UKSaabs

To tell which primary a 900 gearbox has fitted i have been told that it is stamped on the box. But i cant see any numbers that define it. the gearbox has the part number lable just forward of the clutch inspection hole up top but the numbers on there dont seem to make any sense. Does someone have a photo to show where it is?

On the top of the primary case is an aluminium tag riveted on with what looks like a bar code on. Ignore this one.

Nearer the engine immediately behind it (and if it is still in the car, underneath a rubber hose) is another plate, usually yellow with a GM number on it. The third digit gives the type ie GM xxY xxx where the Y is the type number.

Thats great. I had been looking at the last digit on that yellow plate which explains why it didnt make sense. Cheers.

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)

Trackside wrote:type 8 will be just above 2500rpm ( very late models could be Ruby or LPT vert's)

'90 FPT non-S 3dr with type 8s here...

Never seen any definitive guide as to which cars had type 08 - it seems totaly random. I had a '91 3Dr FTP non-S with type 07.

Some old police cars in .fi had an 8 primary. :-)

Very elusive stuff. Someone should start remanufacturing those cog wheels so that more people could get them.

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..

Something is wrong there as both my 91 and 85 T16's did 70mph at around 2700 and all the LPT's, N/A's and 8v T's I've ever driven did it at 3000rpm. I even fitted type 7 box to an 8v turbo and it ran 2700 at 70 after previously running at 3000rpm. Also look in the handbook as it will give the mph per 1000rpm in top gear for the various models which tally with with my experience.

Hmm, interesting.

Not really sure what to say to that! Other than the fact that it is definatly on Type 7's now as opposed to the silly Type 6 before. And that other T16's I've driven have been close to mine butnot the exact same..? Have also driven a T16 with an 8 in and that was noticably lower revs again..

I suppose it all has to do with how accurate the speedo is, which does seem to be bang on in mine (with 16" wheels and fairly large tyres)...

Suppose it just show how each car is a bit different. Hmm

just thinking aloud, wouldn't it make a difference depending on whether the car was running on 15" or 16" rims as to what the difference in speed over the ground would be?

DAVLYN wrote:just thinking aloud, wouldn't it make a difference depending on whether the car was running on 15" or 16" rims as to what the difference in speed over the ground would be?

Not necessarily.

The standard 195/60 15 is almost exactly the same rolling radius as 205/50 16. 205/55 would give about 2.5% more rolling radius, pretty much within the margin of error of speedos and tyre brand/wear differences.

Size of wheel radius won't effect the relationship of the speedo to the rev counter - it will just make your real roadspeed vs your speedo wrong. Saab always build in an over reading on the speedo by about 2-3 mph ( which I think most manufacturers do as well). Maybe your speedo was a little on the slow side and this would be confirmed by it being the same as your GPS. On my NG900 it's certainly the case but there is a speed warning alarm you can set on the SID and this is bang on accurate and chimes in at 2-3mph above the speedo readout.

Trackside wrote:On my NG900 it's certainly the case but there is a speed warning alarm you can set on the SID and this is bang on accurate and chimes in at 2-3mph above the speedo readout.

Don't you mean below?

The type approval regs for speedos allow a certain amount of over reading, but no under reading, so speedos typically read high. A dead accurate SID bingly-bonger would kick in below the speedo readout.

If I set it at 70 it chimes when the speedo is reading 72/73 which is 70mph on my GPS and thus my actual roadspeed.

Trackside wrote:If I set it at 70 it chimes when the speedo is reading 72/73 which is 70mph on my GPS and thus my actual roadspeed.

So, yep, below the speedo.

Remember that final drive ratio's changed '88/'89

Early box with type 7 primarys will have top gear ratio almost exactly same as later box with type 8's

mmmmm, interesting

my t16 is originally an LPT (now apc'd), and while it originally had T6's, the (1st) replacement box was T6 (as is the current 3rd box .... but the 4th (ahem ) will be from a t16 with T8's)

thing is, i currently have some type 8's fitted that i sourced thru the classifieds here (£50..... BARGAIN ) and these have been verified againsts the pictures in emmetts' (excellent)thread over in the SC workshop.... and discussions on SC seem to suggest that LPT's and N/A's may have also had different gearing ratio's in addition to the primaries. some people were disscussing how their T8's seemed higher ratio'd than others (2500rpm at 80 compared to others near 3000 @ 80, which is closer to T7's)

Will check the codes this weekend, but my LPT runs a smidge over 3,000rpm at 70mph.....I assuming type-6's

Jope wrote:Very elusive stuff. Someone should start remanufacturing those cog wheels so that more people could get them.

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

Craig,

What is the verdict on your K Reg T16S? Type 8?

Paul

(always keen to see what Craig is up to with my old car, it's fair to say he's been busy with it since he bought it off me, was it about 3 years ago Craig?)