Okay,

So I am currently in the middle of doing a 13BRE swap into my old school rotary, and am looking for some opinions on which rear end I should swap.

For the sake of simplicitiy, you can assume that the swap would be the same as any 81-83 FB.

The engine that is going into the car is currently putting down 417 to the rear wheels, with about 340 foot pounds of Torque. This is at 1 bar. I will be upping the boost eventually, with a expected power output of around 500-525WHP, and close to 400 foot pounds of torque. (I hope )

I will be using the car mainly on the street, but would like to have the ability to put on a set of drag slicks and drop the hammer. Of course, without the fear of breaking anything.

I have looked at many options, from a Jag IRS <-- too expensive, to a reinforced stock rear end. Currently, I am leaning towards a built 8.8 rear end. I know that many have used the 9 inch, but I do not like this option because of the weight, and power transfer issues.

So what all do you think? Will the 8.8 do the trick? any opinons on what else I could possibly use? Any other options that would hold together, at this power level? Or is the 8.8 my best choice?

 

JC,

stock mazda is safe to about 300 and then you start breaking things (semi slicks)
I would go with the 8.8 with a set of heavy duty axles, I think that grannys speed shop has them already modded for 1st gens with a set of moser axles as an option.

kenn

 

Jaguar, or later 1993-1995 RX-7 IRS.

 

Just my opinion on this. Why not use a ford 9". There pretty cheap easy to work with and stong as hell. Plus if you wanted to run different gears for the track than the street you could change them out in about 30min or less. Just a thought.

 

9 inch is very heavy and you wont gain anything over the 8.8 for the power you're stating.

 

Hmm yeah I didnt think about the wieght. what is complete 9" rear end axels and all like 250lbs or something like that.

 

That's why

If I ever thought I could get 500 Foot pounds of torque down, I would consider the weight trade off.

 

The grannys rear is ready to bolt in... Not sure why anyone would want anything different? It woudl cost twice what they are asking to fabricate another rear in.

 

IMHO do it yourself, why use their fitment, from what I understand about the front crossmember its not that great anyway. Use that cash outlay to buy a welder and build the 4 link yourself. I am doing this for my Mazda diff and will post pix, it's really not that difficult, just need some time to take the car off the road, best idea is to work out what you are doing, then get all the parts around and have the rear shortened to suit, then when you're ready go for it all in one weekend.

Note you do have to research or use someone who knbows how to set the diff up and it will need a 4 wheel alignment afterwards.

 

freightliner...18"...this beast will take torque like nothing else...

 

If you gents want to learn more about the Ford 8.8 and 9" rear ends, head over to some of the Ford forums, i.e. Mustangs, and read up. There are differences between the 2 units and pros/cons for each. It is not just the weight difference.

Now go forth and learn, report back. This is a test.

 

Jesuscookies what setup are you runnin with that much HP?what turbo and intercooler and stuff?sorry bout the cross post

 

I don't know if that will work for me. At least not the bolt in part. This is going into an old school rotor, not a first gen. Many of the parts are similar. However, I believe, I will still need to shorten the rear end further for a perfect fit. I will also be adding mini tubs, so more shortening may be necessary.

I would love to swap the JAG IRS in, but I am not made out of money. A custom jag rear end is about 4K.

Based on a couple of sites, I can put together a built 8.8 with strenghtened axles, 4.11 posi rear end, and disc brakes, for about $1200-$1400. That is more in my price range.

 

tell me where can you find this for that price and are the axels original bolt pattern or are you changing the pattern, im looking for one but i dont want to change the bolt pattern since i have brand new panasports not even install in the car yet.

 

If you are wanting a Jag rear end, then use the 3rd gen RX-7