5 speed pinion shaft is longer? The plot thickens! Have found a diagram of the 5 speed box internals and compared it to a 4 speed and the pinion shaft does appear to be longer. I think you are correct. Therefore, would need to find a 4 speed box with a 3.67 final drive. Almost makes swapping over t...

The diff carriers in both those might be the same - you'll still have to take the entire box apart to swap the output/pinion shafts though. So you might just be able to put the internals of the newer box in your 99 case? You want to keep it a 4-speed? No interest in just putting in a 5-speed? Yeah,...

Sorry I meant the ring and pinion wheels in the rear of the box. I used it as that is what Saab call the ring & pinion in the list of gearbox ratios. Thanks! My box is from a 1980 99, G34601 and was hoping that I could slot in a 3.67 final drive from an 81-88 900 gearbox. The less I have to chan...

Does any one know if you can fit the final drive from any 900 box into a later 99 box or vice versa? Are the final drives a universal part?

Saab used a combination of hard and softer bushes in the rear axle to get the thing to steer under cornering loads. Dont ask me which was which, I would love to know! I was also told it might be better to use the early trailing arms, which I was told had shorter bushes and less location. Its someth...

Luke, where exactly was the chassis failing?

I think Luke uses a linkage with rose joints/heim joints (they have other names) at either end on his rally car. Looks like a mini panhard rod.

I'm going to use an adjustable arm with rose joints rather than the bushes on my 99 because I'm not a fan of the rubber bushes.

Geoff wrote:I suppose I could try that. Darn, now you've got me thinking!

You know you want to! One less bit for me to measure and draw up

How about measuring that replacement section and drawing it up in CAD?

Cars worth saving due to the special colour

I happened to have a flywheel drawn up in CAD so I had a little play around with what could be removed. Got it down to 6.1 kg/13.5lbs without the need for machining holes / deep recesses. Was still conservative so more scope for removing mass. People on UKSaabs took theirs to Puma Racing to have mac...

Drew my plan for the speed signal (for a non 900 application) was just loop back the tach output (58) to pin 39. The manuals show it as the same type sin wave. If you dont have a speed signal you will get base boost all the time as it effectively thinks that you are not moving. So doing this makes ...

The soccerball lug nuts have approx 19mm of thread enagaged. I would expect the conical nuts to have a similar amount.

Yep, the loads will derive from driving and braking torque and lateral corning force (also have forces from any bumps although the spigot should take most of it). If the inside of the wheel does not fit snug on the spigot then the studs will also support the weight of the car. On the 99, that genera...

This is rather interesting. May I ask how you determined the tensile load on each of the studs? What ksi did you use for the material and the safety factor? This part is just math, but the loads on the studs is what is the true driver. When you calculate the thread engagement length, you are determ...

Have done the math for thread enagagement of the 99 wheel studs for my build. For a 1/2-20 stud (assuming materials of same strength for both nut and stud), I calculated a thread engagement length of 11.06 mm. The type of thread does impact upon thread engagement length. Although, fine threaded bolt...