911

Is the Jap Sti 6 speeder the best box to replace my stock Sti v3 box/diff considering suitable ratios and the 2 litre's capacity to rev to 8K rpm?
My car is a hillclimb competition car, so the ratios/clutch size etc are very important, (pity about the weight!)
I think John Banks knows the answer!
911

T-uk

I would look at dog kits.

the gears of a 6speed may be stronger but the synchro rings will still be battered in competition use.

David_Wallis

As T-uk says.. dog box is the only way to go.

911

Wish you all hadn't said that. A friend may have a Possum borne semi helical box with DCCD coming up for sale. I've driven this dog box and it is FANTASTIC to use. Quiet too! (lots of £££££££££££££££££££££).
Seen my other thread on DCCD into an Stiv3?
911

john banks

All the trouble I have heard of on 6MT is synchros.

David_Wallis

but for hill climbing I think 6spd isnt the best solution.. PERSONALLY!

I think a rally car may be a similar comparison?

Speak to someone that runs a rally car with a dog box.. can point you at someone locally to me if you want?

David

john banks

I'm sure you're right, was agreeing with T-uk for once

David_Wallis

LOL..

911

Why is the 6 speed not suitable? Is it the ratios?
I've fitted an early RA trans (4.11 diffs) instead of my Sti v3 trans to get better performance in a hillclimb. The car is much slower than last year.
If I gun it from the standing start, change to second, to 7000rpm (ish), through to 3rd, there is nothing to deliver, the engine is all out of power, to 4th and it bites agin and pulls strong. Never did that with the Sti ratios.
My interest in the 6 speed is a cost effective solution to the weak 5 speed when the car is in competition and on hillclimb slicks, ouch!
911

john banks

With the RA and six speed gears could you lose time with an extra shift?

Would think the 6MT would be rather slower for changes than a dogbox and not anywhere near like as tough?

The Fixer

Would also expect the synchros to die very quickly with the abuse of hill climbing, rapid full power gearchanges and the traction associated with slicks. Dogbox or dog gear kit for your case would be better suited I think.

911

Hill climbing is a crude form of motorsport (and I used to drag race in the 70's), but I don't thrash (trash?) the box in my Sti.
The real impact is the startline.
To unstick the tyres it is 4500/5000 and dump the clutch. Slipping the clutch kills it dead. So long as you get some wheelspin the shock is 'eased'.
I change gear using the clutch(!) but it is in or out I must admit during the climb.
the Possum Borne semi-helical dog box i have tried on a sprint track is stunning but you do have to change fast. All the time, so very tiring in traffic driving to and from the hillclimbs as I do.
I seriously doubt that the synchos will die, but will the ratio's work for me?
The RA box i currently have in the car seems to give me no benefit compared to the Sti box(which is pretty short anyway)
I drive the car 3000 miles a year, not sure the dog box is the way to go(?)
911

David_Wallis

Thats only 8 miles per day.

911

Not a daily driver John.
The furthest hillclimb from me is only 50 miles one way, and a hill climb is about 12 gearchanges long at the most, so i know what you are saying!
I shouldn't worry should I?
I love hard sharp cars modified just a bit too far for the road, you should 'experience' my old 911 in hill climb trim, crude? You bet.

I just don't want to spend the money!

Bloody cars.
911

Mark A

iTrader: (1)

And the extra weight of the six speed slowing you down

How many more kilos does one weigh over a five speed John

Mark A

john banks

20kg

911

Add 20 kg, spend £1500 on the 6 speeder. The Dog box will cost about £4000 all done, spend the £2500 on a new turbo, injectors and Gems (just) and that 20 kg will be history.
The weight is in the middle of the car almost too, so that's a bonus.
Yes I know, the Possum box makes more sense.
911

Mark A

iTrader: (1)

Keep searching the Jap salvage yards or try the US for new box.

Mark A

carlos_hiraoka

Many of the STi ver 7/8 group N WRX rally cars are using the 6MT gearbox with no problems. It is a very close ratio gearbox and will always keep your car on the "right spot" although you will find yourself changing gears more often. Remember that the JDM 6MT unit already is close ratio with the 3.9 final drive (STi's and STi RA's all come with the 3.9 final drive), I would say to go for the 6MT .....

Carlos H.

911

Thanks again everyone.
with my strange AP clutch problem and the RA box not cutting it on the race track, I've deceided to strip the lot out, re fit the Stiv3 box/diff and a fresh whatever clutch to gat the car back to being driveable at 10/10ths.
That will do for the rest of the season if the slicks don't snap the box. If that happens I'll bring the venerable hill climb 911 out to play.....solid simple car, just too slow!

I think a 6 speeder for the Xmas rebuild will prepare the car for the turbo/injector/Gems bit then.

The more economic way is to buy Carman's Sti RA for £13K or so as it has all been done!
911

CustomScoobyIOM

911- YHPM mate!

T-uk

I would say dog kit would be best but if you think the synchros can take it , the JDM 6speed could be a nice priced option.

I think the short gearing is only really an issue with big torque , especially when combined with a low rev limit.