Has anyone done a 3rd gen rear axel swap? Im gonna be doing the 13b-rew swap, and was just wondering if this swap had been done as well.

 

Heh,heh............

The 2nd gen IRS swap is about the most asked question here,and no...its not an easy or feasible swap.It may have been done by someone,but at substantial cost and difficulty.The FD rear is basically the same work involved and more costly to get parts for.The TII rears are quite stout and cheap/easy to obtain.
The whole IRS system is vastly different than a solid axle rear.It requires different pickup points,torque mounts.....everything.

 

is it even worth it?
yea either go with TII or yer original, should it be in good shape

 

The stock FB axle can be made to handle very well and its capable of holding a fair amount of power too.
In a nutshell,if you have to ask if an FC or FD rearend can be put into a 1st gen.......then your not ready or able to perform the "swap"....if you can call it that, since it would be more like an undertaking of the 3rd degree, than a swap.

 

Doing an irs swap on a first gen would be along the same lines as cutting off everything in front of the firewall and going tube frame.

On the rear swap, not only would you be cutting out the entire middle of the rear body, including the wheel frame arches, then you would have to deal with the fuel tank location.

Unless you are putting out over 300 hp and doing many hard launches, the stock rear will hold. If you need more, go with a Ford solid axle.

 

I was just wondering if anyone had done this swap at all. That way I might be able to get some pointer's, or clues. Im going to be making this an all out kick *** mountian driving, track car, and want everything to be just perfect. And since Im going to be swapping in a 3rd gen front en, might as well as do the rear right? So you ask why dont I just buy the 3rd gen..... well I dont have $20K up front for a decent one, and since Im just doing this car on the weekends being paid for with me second job I really dont care how long this is going to take. All I know is that I do not like the Watts rear end, I do not like it Sam I am!!!

 

How's your fabrication skills? The 1st gen was used by the Mazda engineers as a test mule for the FC suspension, however, no one seems to be able to find any data or pics or tech papers on it. Afaik, no one has done the swap, FC or FD.

 

If you decide to tackle it,be prepared to lay the car up for a while,and buy some fabrication tools like welders,chop saw, and such.
Since the car is unibody,the shell has to support and absorb the torque from the drive and the suspension action as well.The IRS setup mounts the differential directly to the body and uses multiple torque arms to support the two ends where the suspension and brakes are mounted......couldnt be more different from the simple 4 link/Watts setup on the 1st gen.

Yes,the Watts link isnt great,nor are the dissimilar length trailing arms,but there are alternatives.A panhard can be installed to replace the Watts and a 3 link can solve the trailing arm binding issues.Both require much less fabrication than an IRS setup and last time I checked there were PLENTY of *** kicking 1st gen racecars that still use the solid rear axle.
In fact,there seem to be more complaints about the 2nd gen's funky rearend than there are about the 1st gens.Probably because the 1st gen's is simple and quite easy to sort out.
I wont even touch the 3rd gen since there arent many of them out there to get a hold of and play with.Since the 3rd gen is such a well rounded car,I imagine they work well,but the sheer shortage of 3rd gens compared to the other 7's,makes them less "played around with" compared to 1st and 2nd gen parts and swaps.

 

If you think about it, its going to cost a lot to even source a 3rd gen IRS setup to put into your car. Then you have at least a month or more of downtime plus costs of all the materials to make it work. In total, I'd guess the whole setup would cost at least $5000. Then you need the power to actually make this whole thing worthwhile so you spend another $10000 on an engine and tranny to hold the power. Then you have to get the front end up to the same handling level as the rear end, then the brakes need to be done to compensate for the "excessive" power. Then there is wheels and tires to fit the car properly, and to actually fit a wheel and tire package on there wide enough to put the power to the ground your going to need a widebody kit, which is all probably going to total another $5000, if done right.

The point of this is that if you want to even think of doing a "swap" like this, you had better have the rest of the car to go with it otherwise its all for nothing. In the end you could bet on spending just as much as it would cost to buy an FD and slap a single turbo and standalone ECU on it.

 

If money is even a concern, then I would suggest you won't be able to afford to swap an IRS into a first gen.

It's an admirable goal, but being realistic unless you have access to a great deal of knowledge, tools and experience then this will take months and cost a small fortune.

I agree with previous comments - it's about as technically difficult as tube-framing the front of an RX-7.

 

Really, if you want an IRS car for cheap fast and fun, you can find NA FC shells for dirt cheap. I understand you may like the styling of the FB more than the 2nd gen, but if I really wanted a cheap *** beater for weekend canyon battling, Id go with an FC. Especially if I already had the resources to do an REW swap into an FB. Just swap it into the FC and youll be better off as far as handling and power lay-down-ness.

 

All I have to say is:

One step at a time. Start simple and work from there.

 

there was a guy in clemson,sc that swapped a 00' miata IRS rearend into an FB. it took tons of hours and lots of work. i think he was in school for engineering. lats i saw her was trying to sale the car and ive tried to get ahold of him so i could buy it but i think im too late.

 

First off most guys that make power in their FD's swap to the FC's turbo 2 diff!

second the FD motor doesn't make enough power to hurt the GSL or GSL-SE diff so why swap.

third, just cos your swapping the motor doesn't mean the diff needs to be swapped also.

forth, check out what the serious FD guys are doing - http://www.torquecentral.com/showthread.php?t=35499

fifth, if you make power the fc and fd axels are prone to wheel hop because of the poor torque arm design.

sixth, there is nothing wrong with a solid rear axel, it works great!

I have dynoed at 320rwtq and that was with the motor running poorly, i still have the stock GSL-SE diff in my car without problems and i run slicks every weekend.

 

so who runs a ford 9 inch? lol

 

I probably should have, but I decided to work with the stock rear end. There's lots of ways to get great handling out of the stock rear. I havn't tested mine yet since it'll still be a couple months before I'm finished with everything, but it's got to be better than stock. With a welder and a little lathe work you can make a new watts link on the rear of the housing. You'll need a fuel cell since it will hit the stock tank. -

Of course there's easier ways, a panhard bar and a 3 link will greatly improve handling, but a proper watts link is better than a panhard which is why I went this way.

 

that looks very nice