s2 gearbox on turbo?

[nicksonmsport]

i have an s2 breaking, is it worth keeping the s2 box to fit onto turbo track car for shorter ratios keeping the turbo on song? will the ratios suit, and are the gearboxes strong enough to cope with 300+hp

any issues in swapping the boxes or is it a straight swap

thanks
nick

 

[chrisg]

Nick

I don't have the exact figures to hand regarding torque, ratios etc. However, my first instinct would be to say no for two reasons:

1. The 250 Turbo gearbox had strengthened/hardened 1st & 2nd gears and heavy duty bearings to cope with the extra torque, the S2 box (particularly a worn one...) probably won't cope.

2. Porsche were and are very clever with their engineering - I suspect the ratios won't work.

I believe that mechanically it will fit, ISTR that the torque tube for the S2 and Turbo are identical and certainly the match up with the gearbox is. With 924's there were a number of different boxes with very different outputs and different TT's.

Hope this helps and I'm happy to be corrected on any of the above points by those more knowledgable than I !

 

[Neil Haughey]

ISTR its popular in the states to use the ring and pinion from an S2 in the turbo box to gear it down for track use. Loads of evidence of it making a much faster car but it will top out at something like 145 or so. Not a problem really as one of the guys racing a GT3 at Silverstone told me that was the sort of speed he was getting up to on the Hanger straight so I think its unlikely one will rev it out on UK tracks without some mad Bhp.

 

[944 man]

Youll need an oil cooler on a hard working transaxle too. With regards to the top end that you lose fitting an S2 CW&P - the cars are bloody frightening at 150mph (or 130 knotts, as it should be known! []), so not being able to exceed that isnt much of a penalty.


Simon

 

[nicksonmsport]

ok thanks, good info, will keep this gearbox in case i want to swap the final drive over. gearbox needs an lsd anyway so can swap the ring gear over at the same time. im sure 150mph is plenty !

 

[Neil Haughey]

ISTR reading somewhere a generic rule for race/track cars is that anything over 250 Bhp should have external oil cooling so Simon is right to point this out. Porsche considered it important enough to fit one as part of the M030(?) package.

 

[nicksonmsport]

yes of course external oil cooler will be on the list of to do. is this something that can be retrofitted easily.

 

[Diver944]

ORIGINAL: nicksonmsport

are the gearboxes strong enough to cope with 300+hp

Plenty of cars on the forum have been above or around the 350bhp mark for a number of years without any issues. It's apparently the torque that can wear them out quicker once you're over 450lbft. A 2.5L car will struggle to hit that figure that so it's only the 2.8L, 3.0L and above cars that really need to keep an eye on things. I did 10,000 road miles at 480lbft without any gearbox problems, but it was only a couple of trackdays

I think you'll find that once you get over 300bhp the gear ratios suddenly seem to get a lot shorter anyway [8D]

 

[os951]

S2 box under Turbo i s one of the best modifications you can make. You just need to have "right" version of it. I searched special Switzerland only box two years. This box is basically same as Turbo AOR. When the right box was found, there were two available from a same seller in Switzerland. I bought both of them.
If you cannot find a S2 box, get a S box. S box is basically the same as the early Turbo box, but with shorter gears.

 

[333pg333]

If nothing else keep the ring and pinion and put it in a OEM 5 speed. This is one of the best mods for a track car you can do. I can speak from experience.