UKSaabs

McVities wrote:been wondering about this.......would motorcycle cogs and drive chains work? Might give a bit more choice for the exact ratios wanted, either track day lunacy type 4's or econo-cruising type 8.5/9's :D

I'm afraid that the cogs are a custom part. There are three parallel chains, but the cog teeth have been machined into the same lump of iron. We just dismantled a gearbox with my friend yesterday, so I can take pictures of the primary at the garage later today if I remember.

Nothing impossible to make though, but I guess you'd have to order quite a few to make it worthwhile.

Another interesting angle on this is the way the power is delivered on different models. My NG900 has what apperars to be the same 5th gear as my old c900 T16 but it doesn't pull as hard when you put your foot down at 70 due to the way the T5 engine management has moderated the midrange power - I have to drop down a gear to pull hard even with stage 3.

Going to have a look at my G reg carly and K reg this weekend so will report back on which they have. Both the same i would presume. type 8s would be a nice thing.

Jope wrote:There are three parallel chains, but the cog teeth have been machined into the same lump of iron. We just dismantled a gearbox with my friend yesterday, so I can take pictures of the primary at the garage later today if I remember.

will save you the trouble, here one shamelessly stolen from an ad in the classifieds



Now although the cogs are indeed all on the same piece of metal, is there a need for this to be replicated? Surely as long as the cogs are fixed very securely (bolted/welded) so they all turn together, there isn't a problem.........coupled with a wider steel primary housing, they could be made thicker, and therefore stronger

Jope wrote:Nothing impossible to make though, but I guess you'd have to order quite a few to make it worthwhile.

why should it need to be made? Think we could pass this to some motorcycle enthusiasts......in the big wide world of bikes, there must somewhere be a set of cogs with the right properties, just need to find them and bolt it all up

McVities wrote:Now although the cogs are indeed all on the same piece of metal, is there a need for this to be replicated? Surely as long as the cogs are fixed very securely (bolted/welded) so they all turn together, there isn't a problem.........coupled with a wider steel primary housing, they could be made thicker, and therefore stronger

I'm curious as to why you think you need to make them stronger Rich?
Not a common failure of c900 boxes (the primary chains) afaik.

G

saabstudent wrote:I'm curious as to why you think you need to make them stronger Rich?
Not a common failure of c900 boxes (the primary chains) afaik.

at the moment I'm exploring possibilities, probably the original chains are good enough....but I don't know how far they are rated. Think I may have seen a rally box with quadruple chains and thought 'thats a handy bit of kit'.
It's all just thoughts in my head, mainly turning into plans for my rebuild/restoration.....I know that there are many different points of possible failure within the gearbox that make the unit as a whole the major problem for a tuned c900. I don't know about going for a lottery-winners spec box, but if the car ends up with as much power and torque as I'd like, it will need something pretty special. I also figure that if the box is going to have to be built up out of pricey bits, then I'll do everything properly 1st time round - in an attempt to give it some longevity, and save hoisting it out every week......it'll probably still die spectactularly!!!

Ok both my 900s have type 7 primaries. K reg and G reg turbos. the codes are GM55706 and GM55704. Does anyone know why the last digit is different between the two cars?

McVities wrote:

saabstudent wrote:I'm curious as to why you think you need to make them stronger Rich?
Not a common failure of c900 boxes (the primary chains) afaik.

at the moment I'm exploring possibilities, probably the original chains are good enough....but I don't know how far they are rated. Think I may have seen a rally box with quadruple chains and thought 'thats a handy bit of kit'.
It's all just thoughts in my head, mainly turning into plans for my rebuild/restoration.....I know that there are many different points of possible failure within the gearbox that make the unit as a whole the major problem for a tuned c900. I don't know about going for a lottery-winners spec box, but if the car ends up with as much power and torque as I'd like, it will need something pretty special. I also figure that if the box is going to have to be built up out of pricey bits, then I'll do everything properly 1st time round - in an attempt to give it some longevity, and save hoisting it out every week......it'll probably still die spectactularly!!!

No problem using my photo's, here is another one you can steal
The primary gears are really quite strong and so are the chains, as long as they are not too stretched and worn, the weak point is the aluminium spigot that the top gear fits on, with high power/torque and abuse, this can shear. On the early 99's the primary drive was cogs and a shaft, even on standard cars these could fail, hence Saabs change to sprockets/chains. This is the front cover from Will Gollops 99 4-speed rally cross box, this had 4 chains and a grafted on bearing to give extra support.

Craig wrote:Ok both my 900s have type 7 primaries. K reg and G reg turbos. the codes are GM55706 and GM55704. Does anyone know why the last digit is different between the two cars?

The last two digits refer to the development of the gearbox.

GM55704 is from a T16 and will have gears designated to the 1989-90 gearbox.
GM55706 is also from a T16 but with cat and also 900i and 2.1 and has gears designated to the late box 1991- 1993.

I am about to start my stash of spare gearboxes for the Chavmeister so as I scrap some of the cars in the garden, I shall be taking out known good boxes.

As I have no idea whether the boxes in the cars are original, and particularly when I have a pile of removed boxes, is there a full list of c900 gearbox types that those two come from? It would be most useful...

5th gear on mines does 30mph @1000 rpms IIRC, I will take a picture the next time I do 70mph to double check what type 8 do, I need to buy a Tom Tom to really know for sure what the speed is though.

McVities wrote:Now although the cogs are indeed all on the same piece of metal, is there a need for this to be replicated?

Yes there is. The pictures I'd have provided, but naturally forgot to take would have illustrated the construction of the upper cogwheel assembly.

There is a large bearing + loose circlip inside the cogwheel that are held in place with another circlip on the inside edge. You will need to make a similar construction, else you will need to invent your own fittings for the cog.. I personally am not interested in that kind of approach, I just want an 8 primary, not hours of metalwork..

TFatC wrote:I am about to start my stash of spare gearboxes for the Chavmeister so as I scrap some of the cars in the garden, I shall be taking out known good boxes.

As I have no idea whether the boxes in the cars are original, and particularly when I have a pile of removed boxes, is there a full list of c900 gearbox types that those two come from? It would be most useful...

Nick, just post up the gearbox codes of what you find and i'll try to help.
Basically there are 4 types of gears fitted to the 5-speed C99/900, up to 1980, 1981-1988, 1989-1990 and 1991-1993. Final drives are 9:33 up 'till 1988 and from 1989- 9:35.
Then there are the primary gears, type 4= 31:30, type 5= 30:27, type 6= 31:26, type 7= 32:25, type 8= 33:24. To add to this there are quite a few motorsport primary gears and final drives, both 4 and 5 speed.

just back from a drive in the car on work duties......

with my LPT source 5spd, and Type 8 Primaries, at 2500rpm the sat nav was reading 62mph

The answers to the majority of questions in this thread have been on Widde's site for years.

http://900aero.com/main/tech_main_tranny.htm

Thanks Si, I keep forgetting about this great site

si wrote:The answers to the majority of questions in this thread have been on Widde's site for years.

http://900aero.com/main/tech_main_tranny.htm

I forgot about that as well, I think I have the tallest gearing on my 900


Year Model Gearbox number Final gear Total gearing 1 2 3 4 5 reverse

1990 900 T16 GM55804 9:35, 3.89 12.88 -7.49-4.91-3.55-2.83 -R 14.17

ShadowWorks wrote:I forgot about that as well, I think I have the tallest gearing on my 900

Year Model Gearbox number Final gear Total gearing 1 2 3 4 5 reverse

1990 900 T16 GM55804 9:35, 3.89 12.88 -7.49-4.91-3.55-2.83 -R 14.17

<waves> Same as mine.

£500 for a perfectly respectable, MOTd black 3dr T16 with type 8s? I reckon I paid for the primaries & leather and got the rest of the car free...

MrMoonyMan wrote:

Trackside wrote:You can tell by how many revs you are doing at 70 = type 6 will be near dead on 3000rpm ( nearly all LPT's and N/A cars) , type 7 will be about 2700 rpm ( 16v Turbo with APC) and type 8 will be just above 2500rpm ( very late models could be Ruby or LPT vert's)

Sorry, I gotta disagree here, my T16s is running on a type 7. At 3000 in 5th it is bang on 70mph on both the Speedo and GPS..Had it on Type 6 before and whilst the acceleration was hilarious I felt it was pretty unusable as a motorway car - didn't help that I had no roof lining then either of course!

Here it is with the Type 7 in France somewhere..

This looks spot on to me

This how I think works out in theory for later box at 70mph in 5th with 195/60 15 tyres
Type 6: 3256 rpm
Type 7: 3037 rpm
Type 8: 2824 rpm

If anyone's put type 8's in an earlier (up to '88) box then it should be 2639 rpm but no cars supplied from factory like this. Probably a touch too tall

My old 91 T16 must have been type 08 then after all