Awh man, blew another transmission

[Nate]

Once a box blows gears is it rebuildable? Does a case ever reach the yield point where it plastically deforms besides when it cracks?

[DeLorean]

well what ever parts are still in-tact may be re-used, but I would not call a box that has blown a gearcluster "rebuildable" because you you basically need a parts gearbox in order to fix the one with the stripped gears.
see this picture--



If you have lost Part 33, 36, 37, 39 (most common) good luck getting those without a parts gearbox that has good ones in there... but in that case that's probably the gearbox that should be rebuilt, not the one with blown gears.

[Nate]

Yes, I'm very familiar with that picture. My question really is why do Saabworks cars have bigger gears if the case is causing gear failure? If the case was flexing why didn't they strengthen the case instead of the gears?

[Luke]

The case flexing causes ring/pinion failures. Dosen't have a damn thing to do with 3-4 gear failures in my opinion. Those failures are just from narrow gears and too much torque.
Thats why if you look at a competition department prepared box you can see the only reinforcements they made to the case were in the differential area.

[Nate]

The case flexing causes ring/pinion failures. Dosen't have a damn thing to do with 3-4 gear failures in my opinion. Those failures are just from narrow gears and too much torque.
Thats why if you look at a competition department prepared box you can see the only reinforcements they made to the case were in the differential area.

So even if the case was made from iron we would still see 3-4 gear failures

[DeLorean]

I also think that the age of the box has something to do with it. Most of the lower mileage boxes I have had have lasted longer than the good rebuilt (but higher mileage) boxes I have had. Perhaps the thousands of heat cycles weaken the gearclusters throughout their lifespan? This is just a guess but I could see it being a possibility. Oil quality and how often it's changed CLEARLY does play a major role in gearbox life. I took an 86 turbo box apart that still worked at 200K, but the gearclusterd had so much wear and pits that I think if that car actually had boost (which it hadn't for the last 20K) it would have blown those gear clusters immediately.


I think it's pretty clear that if the gears were physically stronger, this would eliminate one of the most common failure items on these transmissions... You really can't make them any larger being that syncros and gears can't occupy the same space at the same time, there is a limited amount of room in the gearbox.

At that point it would be a matter of adding an extra bearing at the top input shaft and some diff housing reinforcements to make a "bulletproof" gearbox. It's really a shame we can't get someone to make us some gears for a reasonable amount, it would go a long way toward making these transmissions a lot more reliable in high HP/high torque applications.

[Crazyswede]

I think if the gear boxes were stronger they probably wouldn't break as much

[Jordan]

Somebody being able cut a stronger gearset I think would benefit a lot of people. It's too bad that it takes a relatively large amount of capital to do this. Since the transmission used beyond stock environments is definitely the weak point of the 900/99 which spanned over 20 years of production and over a million vehicles, you would think there would be some demand. Yeah, yeah, saab owners are cheap...but as they turn into more recreational vehicles, maybe people would be willing to part with some extra dough.. I'm just thinking out loud.

The nice thing is that we even have S&R boxes to work off of.

[Geoff]

We don't need no stinkin' synchros.
The S&R boxes were dog boxes and crash boxes. I don't know how many people would feel about driving a recreational car with one of those boxes. (rally car, yes. Daily summer driver.. I don't know, I've never driven one of those boxes...) But that's really the only way to make the gears bigger (taking up the space where the synchros used to be).

[DeLorean]

I think if the gear boxes were stronger they probably wouldn't break as much

ha, why didn't I think of that!...

[Luke]

Mongo has special talent

[Crazyswede]

Mongo has special talent

[DeLorean]

Somebody being able cut a stronger gearset I think would benefit a lot of people. It's too bad that it takes a relatively large amount of capital to do this. Since the transmission used beyond stock environments is definitely the weak point of the 900/99 which spanned over 20 years of production and over a million vehicles, you would think there would be some demand. Yeah, yeah, saab owners are cheap...but as they turn into more recreational vehicles, maybe people would be willing to part with some extra dough.. I'm just thinking out loud.

The nice thing is that we even have S&R boxes to work off of.

All excellent points... It just takes 1 person to get the ball rolling At least some of the trouble with this is that anyone who owns one of the S&R boxes already has a very sout gearbox, they might not be very likely to loan out it's internals in order for someone else to attempt to copy them... Personally I don't know anyone who's got an S&R box, but if I did I would be willing to pay quite a high price for it

[Crazyswede]

I'll repeat it again. When I sent a picture of the cluster gear to the local gear maker I was informed that the guide to make the teeth was going to cost about $7000 and the cutter another $1200. I don't know what the cost was on anything else. I would wager if we went that route that the first gear set could easily cost $10,000 to $12,000. After the initial tooling costs they would become much cheaper but you would still want to get at least 10 preorders before investing. The other problem would be the risk that they wouldn't work correctly and then you have a lot of unhappy people. We could design a crash box much more easily.....it would be harder to shift but it would be very strong.

[Jordan]

In my mind this is possible:

A close ratio 5 speed with gears 1-4 with synchro-less, straight cut gears and a helical 5th gear.



I've also been reading around and many people have commented that straight cut gear boxes are not as noisy as most people assume they are. Also, I think for me it would be less of a strength issue (N/A b-mota) and more an issue of getting some nice close-ratio gears, with a decent top speed.

I wonder how much it would cost to reproduce something like the speedparts cluster...the dollar as poor as it is + shipping + overhead, there must be something we could do.