5-Speed competition gearbox.

[sonett]

The EMS is now off the road until the engine/gearbox is complete, stripped water pump and jack shaft have hurried it's rest to the garage.
The rest of the gearbox parts have arrived, so at least i can finish the box, just waiting on the UBV cylinderhead to arrive.
The gearbox will be a bit of a mongrel as far as parts are concerned, the main box is a chillcast from a 4-speed with a 5 speed primary housing. The final drive is a new special competition 5 speed 6:31, chillcast pinion housing, gear set from a 1989 900, type 4 primaries, this will give similar ratios to a 4 speed competition box, but just using 2nd to 5th. The selector shaft is a competition spec part with steel selector fingers and a quality universal joint. Short shift gear stick. The LSD is from Gripper Diffs and has been set up for tarmac. The clutch plate is a special light unit from Sachs tuning and motorsport, not available off the shelf, i wouldn't have usually chosen such a special clutch, but i will not be using any syncro rings with this this box, so the lightness will really help with the gears.


All i need to do now is modify the 5th gear selector shaft, with the competition fingers/selectors the 5th gear selector shaft is too long and this gets in the way of the 3/4th gear steel selector finger.
Because i have used the 4-speed chillcast box, the 5-speed layshaft cluster is a little too long, to get this to fit i had to remove a few millimeters from where the layshaft needle bearing sits, i removed the bulk of the aluminium in one go and slowly removed small amounts until i acheived a perfect fit with no play at all in the layshaft cluster, this took quite a while, the pictures hopefully make it clear as to what i had to do...



The initial pinion depth as stated on the end of the pinion is -15, i fitted a shim thickness of 1mm and checked it, it read -15 on the dial gauge, i must have checked it another 6 times and set up the gauge in the tool at least twice!
Here is the pinion with new bearings, the standard crush sleeve has been replaced by a solid sleeve, all sitting in the strong chillcast pinion housing...



This is really all you can see of the competition selectors in their position, the selection is very precise and very positive...



The clearance between the ring gear bolts and the internal selector shaft is very close and depending on the backlash adjustment, the bolt heads can even touch the shaft, to overcome this i just put the bolts in the lathe and took 2mm of the heads, i now have a clearance of 1mm between the bolt heads and the selector shaft.



This gearbox has had the syncro assemblies removed from gears 1 to 4, because the syncro rings/guide rings/springs and circlips have been removed there is a possibility the syncro hub can be moved to far, to stop this from happening the syncro splines on the gears need to be welded across two splines at three equally spaced intervals, all this is doing is replacing the space normally occupied by the syncro assembly, you can just see the welded syncro splines in the photo below...



The gears for this box are from a GM45612 gearbox (1989-90) and using the 6:31 final drive, but the intermediate gears have been swapped from an earlier 1981-1988 gearbox, this will give a much nicer spacing between the gears, in fact, using type 4 primaries will give very similar ratios in gears 2 to 5 as a competition 4 speed using special 30:35 primaries. I still have the option to change the primaries, but top speeds at 7000rpm will be around 100mph with type 4 and up to around 130 with type 8.

[steve99w]

I note on your photos of the assembled box, the selector dog is located by a roll pin, as i'm now pulling my 4spd crash box apart to find the other half of a DOUBLE roll pin that sheared in half, can you please confirm the diameter of the roll pin, and maybe sugest a solid steel pin so it will not break and cause you grief with a box full of neutrals or even chewed teeth. I'm using the same octaginal s&r dog..not the standard one.
Your comments would be greatly appreaciated

[sonett]

That is very unusual for the roll pin in the selector finger/dog to break, for that pin to shear there must have been a lot of force put onto it, maybe something else is not quite right in the gearbox. The fingers are really only guiding the selector forks into position, there will be some resistance, but only backwards and forwards. If there has been that much force put onto the finger, maybe it's good that the roll pin sheared?
I don't think a steel pin is a good idea, the roll pins have the ability to keep a certain amount of tension when fitted and this stops them from falling out, a steel pin cannot do this, you would maybe have to rely on loctite or something similar to keep it in place? Maybe use a hardened pin with threads on either end and nyloc's + loctite for piece of mind, but i still think this is extreme.
Another thing to maybe consider is the age of the roll pin and it's previous life or history, the Saab competition dept' had the luxury of stripping the boxes after almost every rally and replacing worn parts etc.
I can only measure an old roll pin as the new one's are in place, but they will be the same size as the standard pins, i'll have a look when i am next in the workshop.

[Ram85SPG]

hi sonnett,
can you give some details about the universal joint you used to replace the standard rubber coupler? i was thinking of doing this as well, how much does the selector/shift shaft have to be modified?
also i got the same short shifter as you in the group buy. installed it this weekend and "solidness" of shifting is greatly improved, along with the throw distance. i still feel the shifting could be better, and i think the u-joint might fix most of the remaining sloppiness.

[Jordan]

It looks like the u-joint from a 4-speed. But it could be just a generic one.. I'm sure any the right size would do.

Check the thread here

[Geoff]

I can't see the pictures at work, but... droool

[sonett]

hi sonnett,
can you give some details about the universal joint you used to replace the standard rubber coupler? i was thinking of doing this as well, how much does the selector/shift shaft have to be modified?
also i got the same short shifter as you in the group buy. installed it this weekend and "solidness" of shifting is greatly improved, along with the throw distance. i still feel the shifting could be better, and i think the u-joint might fix most of the remaining sloppiness.

The universal joint i have is very similar to the early Saab joint, but it is more substantial and quite a bit bigger, i got mine from Jorgen, but you can get them quite easily, they usually come with no holes drilled in them for the taper pin, so you have to copy what is on the original joint and put it on the new joint, you may have to make a bush, depending on what joint you get, here is fitted...


I did not get my shifter from the group buy on saabcentral, mine is from Jorgen Eriksson.

[Sean Tennis]

I note on your photos of the assembled box, the selector dog is located by a roll pin, as i'm now pulling my 4spd crash box apart to find the other half of a DOUBLE roll pin that sheared in half, can you please confirm the diameter of the roll pin, and maybe sugest a solid steel pin so it will not break and cause you grief with a box full of neutrals or even chewed teeth. I'm using the same octaginal s&r dog..not the standard one.
Your comments would be greatly appreaciated

If you look at the first photo you will see the shift shaft has 2 shift pawls. Saab ran into the shift pin issue also in their rally cars, so they shortend the 3rd & 4th shift fork arm (which tends to bend and was another issue this cured) and added the 2nd pawl, they also installed tampered shifter pins (and nuts) to secure the pawls in place, this way if one breaks-or the roll pin...- there is still 2 gears available-which gets one further down the road...and hopefully to the finish!

The pins will break on occasion, use new pins and change them out as part of maintenance, we toyed with adding a spot weld to the pawl, one could even drill a hole in the side of the pawl and weld there...or have pawl & shaft machined and install tampered shift pin...

[Sean Tennis]

We ran a few boxes without syncro's, I do not recall ever welding to stop shifter muff from moving to far.

We also removed ever other spline on the gear and muff (if I recall correctly) in one box to see if it would shift quicker and or easier, I don't remember it making a difference in our case... This was on standard gear sets and the turbo engine would blow 3rd gear in about 60-70 rough rally stage miles so transmission life was (very) short anyway.

Oh the fun we had....

[Geoff]

The universal joint i have is very similar to the early Saab joint, but it is more substantial and quite a bit bigger, i got mine from Jorgen, but you can get them quite easily, they usually come with no holes drilled in them for the taper pin, so you have to copy what is on the original joint and put it on the new joint, you may have to make a bush, depending on what joint you get, here is fitted...

It looks like at least one end has a straight through hole with a stud that would take a nut on either end? Does it use the taper pin on the other side? I tried making a u-joint shift coupler at one point but the OD of the joint was a lot bigger than the ones that SAAB sold and the pin would have been too short unless I ground the joint down a bit. I ended up just getting a good used one.

[sonett]

Jorgen had already made the holes for the taper pin on one side of the joint, all i need to do is line everything up on the other side and fasten it to the gear shaft.

[Luke]

Neat project. What are the differences in the tooth counts on the layshaft drive gears (the "5th" gear) from 81-88 and 89+? I never counted and if you already have the numbers it would be neat to know.

Also, why did you decide to eliminate the syncros? Do you think the faster shifting will make up that much time? Seems to be the big advantage of going to a syncroless dog is the ability to fit wider gears?

[sonett]

Neat project. What are the differences in the tooth counts on the layshaft drive gears (the "5th" gear) from 81-88 and 89+? I never counted and if you already have the numbers it would be neat to know.

Also, why did you decide to eliminate the syncros? Do you think the faster shifting will make up that much time? Seems to be the big advantage of going to a syncroless dog is the ability to fit wider gears?

I thought you rally guys would have had all the ratios, obviously not, i am a little surprised.
Your 5th gear statement of '89+?' tells me you don't work on gearboxes very often? The gears on the later boxes 91+ can only be used on those boxes.
The intermediate gear from 1980 to 1988 is 15/34, 1989 to 90 is 14/34, the 89-90 is stronger than the earlier gear, but i wanted that ratio and my car will probably have no more 200bhp and it is not a turbo, so i am happy with that.
6:31, 14:34 intermediate and type 4 primaries will give at 7000rpm;

1st 21.7mph
2nd 37.1
3rd 56
4th 77.7
5th 98

6:31, 15:34 intermediate and type 4 primaries will give at 7000rpm;

1st 23.1mph
2nd 39.2
3rd 61
4th 83.3
5th 98

as you can see with the 15:34 intermediate gear it gives a nicer spacing and just by changing the primaries i can increase my overall top speed.

I removed the syncro assemblies for a few reasons, quicker shifts and there is less to break, the car it will be going into will be used in race sprints/hillclimbs and the odd track day, with some of the circuits i will be at i expect to only use 3 gears, 2nd, 3rd and 4th, so with less gear changes and quicker gear changes, i hope to save some time.
Custom competition gear sets more often than not do not have syncros, so yes it enables wider gears, but at present there is not that much choice at a reasonable price, so for now this will suffice for my needs.

[Luke]

I thought you rally guys would have had all the ratios, obviously not, i am a little surprised.
Your 5th gear statement of '89+?' tells me you don't work on gearboxes very often? The gears on the later boxes 91+ can only be used on those boxes.
The intermediate gear from 1980 to 1988 is 15/34, 1989 to 90 is 14/34, the 89-90 is stronger than the earlier gear, but i wanted that ratio and my car will probably have no more 200bhp and it is not a turbo, so i am happy with that.

Thanks Sonett, I do have a spreadsheet with all the ratios at home, In fact Jordan has built some neat applets that we will put up on the website soon relating to gear ratios. You will be able to select any SAAB gearbox, chain ratio, tire size (including common rally and race tires) and redline, and it will calculate and graph speeds for that setup. We have also included the competition gearset and ring and pinions in the data. But for the purposes of discussion in this thread I was just wondering what the difference is in the input gear so other people could see and so I could sit here at work and think about it! I am well aware that 91-93 gearboxes utilize a different helical angle, but is the laygear input ratio different?

[Jordan]

I thought you rally guys would have had all the ratios, obviously not, i am a little surprised.
Your 5th gear statement of '89+?' tells me you don't work on gearboxes very often? The gears on the later boxes 91+ can only be used on those boxes.
The intermediate gear from 1980 to 1988 is 15/34, 1989 to 90 is 14/34, the 89-90 is stronger than the earlier gear, but i wanted that ratio and my car will probably have no more 200bhp and it is not a turbo, so i am happy with that.

Thanks Sonett, I do have a spreadsheet with all the ratios at home, In fact Jordan has built some neat applets that we will put up on the website soon relating to gear ratios. You will be able to select any SAAB gearbox, chain ratio, tire size (including common rally and race tires) and redline, and it will calculate and graph speeds for that setup. We have also included the competition gearset and ring and pinions in the data. But for the purposes of discussion in this thread I was just wondering what the difference is in the input gear so other people could see and so I could sit here at work and think about it! I am well aware that 91-93 gearboxes utilize a different helical angle, but is the laygear input ratio different?

Word.

I'll put it up soon, I don't know if your host supports Ruby on Rails (That's the platform I built it on , sort of like PHP)... Long story short, I'll either post it on my host or this one.