Strongest Gearbox Possible

[mmoe]

What if the gearset were a 4 speed that uses the 5 speed primary case? If we could move 4th gear where 5th gear resides, that leaves room for 3 much wider gears in the main case which could then be easily synchronized without compromising the width of the gears. The only hurdle would seem to be an intelligent redesign of the shifting pattern and shifting forks. The advantage is that 4th gear could be a 5th gear from a 5 speed, so we'd only need to design 3 gears with the appropriate ratio for the rear case and cut three gears into the cluster gear, which should result in a 25% savings in cost. This would also allow the use of the larger Saab pinion housing OR the smaller housing which fits a chillcast case without modification. The former would provide a shorter ratio R&P than the latter, though I've not looked at what 4 speed R&P ratios are to compare. I think the shifting pattern would be 1st in the lower left, 2nd in the upper middle, 3rd in the lower middle, 4th in the upper right (5th), and reverse as normal. A lockout tube could be added to the shifter fork shaft to prevent shifting into the omitted 1st gear location (upper left). How would that affect those who rally? For a daily driver it wouldn't bother me a bit personally.

[Jordan]

What if the gearset were a 4 speed that uses the 5 speed primary case? If we could move 4th gear where 5th gear resides, that leaves room for 3 much wider gears in the main case which could then be easily synchronized without compromising the width of the gears. The only hurdle would seem to be an intelligent redesign of the shifting pattern and shifting forks. The advantage is that 4th gear could be a 5th gear from a 5 speed, so we'd only need to design 3 gears with the appropriate ratio for the rear case and cut three gears into the cluster gear, which should result in a 25% savings in cost. This would also allow the use of the larger Saab pinion housing OR the smaller housing which fits a chillcast case without modification. The former would provide a shorter ratio R&P than the latter, though I've not looked at what 4 speed R&P ratios are to compare. I think the shifting pattern would be 1st in the lower left, 2nd in the upper middle, 3rd in the lower middle, 4th in the upper right (5th), and reverse as normal. A lockout tube could be added to the shifter fork shaft to prevent shifting into the omitted 1st gear location (upper left). How would that affect those who rally? For a daily driver it wouldn't bother me a bit personally.

There is some other car that is like that... they claim it gives a faster 2-3 shift which is what is used most and is beneficial for racing... e30 m3 maybe? Or a 190E Benz.. I remember on Top Gear somebody kept putting it into Reverse where 1st is supposed to be.

Early transmissions had a 3.89 (9:35) up through '81 and then went to the 3.67 (9:33) . Then back to the 3.89 ~ 1988. One of the sport & rally R&P was 5.17, not sure if this was the "big box". I don't remember the teeth count.

[DrewP]

There is some other car that is like that... they claim it gives a faster 2-3 shift which is what is used most and is beneficial for racing... I forget where I heard that.

Some Ferraris and racing Porches have shift patterns like that, with 1st down and left - I believe they call it a 'dogleg' shift pattern, since in most forms of racing you'd never actually use 1st except for coming in and out of the pits anyway - the 2-3 shift happens a lot though, less chance to miss the gate.





Drew

[Geoff]

What if the gearset were a 4 speed that uses the 5 speed primary case? If we could move 4th gear where 5th gear resides, that leaves room for 3 much wider gears in the main case which could then be easily synchronized without compromising the width of the gears.

I like the way you think! Sorting out the shift patterns and equipment for it (forks, any fork shaft changes, etc.) could start to become a development issue. I worry about other unknown issues as well... But I do like the idea.

[nkro]

The strange angle.

Thats on the orginal S&R helical gearset.
Its better to copy something that work.

Take to much time and money to develop something new.

Niklas

[mmoe]

What if the gearset were a 4 speed that uses the 5 speed primary case? If we could move 4th gear where 5th gear resides, that leaves room for 3 much wider gears in the main case which could then be easily synchronized without compromising the width of the gears.

I like the way you think! Sorting out the shift patterns and equipment for it (forks, any fork shaft changes, etc.) could start to become a development issue. I worry about other unknown issues as well... But I do like the idea.

I've got a pretty solid idea of how the shifter forks would work after some further thinking today. I'm pretty sure that it would not be difficult to produce some custom shifter forks, which would also hopefully eliminate the bent shifter fork issue as well. The 5th/reverse fork would be used as is, so we'd really only need a 1st gear fork with lockout for the old 1st gear slot and a 2nd/3rd gear fork that would basically be a shortened 3rd/4th gear fork. The 1st gear fork would also be positioned just in front of reverse since the synchro would now reside between reverse and 1st gear. I may do a mock up of the gears and forks next month to test the idea out. I'll just lathe out some aluminum "gears" without teeth and an aluminum cluster gear without teeth and see if it will work out as planned. Ideally, we'd be able to use the factory synchro rings, synchro muffs and synchro hubs to keep cost down.

The bigger issue I see is how the new gears would fit onto the pinion shaft and properly oil themselves. Keep in mind that there are oil passages that run from the pinion shaft to the sleeves/bearings that run inside of the gears. Those sleeves would need to be made for the new gears, with oil passages matching up. I don't think that's a big issue, but it is an issue needed to be addresses either way, as in with this concept or with a conventional 4 speed wide gear redesign. The latter would probably not require much effort in that the oil passages would still be used on the pinion shaft as is, but they would still need new sleeves/bearings designed so that part is the same either way. I'll have a closer look at the pinion shaft today and see if it will lay out properly. It may be that all that needs to happen is some new oil passage holes drilled into the pinion shaft and perhaps some sort of patch to the old oil passages (spot weld perhaps if it's not going to affect the sleeves/bearings). Maybe the old oil passages could even be left as is and new passages drilled for the new gearset.

[mmoe]

The strange angle.

Thats on the orginal S&R helical gearset.
Its better to copy something that work.

Take to much time and money to develop something new.

Niklas

I would generally agree, though the problem is that I don't have an S&R gearset to copy and I doubt I ever will. From that perspective, I'd still be doing just as much work designing it either way, since I don't have the S&R design available to take measurements from. Plus, I'd be constrained by limiting factors in terms of matching existing conditions while something new can be more flexible and allow for what tooling is available. No matter how you do it, making a gearset appear out of thin air is not going to be cheap nor fast. Time and money are a given either way.

[Crazyswede]

The strange angle.

Thats on the orginal S&R helical gearset.
Its better to copy something that work.

Take to much time and money to develop something new.

Niklas

I would generally agree, though the problem is that I don't have an S&R gearset to copy and I doubt I ever will. From that perspective, I'd still be doing just as much work designing it either way, since I don't have the S&R design available to take measurements from. Plus, I'd be constrained by limiting factors in terms of matching existing conditions while something new can be more flexible and allow for what tooling is available. No matter how you do it, making a gearset appear out of thin air is not going to be cheap nor fast. Time and money are a given either way.

There are a couple of those S&R gearsets floating around the members of this list. The problem with them is that there are not many of the proper ring and pinions available.

[Hans]

I recall reading (here?) that the S&R rings are from a van/truck -- Ford, maybe?? Of course, that leaves the pinion.

[DrewP]

What does the factory S&R splined output shaft look like? Does it have a removeable pinion stub, or is it one piece like the street parts?

Do the output cluster gears spline onto a regular 99 output shaft?

I ask because I think I've only ever seen photos of people's input clusters, and not the S&R output stack.


Drew

[nkro]

Sellholm here In sweden have the 6.31 for sale.

7.34 will only fit the large gearbox. And how many have a large gearbox.

Niklas

[99Super]

I recall reading (here?) that the S&R rings are from a van/truck -- Ford, maybe?? Of course, that leaves the pinion.

Interesting. I understand a local indy shop uses pinion bearings from a Ford PU diff (not sure the model) rather than the standard SKF bearings...

[mmoe]

I recall reading (here?) that the S&R rings are from a van/truck -- Ford, maybe?? Of course, that leaves the pinion.

Interesting. I understand a local indy shop uses pinion bearings from a Ford PU diff (not sure the model) rather than the standard SKF bearings...

They may be the same bearings in terms of universal bearing number. I bought some Timken M88048/10's from a guy advertising them for a Dana. Brand new for $1 ea. plus $5 shipping. :D

The SKF M88048/10s are a little different than everyone else's in that they have 19 tapered rollers instead of 18. In my experience, the extra roller doesn't really make any difference and the transmissions with 100k miles on Timkens look pretty much the same as those with SKFs as pinion bearing wear is concerned (those I've dismantled anyways). I've pretty much stuck to Timkens since as they are locally available and the SKFs aren't.

[speedysaab]

has there been any updates on developing a better gearset?

[s900t8v]

Recently found this thread, anything going on with this?