Clive's 400 BHP Super GT RX-8 Race Car

[Grant Monkhouse]

Something I learnt off Kev ages ago and through looking on the rx7club forum about strengthening the gear box by insert a steel plate under the access panel on the gear box. Iv got a 1/4 mild steel plate on the gear box I have, it is also over sized so I could use it as extra mounting points too bolt the gear boxin more places too the chassis, it’s extra added weight but not even 10kg at worst, being a race car I wasn’t worried about any noise transference into the car.

FD gear boxes are rather expensive now because of the redonkulous FD prices. The rx8s are cheaper and clive wouldn’t need to get his drive shaft length changed as and rx8 gear box is shorter than an FD gear box?

A lot of people talk about using the turbo 2 gear box but the way I see it is that is older than an FD gear box so most likely been abused more maybe?

I don’t think clive could change too an FD gear box as he would have too change the clutch type from pull too a push type? Rx8s clutch is the opposite too and FD isn’t it?

I remember a guy on rx7club making a prototype gearbox sumo brace/strengthener for FD gear boxes, iirc he made it about 3/4-1” thick which added a huge amount of volume inside the gear box too hold more gear box oil, don’t know if that would benefit a gear box at all but I suppose you can’t go wrong with too much lube can you??


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[re japi]

Well, I would choose 8s 5speed too. Its basically the same that FD has. And lots cheaper. So no point choosing FDs or T2 box...

Also, my opinion is that 8s 5speed, compared to those other 5speeds, has best 1 and 2 gear rations for racing...

What I have seen and heard, 6 speeds main axle is weak because "that extra gear". Dunno how to explain it in english...

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[Grant Monkhouse]

https://www.rx7club.com/group-buy-product-dev-fd-rx-7-269/bubble-tech-transmission-spacer-1070094/

Found it


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[Grant Monkhouse]

Found this also

https://www.rhdjapan.com/attain-extra-large-transmission-oil-pan-fd3s-fc3s.html


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[Grant Monkhouse]

I would personally just buy piece of steel roughly the right size for cheaper from your local metal stock shop or eBay and cut it and drill out yourself. Took me an hour or so to make mine up, think I used a grinder to cut most of it out then a jigsaw to neaten bits up. I drill the holes for the bolts over sized just to make it easier to fit.

Longer screws are only a few quidz


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[clive]

Rx8 5 Speed now installed 

RX-8 5 speed:
1st: 3.483
2nd: 2.015
3rd: 1.391
4th: 1.000
5th: 0.806

RX7 FD
1st: 3.483
2nd: 2.015
3rd: 1.391
4th: 1.000
5th: 0.719

As you will see above the RX-8 Box has a higher ratio 5th giving a bigger gap between 4th and 5th but hopefully this wont be too much of an issue on track

Apparently the FD box fits when using the RX-8 5 bell housing which is a straight swap, one problem is the gear leaver sits further back, the power plant frame has to be chopped about plus a new prop has to be made, my old mate Glenn wants his FD close ratio box fitted in his recently bought track day RX-8 so we had already started looking at this.

Another plus side to swapping out the six speed is that I now have a lighter box in the car     

[re japi]

Rx8 5 Speed now installed 

RX-8 5 speed:
1st: 3.483
2nd: 2.015
3rd: 1.391
4th: 1.000
5th: 0.806

RX7 FD
1st: 3.483
2nd: 2.015
3rd: 1.391
4th: 1.000
5th: 0.719

As you will see above the RX-8 Box has a higher ratio 5th giving a bigger gap between 4th and 5th but hopefully this wont be too much of an issue on track

Apparently the FD box fits when using the RX-8 5 bell housing which is a straight swap, one problem is the gear leaver sits further back, the power plant frame has to be chopped about plus a new prop has to be made, my old mate Glenn wants his FD close ratio box fitted in his recently bought track day RX-8 so we had already started looking at this.

Another plus side to swapping out the six speed is that I now have a lighter box in the car     

With that 5 gear ration, I dont think you have a problem, you have so much grunt...

Umm, do you need 8s starter also? I remembered that they have some differences. Or spacer... I think we talked with Aston about that, when we investigated options for bros car...

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[re japi]

Also, other problem is that PPF. Im not sure what needs to be done if you want to some how use it, original cant be used that for sure I reckon. But how about custom made, like bros car has...?

I was goint to suggest that steel plate, but saw that Grant already suggested that. Its really good and cheap option. Also, another option is to make steel bands around box that holds gearbox warping. My friend used those in Volvo gearboxes, not pretty but they work...

A bit of topic but I think that one Finnish company now makes straight cut teeth dogboxes for FD now...

[Grant Monkhouse]

With regards too the ppf, I know of one person that we don’t mention on here any more built an FD many years ago, a wide body camouflage paint track car,
That didn’t bother using a ppf as they tied the gear box and the diff into the roll cage of the car and the chassis of the car. This FD was said to be around 950kg

Obviously it’s a lot of work to do but just saying it can be done.

Is the ppf essentially there too tie the driveline together? From
Front too rear.

So wouldthere be a lot of flex allowed from the engine all the way too the rear wheels?

I did a little bit of searching last night night and a common problem with FD gear boxes, so I would guess this applies too rx8 boxes, is third gear, whether it is causing broken shafts, synchros are even the gear itself. Mostly linked too the twisting/flex. So I would see it as the engine is starting to make a lot of load and then shifting from 2 to 3 at 8,000? Causes the damage?

With the gearing in third getting closer too 1-1 there’s a lot of “torque” ( yes torque on a rotary ) being loaded through that box isn’t there. Lots of twisting with all the drive line.

Stop the twisting and send the load through the chassis OR too the next weak link which is either the drive shafts or the diff


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[re japi]

Yes, we have been thinking that too, bolting rear and engine straight into chassis basically. But its going to be massive job I reckon

Well, I dont think PPF is crusial, but it really helps putting all the power into tyres. Mazda used lots of time and effort to it, so I quess it really matters somehow. Just because it thights those components together, not allowing them to flex, it helps. Afterall, many FDs have broken PPF so it kind of works

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[boosted]

When you had a piccy of your fd box up Grant i wondered what that plate was for....
Good turn around Clive!!!

[clive]

Jarno, hope your right about the ratio and grunt 

Yes you need an RX-8 starter with an RX-8 box as it sits 10mm further in than an FD starter. 

[boosted]

Is it worth tearing the blown box Clive for abit of root cause analysis....or in laymans speak...."what broke inside"...
Like Grant says maybe some simple bracing...but hey its your power....the Westy with std power and 560kg...box is the original had plenty of abuse...synchros are showing wear...but its held up fine so far...

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[exiled-viking]

some nice info here good Sunday morning reading 

[Grant Monkhouse]

When you had a piccy of your fd box up Grant i wondered what that plate was for....
Good turn around Clive!!!

Yeh it looks weird why I had it on there butmakes a lot of sense when I explain it doesn’t it


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