Running around 275lbft of torque in my race car with the Rotrex C38/91 I've had my fair share of gearbox failures. I've had 4 or 5 fail and that includes Cryo'd boxes too; the initial failure has always been 3rd gear, closely followed by the others as I continue to race with a ever-decreasing ratios.
The standard gears are very hard but have a very low ductile strength meaning that they break due to shock-loading as apposed to wear.
I've been speaking to a very well known and respected gear/gearbox manufacturer and they have investigated the best options available and the cost thereof.

We propose to make dog-engagement 3rd and 4th gears to fit the standard gearbox to achieve:
1. A very high strength gearbox
2. As low cost as possible
3. Retro-fit to standard gearbox
4. Able to salvage a gearbox that only has a broken 3rd and/or 4th gears
5. Standard ratios (which have proved to be perfect for my car)
6. Retains synchro for 1st, 2nd, 5th and 6th
7. Keeps transmission noise to a minimum
8. Perfect for road, track, rally and race or a combination of uses
9. A full build service can be organised, price to be advised and donor gearbox required
10. A drive-in, drive out service can be organised, price to be advised and this would not be same day service

Parts to be Manufactured:
Dog Ring
3rd Gear
4th Gear
3rd/4th Layshaft
To be made from extremely durable S156
Heat Treated, Hard-Turned and Internally Ground for absolute precision

Cost:
£895
A cheaper option using EN36 will also be available at a cost of £750, but I will certainly be choosing S156 myself.

Timescale:
I need definite orders and a deposit of £150 by the end of September
Remainder of payment must be paid by the end of November
The gears should be available by the end of November although I'll say definitely before Christmas.

Group Buy:
As a one-off this kit would cost around £1,500 so to make it possible I have to place an order for 10 kits. Please add your name to this list only if you are a definite and are committed to pay the deposit and full payment on time. Please indicate S156 £895 or EN36 £750 on the list below:

1. ash S156 £895
2.
3.
4.
5.
6.
7.
8.
9.
10.

Is the En36 going to recieve any sort of case hardening treatment as although its a good mild steel, its still soft. However, if your looking for the cheaper option to not have h/t on the shaft, maybe plump for En24T instead.

Unless ive read that wrong. Seems a good price though.

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See the sheer power and might of the lesser known burrowing owl.

EN36 is very good if case hardened. It withstands shock pretty well and whilst being nice and hard too.
I only suggested 24T if no HT was going to happen as 24T is already quite hard and tough. They would have steered you away from the basic EN24 as thats through hardening and wouldnt withstand the battering too well.

Plus having read that back, I was only reffering to the shafts not the gears. Obviously the gears need to be hardened.

Anyway, sounds a great idea and best of luck with the group buy.

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See the sheer power and might of the lesser known burrowing owl.

Absolutely... as long as you don't try it with any other gears!

No more interest for this kit? I'm really surprised. If you are interested please register your interest in the next week or you will miss out.
Need a minimum of 6 orders for this to go ahead at all:
1. ash S156 £895
2. Ross S156 £895
3.
4.
5.
6.

bump!

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Super high boost Completed, destroyer of gearboxes and 160mph club

I'm not aware of any kit available that quotes a high enough torque capability of a charged 306. I also don't want to change the ratios or lose 6th gear!

Im a little surprised more of the HB guys are not interested either. If i was heading down that route then i would certainly be considering these just for the piece of mind and reliability

You never know, one day i may go crazy and get some high boost action going on

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Just Drive It

house build = i am broke

simple answer

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TEAM HIGH BOOST SUPERCHARGED RALLYE

My Rallye project thread

Wish I could afford this, if only it was a couple of months later as I've hopefully got a new job lined up

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Team 'unintentional rat look'

To be honest Ash, most of the guys aren't on here any more. I would be doing this if the high boost I had been offered had come to fruition.

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Nothing to see here

Let me know if you would like to join the order because I'm planning to place the order tomorrow.
There's no way of knowing what the next weakest link is, although there is no indication that the shaft can fail and the boxes are quite rigid; a twisting gearbox would promote failures.

good man as you say to rare a chance to pass on it.

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Super high boost Completed, destroyer of gearboxes and 160mph club