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Author: Subject: Gearbox Choices - RX8?
Double R

posted on 10/11/20 at 09:20 AM Reply With Quote
Gearbox Choices - RX8?

Morning fellas,

It's been a while since my last post, and I've got the GTS covered up with a few plans for the winter.

I wanted to check what gearbox you're all running?

I originally had a T9 rally-spec straight cut box, but changed it last year to a standard T9 as the noise was noticeable for road use.

Now I've been on a few track days this year at Croft, Donnington and Cadwell, and whilst the handling and engine upgrades work well, the gearbox is becoming a problem.

The shift is clunky, and the downshift is slow, with the ratios being pretty clumsy on track.

So I was debating two potential routes:
1. Get the box rebuilt with better internals and close ratios - circa 1600
2. Replace the T9 with the 6 speed Mazda RX8 box, with adaptor plate, custom chassis mount and propshaft

Question is, has anyone done this, as I'm thinking fitment will be a close call?

Thanks!
RR

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big_wasa

posted on 10/11/20 at 10:54 AM Reply With Quote
You don't say what engine ?
Better than the Rx8 box is the Mx5 N7 box. Retroford do a conversion for the zetec. The conversion is nicer and more refined than the rx8 adapter. The box is smaller and lighter than the Rx8.

I will have to find a way of uploading some photos. I have all the bits to upgrade my mt75. A great box but has crap ratios.

[Edited on 10/11/20 by big_wasa]

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AntonUK

posted on 10/11/20 at 11:05 AM Reply With Quote
I put a rx8 box on my 1.8 zetec last year... massive improvement to the feel of the box and 6th gear is a bonus too.

There was a guy on facebook selling kits that included the plate and a different arm to allow use of a cable clutch.





Build Photos Here

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CosKev3

posted on 10/11/20 at 11:45 AM Reply With Quote
I run a 6 speed in my car,great box but much bigger than a Type9.

My chassis was a Type9 sized chassis, I cut and smoothed loads of parts off the Rx8 box that I didn't need to use and still had to modify the tunnel in my chassis to get it in.

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CosKev3

posted on 10/11/20 at 11:47 AM Reply With Quote
You will probably need to change your diff too if you want all 6 gears to be useable as first gear is very low.
I was running a 3.38 diff and first gear was a waste of time,now I'm running a 3.14 and all 6 gears are useable,although first doesn't get you down the road very far,I am running circa 250bhp though.
Sixth gear now is lovely for cruising.

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Double R

posted on 10/11/20 at 12:04 PM Reply With Quote
quote:
Originally posted by big_wasa
You don't say what engine ?
Better than the Rx8 box is the Mx5 N7 box. Retroford do a conversion for the zetec. The conversion is nicer and more refined than the rx8 adapter. The box is smaller and lighter than the Rx8.

I will have to find a way of uploading some photos. I have all the bits to upgrade my mt75. A great box but has crap ratios.

[Edited on 10/11/20 by big_wasa]


Aha apols, running a 2.0ltr ST170 Zetec, with ARP bolts, gasflowed head, Piper 285 cams, VVT delete, on Jenvey 45's and an emerald ECU. Probably an optimistic 200-210bhp.

Also the GTS is the wider version, so I'm thinking if I cut down the box with the adapter plate and new mount, it would fit?

Thanks!
RR

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Ugg10

posted on 10/11/20 at 02:23 PM Reply With Quote
The ratios on the RX8 box from 2-6 are almost identical to a quaife clubman so you could just use ratios 2-6 and leave first for really steep hill starts but with a stock 3.62 or 3.54/3.77/3.89 6th is still not a cruising gear but acceptable.

RX8

1st - 3.760
2nd - 2.269
3rd - 1.645
4th - 1.187
5th - 1.000
6th - 0.843

Quaife Clubman

1st 2nd 3rd 4th 5th
2.040 1.540 1.210 1.000 0.870
2.200 1.690 0.930
2.390

Benefits of the RX8 are that is it built for 250hp and 250ftlb (Nissan Sylvia s15 2.0l turbo) and can rev to 9k (rx8/s2000), is helical not straight cut and if it goes bang then it is 200ish to replace not 2k. Worth noting the RX8 box is an OEM version of the Aisin AZ6 which is found in a number of cars just with different bell housing elements (still integral though).

https://en.wikipedia.org/wiki/List_of_Aisin_transmissions#Longitudinal_rear-wheel_drive

Quick side by side comparison.



On the back end of a Zetec SE Puma engine





[Edited on 10/11/20 by Ugg10]





---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com

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Double R

posted on 10/11/20 at 03:25 PM Reply With Quote
quote:
Originally posted by CosKev3
I run a 6 speed in my car,great box but much bigger than a Type9.

My chassis was a Type9 sized chassis, I cut and smoothed loads of parts off the Rx8 box that I didn't need to use and still had to modify the tunnel in my chassis to get it in.


Hi there, thanks for the advice

I've just measured the tunnel again, it looks like it's going fowl around the gearstick end, as the wider end goes from 11.5" -9" to 8" then to 6" at the lever.

How much modifying of the tunnel did you do (roughly)

Thanks!!
RR

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Oddified

posted on 10/11/20 at 04:07 PM Reply With Quote
If you were to stay with the type 9, i'd very strongly recommend the SPC semi helical gear kit, absolutely superb. Smooth, quiet, excellent ratio's and strong.

Of course as mentioned, the price of an RX8 box would make that route very tempting though!.

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CosKev3

posted on 10/11/20 at 06:52 PM Reply With Quote
quote:
Originally posted by Double R
quote:
Originally posted by CosKev3
I run a 6 speed in my car,great box but much bigger than a Type9.

My chassis was a Type9 sized chassis, I cut and smoothed loads of parts off the Rx8 box that I didn't need to use and still had to modify the tunnel in my chassis to get it in.


Hi there, thanks for the advice

I've just measured the tunnel again, it looks like it's going fowl around the gearstick end, as the wider end goes from 11.5" -9" to 8" then to 6" at the lever.

How much modifying of the tunnel did you do (roughly)

Thanks!!
RR


There is quite a lot of material you can remove off the RX8 box tbf!

I had to modify the upright on the chassis drivers side,and remove a diagonal bar.

Also had to cut out part of the bell housing to get that in the tunnel.

If you look at the RX8 box it's very fat about half way along compared to the Type9 box,that's where I struggled for clearance.

If I could have mounted the engine and box on a angle, not that I wanted too as imo it looks awful,I probably could have got the box in ok.
But with my V6 I didn't have the room at the front of the engine to the top chassis rails to be able to mount it on a angle.

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Ugg10

posted on 10/11/20 at 07:53 PM Reply With Quote
If you are using a mechanical speedo or an electronic encoder on the type 9 then you will need to sort this as the RX8 box has no tachometer/Speedo output mechanical or electrical. Probably need to put magnets on the wheel hub or prop shaft.





---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com

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lsdweb

posted on 10/11/20 at 08:19 PM Reply With Quote
quote:
Originally posted by CosKev3
There is quite a lot of material you can remove off the RX8 box tbf!


Any photos of what you've trimmed off? Ta.

Wyn

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Double R

posted on 10/11/20 at 10:05 PM Reply With Quote
quote:
Originally posted by Ugg10
If you are using a mechanical speedo or an electronic encoder on the type 9 then you will need to sort this as the RX8 box has no tachometer/Speedo output mechanical or electrical. Probably need to put magnets on the wheel hub or prop shaft.


Yes I was thinking about that, I have magnets on the prop so I'll probably go down that route again.

I'm really tempted by the idea of just sending the T9 box off to be upgraded but it's a lot of spend, particularly when you look at the cost of the Mazda one.

I guess the other point is, if we know the RX8 box will go in with some modification, then I'm like the idea of the challenge, especially when there's not a lot going on at the moment.

I'll get in up in the air over the weekend have another look.

Kev - did you re-weld the chassis legs back in afterward?

Thanks!
RR

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CosKev3

posted on 11/11/20 at 06:56 AM Reply With Quote
quote:
Originally posted by Double R
quote:
Originally posted by Ugg10
If you are using a mechanical speedo or an electronic encoder on the type 9 then you will need to sort this as the RX8 box has no tachometer/Speedo output mechanical or electrical. Probably need to put magnets on the wheel hub or prop shaft.


Yes I was thinking about that, I have magnets on the prop so I'll probably go down that route again.

I'm really tempted by the idea of just sending the T9 box off to be upgraded but it's a lot of spend, particularly when you look at the cost of the Mazda one.

I guess the other point is, if we know the RX8 box will go in with some modification, then I'm like the idea of the challenge, especially when there's not a lot going on at the moment.

I'll get in up in the air over the weekend have another look.

Kev - did you re-weld the chassis legs back in afterward?

Thanks!
RR


Yeah welded in new uprights in positions to clear the gearbox,and welded in a extra one which runs across from one side of the tunnel to the other below the bell housing for peace of mind!

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CosKev3

posted on 11/11/20 at 06:58 AM Reply With Quote
quote:
Originally posted by lsdweb
quote:
Originally posted by CosKev3
There is quite a lot of material you can remove off the RX8 box tbf!


Any photos of what you've trimmed off? Ta.

Wyn


Hi

I can't upload pics off my phone to this coal fired forum

Email me @teare820@btinternet.com and I'll send over what I've got.

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