A + gearbox with x pin diff
Turbo Mini Forums

Hi Guys,
Can anyone tell how much power or torque the standard A+ gearbox can handle, before I have to swap over to straight cuts.

Edited by Nick on 24th Dec, 2015.

I would say 150-160bhp as long as fitted with a x pin. I'm sure people have ran more though.

Class C 3rd Place Avon 2011 14.18 @101mph

that sounds about where they start shitting themselves to me, although it can be very variable, depending on engine spec, really its the torque that kills them, or shock loads

We borked the first motion bearing on the van's helical gearbox with 140nana and 140ft.lbs using straight cut drops.

It was driven enthusiastically though, I think we had about 20 slips from Showdown that year! lol

Edited by John on 23rd Dec, 2015.

If something is worth doing, it's worth doing half of.

Cheers Guys, just thought I would check to be on the safe side, the engine spec for the first stage, shouldn't be making over 110bhp, so I think I might be safe for now.

if you are running a standard helical gearset and placing that through it on helical drops it wont survive long it will take 4th gear out and the 4 gear on the head set. do as john did run SC drops and it will survive, better still spend your money on a minispares clubman gearset with better ratios and run standard helical drops that combination will survive well over 200 hp as proven and you dont get the SC drop whine..............hope this helps

You mean third gear Steve..... there is no fourth 'gear'. Fourth 'gear' is exactly the same as the clubman set, or are you saying the clubman set is shit too?

As Joe said, its the torque that does the damage. I know KAD have built helical gearboxes forr some of their customers for some of their 160hp road engines, obviously lesss torque than a turbo engine, but still significant.

I built one very much similar ensuring every tolerance was at bottom limit. Thats not easy to do as the parts required to set 1st, 2nd and 3rd gears thrust clearances on the main shaft are not available. It takes careful selection of parts from 3 or 4 gearboxes, and may need careful machining of some parts to get it all just right. Swiftune lay shaft, KAD pinion support housing, and the turbo input gear support bearing to complete the package.

The biggest problem with a standard helical gear kit is more that 1st gear is far too short with big torque, almost useless, in my opinion.

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Ok cheers guys for the advice, will look at getting a set of SC drop gears fitted onto the box.