Saab 99 Rally Gearbox ratios re-manufacture

[simo96]

Ok I know that the Swedes have come up with a few different gearbox kits, but I need a set built to the orginal spec for my Historic cat 3 99 turbo over in the UK.
We have a worn dog box set that was fitted to Will Gollops rally cross car and the plan is to copy that set with one of the various UK gear manufacturers in a high grade material.
I think we could have 3 - 4 possible orders over here, but we would like to get the batch upto 10. I really would like mine before the end of the year, so we hope to get on with it asap.
We also have the 5.17 c&p and 4 sprocket drive that could be re-made.

[Jordan]

What are you estimating cost per set to be?

[simo96]

I would imagine it would be similar to the prices that you would pay for the Swedish sets. Until I take the set to the manufacturers this is unknown. I really am looking to see if there is a market for a small batch to be made then we will take it from there.

[Crazyswede]

I would imagine it would be similar to the prices that you would pay for the Swedish sets. Until I take the set to the manufacturers this is unknown. I really am looking to see if there is a market for a small batch to be made then we will take it from there.

Interested to see what the production costs are. I looked into it a few years ago with a local gear producer and it was close to $10,000 for the tooling. Not such a bad cost with 10 buyers though.

[Geoff]

I just watched a bunch of Will Gallop rallycross videos. It's understandable why the gear set is worn.

How close to original spec must the gear set be? Do the gears have to be helical or can they be straight cut? Crazyswede's comment about the pricing is due to the tooling costs for helical gears.

A bit off topic:
In this video at 4:45
http://www.youtube.com/watch?v=WdS4p6lPj0U
The commentator states that the SAAB and the Escort both use "the same Chevorlet Vega sixteen valve cylinder head." I'm guessing that Gallop's car has the SAAB 16v B head and the Escort has the BDA head which both look similar and look like a Vega head.

[nutcase]

Would love a set but out of my pricerange

[SwedeSport]

The only 16 valve on a Vega was the Cosworth motor. IIRC they were somehow connected with Ford and the Escort. or at least a few mechanics swiping drawings.

[simo96]

We can look at both setups, but I really would prefer helical. The company i am thing of using quoted me around £800 for a crown and pinion for teh V4 a few years back. This was based on 3 units being made. They will make one offs and generally do such things for vintage cars/racers (pre 1930's). One of the few companies over here that will do a total one off!

[Crazyswede]

All of the cost was in making the form for cutting the helical gears on the 1 piece 4 gear cluster. We might be able to reengineer it so that the gears assemble on a shaft but that also may reduce strength and reliability. A straight cut box wont have as much strength as the helical gears, it will make more noise, but it will be a lot easier to build. So lets see what your guy can do a helical set for.

[Geoff]

All of the cost was in making the form for cutting the helical gears on the 1 piece 4 gear cluster. We might be able to reengineer it so that the gears assemble on a shaft but that also may reduce strength and reliability.

You mean like this?

A straight cut box wont have as much strength as the helical gears, it will make more noise, but it will be a lot easier to build. So lets see what your guy can do a helical set for.

Straight cut gears themselves may be a little weaker than helical gears, however they don't produce thrust loads which cause the case to flex and the gears to push away from one another. Since we know the gearbox case is flexible and one failure mode is due to teeth losing good contact with one another due to flex of the case and possibly flex of the layshaft I'd think the 99/C900 gearbox would be a good candidate for straight cut gears, at least in a race car.

[Luke]

Geoff, I think thats exactly what Seth was talking about... the advantage of that style is that a conventional gearcutter could be used to make all of the gears. I talked to a gear shop about doing a set in the past and the proximity of the 2-3 gears creates a complication and requires more time consuming gear shaping equipment be used.

[DrewP]

Straight cut gears themselves may be a little weaker than helical gears, however they don't produce thrust loads which cause the case to flex and the gears to push away from one another.

Careful! Straight cut teeth don't generate axial thrust loads, but they certainly do still produce radial thrust loads, which still push the shafts apart, all geared drivetrains do. It's dependent on the pressure angle of the teeth.


We do some small gear cutting at work, mostly for low load things like optical slide stages, but even moderate sized gear cutters are pretty cheap, and there's no reason someone here couldn't do the brunt of the machine work ourselves and just have them finished by a gear shop.

The hard part with that setup would probably be cutting the splines, not the gears. The male side the splines come very close 2nd, they might have to be broached rather than point cut.

The female splines on the gears would take someone with a broaching head, which I don't have.


I did this at school, the spline was to mate to a Torsen T2 from a Miata that I built a chain-drive housing for, ground the cutter by hand and fitted it to a fly-cutting head. Took a while, but it worked.

http://www.youtube.com/watch?v=OG4nYuks ... AAAAAAASAA

[Luke]

My one un-answered question on a straight cut gearset on a SAAB is how is reverse going to work? On the helical gearset its kind of an ingenious way that they designed the idler gear to mesh with 1st gear and reverse. A new straight cut idler could still ride in mesh with 1st, but I have a feeling engagement of it into the reverse gear (which would likely have to be re-tooled as well) is not going to be as easy.

[DrewP]

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

[Luke]

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.