Mazda Rotary Club

Anyone know where I could go to get a drag racing driveline like T56 gearbox + cobra 8.8 installed in an FD in the UK? I have a 20B turbo setup but the RX-8 gearbox and factory rear end with Kaaz LSD isn't going to cut it on the strip.

Hello Tom.

I will mail some I know in America tonight as I have  a feeling that the bell housing is available to fit this box to a Rotary.

One thing though, have you looked at ratios as I'm sure someone said  to me that the ratio's are junk for a rotary, i.e. too far apart ?
(Not enough V8 type  torque to drag it through the gears)

Not sure what ET's your going after but it may be worth knowing, if you didn't already know, James Willday got into the 8's with a 700+ BHP 13B using just an FD box and a Kazz  diff.

Please Keep us informed anyway about the build, as many here would love to see your build.



           

Do you mean stiff 8.8 rear axle? Cause dropping rear end with links to a car just wont do anygood. Just bolting it on without knowing what you are doing, makes car launch worse than with stock IRS...

You have to figure out do you want to use 3 or 4 link. Use Panhard or Wat. And what kind of links you want, raising or dropping links. Have to figure out center of mass in cars chassis, so you can calculate links lenghts...

Unfortunately my english isnt so good, and this thing is difficult for me to explain...

Only way to do stiff rear axle swap for drag racing is to contact car builder/racer who can do all those things for you. Chassis setup and getting these things to work is witch craft, and needs pro to do it...

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James used a hks gear box

Best bet is to search online for the kits, I think you will be looking around 3500 for the gear box alone.

As for the diff I can't remember if you replace the whole rear subframe or just part of it.

I will have a look see what I can find as iv looked for this before

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https://www.grannasracing.com/products/fd3s-mazda-rx7-ford-8-8-rear-end-swap-kit-by-ronin-speedworks

Have you already got the diff and gear box or are you wanting to purchase one and get it fitted?

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Here's the gear box for you

https://www.grannasracing.com/products/mazda-rx7-t56-magnum-swap-kit-13b-20b-fd3s

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Hi all, thanks for replies.

I'm surprised to hear that about stock diff. I broke mine on the start line of a hill climb (not especially good traction) earlier this year, and just to get going again, replaced with same 3.9 and added Kaaz LSD. Rather than risk blowing this up at the strip I thought I should do something more proactive. Definitely open to alternatives.

I believe there are IRS versions of Cobra diff but I don't know much about them. Just asking around people running street drag FDs in the US.

I'm mainly looking for workshops with experience so I can discuss it with them.

Do you know what kind of horsepower and torque you are making?

I know James's drag car had issues with breaking the gear box and maybe the diff but it ended up being an alignment issue from what I can remember. Once they figured that out he was launching hard on street slicks and ran an 8.82 @160 ish

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It's roughly 644hp at flywheel (measured on a chassis dyno with drivetrain correction). Not sure about torque.

I did have significant wheel hop on that start line. Perhaps that was the issue.

160mph is way above what I'm expecting so this is good to know. What about the RX-8 6 speed though?

Have you changed all of the bushings and mounted a diff brace?

Wheel hop will definately caused it to break.

You will be producing more torqu with the 20B but James and other drag cars have made more power than you for sure

As for the gear box... The input shaft and the syncros are the problem, hard launching often snaps the input shaft especially if there's a lot of twist and flex on bushings and suspension etc.

There are gear box braces available but they can make it noisy in the car from what iv been told by lads that used them

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So I have one of these (not fitted) https://www.ebay.co.uk/itm/290967101425

Workshop that fitted new diff and LSD advised this diff brace seemed to be wrong item for my car and too flimsy to help anyway (?).

Sounds like it'd be worth getting these addressed properly (bushings) and various braces and then see how I go.

There is also a KG parts diff brace avaliable too.

I used to have the KG one on my fd, it was very heavy but helped

Bushings definately a priority. Suspension bushings and also the diff bushin, that's a right ball ache as you have to remove everything

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Tom, allegedly some UK drag cars were using RX-8 6 speed boxes, but on circuit I went through 4 of these with at the time less than 500 brake.

RX-8 5 speed boxes are super cheap and basically the box is a modern day FD box with even the same ratios with only top being a little longer.
Just got almost three seasons out of an RX-8 5 speed box.   

I also used theKG parts Diff brace up the strip and it stopped the diff leaping up and down.

The brace you ordered is just to combat the engine twist and the chance of missing a gear 

Thanks Clive and Grant. Super helpful.

Any ideas where I can get some of these things worked on? I live in London and have been taking the car out to a workshop in Oxfordshire. Experience there has been good but a workshop closer to home would be good.

I think power gains are in Romford? They helped James with his car run the 8.82 1/4 mile

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As those gents said, FD gearbox and diff are actually quite strong. But mountings usually cause them to fail.

Torque that your 20B makes, will probably blow up that T56 too, so I reckon that best optio for you is to use those cheap 5 speed Renny boxes. However, you will have to change clutch type.

FD diff can take lots of beating. That wheelhop tels that your bushings are gone basically. So change all of them. Get diff brace/cradle (dunno correct word for it), and pinion snubbers. Also, gearbox and PPF should be bolted together proberly. Any movement can make them fail, especially PPF.

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Btw, James is super good dude, I reckon if you contact him, he will help you out.

As for his (old) car, that car took lots of beating thru several years, and still he went milk shopping with that car

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