhaust systems.

It did cost close to $200 Dollars(Sheetmetal, cutoff discs, welding wire, Seam sealer Etc.) and quite a few man hours.

I would do this swap again.

good trade?
 

Tell you what. You swap my rear and I'll swap your front! :nod:

I will be doing this swap in the future. You made it look easy. Good job!

Ooops! I lied in that last post. I forgot to mention that I did a FC front subframe swap as well. But The front end has a bad ride hight issue.

Frankenmazda your car is AWESOME!!! (IMO)A IRS setup would really set it off!

well you convinced me to try it i think.

how much suspension travel are you getting in the rear. especially with out the sway bar.

The sway bar is installed.
This is the only part on the FB that will limit suspension travel, and the only part of the FC rear end that would make contact here is the "lateral link".

The way mine is setup right now the tire will bury itself into the fender well before it will run out of suspension travel.
Im sure if I went with a smaller diameter wheel/tire It would still bury it in the wheel well before any suspention components would make contact.

ride height
 

Looks like you are going to have to ditch the springs and go to a coilover setup. You can also raise the strut towers. I raised mine 2 inches but the hood hits it so you have to deal with that as well. An inch or so will clear the hood.

I would love to add a FC IRS but for now I just want to drive it! Maybe a future winter project.

Can't wait to see yours finished.

I'm a huge fan of your car!!!
I LOVE what you did with your front strut towers!!! I am going to do that myself(but only one inch).

I am going to get a set of coilovers, But its going to be awhile. Im a single dad with a four year old and I work at home depot.. So its a major "budget" build..:)

Would you happen to know how wide the fc assy is wheels mounting space to wheel mounting space?

RE-Turbo FB - Just wondering how this setup holding up?. :)

This is awesome .. keep us posted on how thing are going with the FB

Im curious to see how much it weighs!

great job!! i've been seriously wondering about this idea. you may have just helped me with the last idea for my se. props to you. :icon_tup: