Strongest Gearbox Possible

[Geoff]

Its a fantasy price. "lilla lådan" Rally gearbox. LSD, Gearset 6.31. Strongest gear house.
Steel lsd cover. etc.

But the seller Is StigBolmqvist Motorsport AB.

I thought the price seemed kind of high to me too. Maybe Stig doesn't really want to sell?
Didn't he try to compete or drive a 99 turbo rally car recently (maybe at Nurburgring?) and the gearbox broke right away? hmmm....

[Geoff]

What do you think ?

If you have the time and money!

[Hans]

Its a fantasy price. "lilla lådan" Rally gearbox. LSD, Gearset 6.31. Strongest gear house.
Steel lsd cover. etc.

But the seller Is StigBolmqvist Motorsport AB.

I thought the price seemed kind of high to me too. Maybe Stig doesn't really want to sell?
Didn't he try to compete or drive a 99 turbo rally car recently (maybe at Nurburgring?) and the gearbox broke right away? hmmm....

It was a German-prepped c900.

Germans can't do anything right. (Note my name before flaming...)

[Luke]

Its a fantasy price. "lilla lådan" Rally gearbox. LSD, Gearset 6.31. Strongest gear house.
Steel lsd cover. etc.

But the seller Is StigBolmqvist Motorsport AB.

I thought the price seemed kind of high to me too. Maybe Stig doesn't really want to sell?
Didn't he try to compete or drive a 99 turbo rally car recently (maybe at Nurburgring?) and the gearbox broke right away? hmmm....

It was a German-prepped c900.

Germans can't do anything right. (Note my name before flaming...)

And it was actually Per Eklund, not Stig

[airsweden]

Like riding shotgun with Per! He gets passed a bit but It never hurts my feelings when I get dropped by a well prepped and piloted 911 or E30. Its the back end of a Volvo I can't stand to see. Right about 2:40 he is able to wring some unholy speed out of that thing. Too bad there's no display for the rev counter and mph.

http://www.youtube.com/watch?v=Kk_KnfF_mh4&feature=related>

[mmoe]

For what its worth to those who are interested, I gathered some rough estimates for production of a small run of cast iron transmission cases. Locally (Seattle) and from qualified shops it would run in the neighborhood of $2500-$3000 each to produce a run of around 10 cases given that the cases are of similar design/complexity to the original Saab transmission. That does not include the primary case, which would be roughly the same to produce in addition to the main case. So, you'd have to figure on around $5000-$6000 just to get a complete case produced in limited quantity. I should say that these were not the cheapest shops, but some of the best shops for casting and CNC machining. The CNC machining company produces it's own racing components for hydroplanes, so their qualifications for this kind of work are likely to be unmatched by many shops. The machining estimate was contingent on supplying Solidworks or similar solid model files of the part(s) and the addition of a large fixturing block cast onto the parts for clamping in the machining center (to be milled off at the end).

The plus side is that you could modify the original design considerably but keep it within the constraints necessary to maintain the factory engine/transmission installation configuration. By the time you got some gears in there, you'd probably be well over $10,000 though, so I guess for many of us it may be a case of diminishing returns since a knowledgeable home mechanic can easily rebuild these transmissions between 10 and 40 times over for that price. Would a $10,000 custom transmission outlast a reinforced stock Saab transmission by that kind of factor? If you were racing and could justify this expense, I'd say it would be worthwhile. For the rest of us who just like to hit the gas on the freeway or go to local tracks every now and again it may be a hard pill to swallow.

[Crazyswede]

not to mention the uprated suspension for the additional mass of a cast iron case I think it would be cheaper to have one milled out of a solid chunk of Aluminium on a 5 axis mill.

That said, if there is enough interest we could have a set of spur gears made up to go in a stock case and I think most people would be fine.

[thereisnospork]

For that kind of money it seems like surface coatings such as WPC or nitriding would be the better bang for your buck in terms of improving gearbox longevity.

If you really wanted a cast iron case though, it could probably be done on a budget ($500-750ish) using a lost wax casting w/ thermite as your iron source in a big backyard. However I'm no metallurgist so I dunno how strong/fault free the resulting part would be. It would certainly be heavy though...

[SwedeSport]

What about making a case from billet aluminum on a 5 axis mill? It would be costly, but lighter than cast iron, and much stronger than stock if you add structure, and material in right places.

[Crazyswede]

What about making a case from billet aluminum on a 5 axis mill? It would be costly, but lighter than cast iron, and much stronger than stock if you add structure, and material in right places.

echo?

[Geoff]

Hey guys, has anyone thought about milling a case out of aluminum on a 5 axis CNC mill?

[Crazyswede]

Hey guys, has anyone thought about milling a case out of aluminum on a 5 axis CNC mill?

its a good idea but it might be kind of expensive

[allessence]

The idea of a strong gear case, coupled with a stronger gearing would be the best. But, since neither exist, next best thing would be to adapt something.

We all no the common failure points. Wouldn't it make sense to figure out which other gear MFG's might have something that is close? I mean close in overall layshaft length, maybe they are bigger stouter gears. etc.

Not sure, just was thinking about it. I for one, in all these years have only seen a handful of busted out rear cases. I have seen many with stripped teeth, layshaft bearing and shaft birnelling failures, few chains snapped, and then the pinion bearing failures which are often.

With the newer boxes it seems the 89-90 boxes have the best combo of longevity though the gears are narrower vs the 91-94 MY.

[allessence]

about cncing a case. If it could be made thicker it might be a good idea.

How about strengthing a case all ready produced? Cast aluminum offers some advantage as to billet and with the right stuff creates a stronger but less ductile case. Then there is chill casting, aging the alum chemically to induce hardness. etc.


I in my next life will come back in the late seventy's and be a transmission engineer at SAAB and will make there guys get it right. LOL>

[Hans]

Someone, somewhere on a forum (here?? in this thread, even??) wondered if an automatic box would be a good starting point. I've no experience with them, but whoever it was that suggested it thought that perhaps you could install some sort of non-Saab manual gear assembly. Does a 5-speed primary case bolt on to an autobox? I think, too, that the diff is separate from the gears on an automatic. (Clearly, I know zip about them...)