Saab 99 Rally Gearbox ratios re-manufacture

[nutcase]

How does it work on the factory boxes? Same as production version just with no helix?

The factory competition boxes are all helical gearsets, just wider gears, dog engagement, and different ratios.

This would imply possibly not?

http://www.saabworks.com/rallycars/works900/

Not exactly conclusive I know.

[Jordan]

A shame that car was never put to good use. I have a feeling he misspoke or at least doesn't have a SAAB gearset it in... but that wouldn't make sense.

[nutcase]

Possibly/probably not - just knew I'd seen somewhere mention of a straight cut set.

[Crazyswede]

Its possible it has straight cut gears but all the photos I have seen of the 99/900 Saab competition boxes show helical cut. It would be a lot easier to build a straight cut box.

[DrewP]

The factory competition boxes are all helical gearsets, just wider gears, dog engagement, and different ratios.

Forgot, I do remember that now. Brain elsewhere. Mostly thinking about making my own gearsets.

Not good thoughts.

But then I can have a thread like your engine thread! Maybe after the yellow car is running, and I break some gears....

[Jordan]

Photo of S&R gearset:

[Geoff]

http://www.saabworks.com/rallycars/works900/

I took a hell-ride in that car once. (Loved it! )
I remember it being a bit whiney but if it has the factory gearset, then I think it must be helical. It's been years since I rode in the car but I don't remember it having any more of a whine than other rally cars (which have noisy tires).

Straight cut gear sets just require straight cut reverse and reverse idler gears. The problem with the reverse idlers in these boxes (standard or race) is that they're standard shaped gears that have had the outer diameters turned down for clearance. This means you're not getting full contact of the gear teeth.

[Luke]

http://www.saabworks.com/rallycars/works900/

I took a hell-ride in that car once. (Loved it! )
I remember it being a bit whiney but if it has the factory gearset, then I think it must be helical. It's been years since I rode in the car but I don't remember it having any more of a whine than other rally cars (which have noisy tires).

Straight cut gear sets just require straight cut reverse and reverse idler gears. The problem with the reverse idlers in these boxes (standard or race) is that they're standard shaped gears that have had the outer diameters turned down for clearance. This means you're not getting full contact of the gear teeth.

Cool, so the set would have to include a new spur idler and a new spur reverse and we should be ok, for some reason I was imagining trying to maintain the std reverse mainshaft gear and that wasn't working so well in my head. The only trick then would be to make sure the pitches up between the 1st, idler and the reverse work out, but that should be workable.

[nutcase]

Photo of S&R gearset:

Me want :)

Is reverse on these same as standard?

[nkro]

Hallo

900works had a new build S&R helical gearbox here In sweden.

The picture above is early S&R gearset. The late ones have less "dogs" and wider gears and large cluser bearings.

If you change the 1st gear then you have to make everything new for the rewerse.

And only a gearset Is not a rally gearbox !?

Niklas

[Jordan]

Straight cut gear sets just require straight cut reverse and reverse idler gears. The problem with the reverse idlers in these boxes (standard or race) is that they're standard shaped gears that have had the outer diameters turned down for clearance. This means you're not getting full contact of the gear teeth.

Just keep the reverse burnouts to a minimum.

With this gearset you need one of the big ring and pinion sets as well and while you're at it an LSD. Those are somewhat obtainable but add another $3000 to the price tag.

[simo96]

The one we have is the later Big box as Niklas has. Wider gears and larger dogs. It has twin steel selectors, 4 chain sprocket with rally cross sprocket ratios and works gearbox casing with engine drysump, steel rear plate with cooler take off, 3 mount front case and alloy angles welded down the diff casing.
Will had factory assistance with his rallycross car, so I would have thought this box would have come from the factory.

[simo96]

Niklas is on with looking at reproducing these gears as well, so we will wait and see how it all plans out.

The diff we have is a 5.17. As Jonas told me this is really designed for a high reving NA engine and he uses the higher comp diff ratio for the turbo. We will have to make some new 4 chain drives anyway, so we might make one to lift this diff ratio up a bit. Ideally you need to be reving 7500 rpm or above.

[Jordan]

Have any photos of the 'big box' internals?

[simo96]

I will get some off Steve before he whips it across the way to the gearbox place (off-shoot from David Browns Gears).
I can still never work out if big box refers to the wider gear set or the diff ratio?