[OregonSaab900s]

Hi,

I’m working on my 89 900 NA, this car does not have 1st, 2nd. I does have 3rd, 4th, and reverse. Maybe has 5th… either way I posted about this a while ago and let the car sit in the field. Now I’m back to the project and by the way, it shifted smooth in all gears until the problem developed instantly and the car was parked.
Previously I was told that it is most likely the rubber coupling between the trans and the fire wall. Well from what I inspected, I do not think the coupling is bad. This is a video I recorded where you can see the shaft on the firewall and the shaft on the trans move in unison.

second video is showing entirely the neutral range of motion. The shaft almost nearly doesn’t rotate at all. While the shift lever does not self center. This makes me think that there is a bushing that the lever pushes against and that bushing has broken. When I took the shifter lever out of its socket it visually looks fine. Though I might swap the one I have in my other car. Either way if you have advice after watching the videos that would be great! I’m concerned as the bushings are pretty much non existent online, though I do know a guy in Oregon that probably has some used parts.

Neutral range of motion

youtube.com

 

[mylesc]

Changed my reply, just read that "...it shifted smooth in all gears until the problem developed instantly and the car was parked." Sounds like a broken shift centering spring inside the transmission but you should be able to still get 1st and 2nd. Did someone overpower the reverse locking mechanism to start the car?

 

[OregonSaab900s]

Changed my reply, just read that "...it shifted smooth in all gears until the problem developed instantly and the car was parked." Sounds like a broken shift centering spring inside the transmission but you should be able to still get 1st and 2nd. Did someone overpower the reverse locking mechanism to start the car?

No, the problem quite literally happened instantly while driving. It quite literally cannot engage 1st or 2nd no matter what. I’m still convinced it’s a bushing because if I push the selector to reverse, it will spring back toward center.

 

[mylesc]

In a C900 with internal shift centering (basically all from about 1986 on) the only thing that makes the shift lever return to neutral from any gear is the internal shift centering spring. Without that spring the lever would just flop around anytime it's not fully engaged in some gear. That spring has two legs, one on each side of a steel finger and the resting position between the two legs is where the 3-4 gate is.

So with a good spring shifting left of neutral (the 3-4 gate) uses one side of the spring and shifting right of neutral uses the other side of the spring. When those springs break it's always just one leg. So in your case the part of the spring that causes the shift lever to return to neutral from fifth and reverse is still intact while the other side that snaps the lever to neutral from 1st and 2nd is broken.

This is an issue that arises instantly when the spring breaks. It doesn't explain why you don't have 1st and 2nd, you should be able to engage those by just moving the lever as far to the left as it easily goes and then pushing forward or pulling back like normal. Possibly you are mistaking the 3-4 gate for the 1-2 gate? I'd suggest, with no gears engaged move the lever to the right until you just bump against the resistance of the spring. That's the 3-4 gate and you should be able to engage those gears at that location by just pushing forward or pulling back. Then disengage and go back to that point (rightward until you touch the spring) and then move the lever to the left as far as it goes and see if 1 and 2 can be engaged.
There are other possibilities but with the information you've provided this is very likely the problem.

 

[OregonSaab900s]

In response to this, I want to look back to the second video I attached to my original post. Moving the gear selector in the neutral position side to side gives absolutely zero movement on the shaft into the trans. It may be difficult to see, but there is no movement in the entire neutral range UNTIL I lift the reverse lock out and push it into reverse. My theory is that the rubber bushing has worn and split, so the shaft to the trans comes back to center, but how the lever in the car goes to the ring socket, it only pushes the shaft side to side since the bushing is blown. The bushing is probably still slightly attached for going into reverse. Going to post an update to this soon to rule out the gearbox self centering! I have a decent idea on how to test that.

 

[mylesc]

You can shift the transmission into all forward gears by just grabbing the rubber coupling and manipulating it directly (the shift lever must be unlocked). You won't be able to get reverse as the retractable pin in the shift lever will prevent the coupling from rotating far enough to get reverse. If you do that and the coupling springs to a single, central location from both rotational extremes then the internal centering spring is OK. If you can rotate the coupling either way without feeling the resistance of the spring then the spring is broken.
If you just push the coupling forward that's 3rd. Pulling it back gets 4th. Rotating it fully CCW (as if viewed from the driver's seat) and pulling gives 1st and pushing gives 2nd. Rotating fully CW from the central point and pulling it back gets 5th. (Push/pull motions are reversed from shift lever actions.)

 

[OregonSaab900s]

Ah the culprit! Found this just sitting at the bottom of the lever socket.

 

[OregonSaab900s]

Looks like the plastic has cracked and it must have popped out.

 

[OregonSaab900s]

Anddddd the other bushing is toasted too.

 

[mylesc]

Well, that's a new one on me.

 

[OregonSaab900s]

What really sucks is the black rubber bushing is NLA on any site I’ve searched. Hopefully I can get a used one.

 

[Cornbinder89]

worse case, you can make one out of Durlin or similar material. It will transmit more vibration but would get it shifting again.

 

[OregonSaab900s]

worse case, you can make one out of Durlin or similar material. It will transmit more vibration but would get it shifting again.

I’m almost thinking about making a silicon mold once I get my hands on a good one to make more copies. Or I can pull the one off my other car and use it as a mold. It would be awesome if another car (Toyota, Chevy, etc.) had something similar.

 

[Cornbinder89]

No first hand experience, but two things come to mind. One is that silicon may be too soft for that application. The 2nd is that I provided some samples for a guy who was going to make new rubber parts for old trucks. He was an experienced prototype man for one of the big three automakers, so had some experience. He found that making small runs out of urethane was very hard to do. The material was hard to get and keep fresh and even when molded in a vacuum, had trouble with air inclusions.
I think urethane is the durometer you would want for that application.
Durlin is hard and machinable but not so good at dampening.

 

[jvanabra]

I think Durlin = Delrin, and yeah, that's probably what I would use. Even nylon is probably fine. However, one think to keep in mind is that Saab built some slop into the shifter, it seems to keep it easy to shift when motor mounts are stressed or worn. We took all the slop out of the race car (lots of Delrin) and replaced the coupler with a metal tube and the car was largely unshiftable. IDK where the sweet spot is, but somewhere between factory and what we did.

 

[OregonSaab900s]

From what I can tell, this would be near perfect.

 

[Jim Mesthene]

I saw that happen once. It was on a new car. Friction from the shift rod pulled it out.
I put the bushing back in with a spot of 3M Weatherstrip adhesive and lubed the rod w/ silicone paste.
I think the old bushing would work fine in this case.

 

[Cornbinder89]

Jvanbra, thanks for the spell correction, i showed as correct, but never ask me how to spell anything, I'll tell you how I spell it, not how the rest of the world spells it!
Oregon, all I can say is try it and see. I just relayed the problems that they guy I lent my stuff too had. He was trying to reproduce 80 year old rubber parts in urethane, and was no novice. As I said, he worked in the prototype dept of one of the big three automakers and even new how to make formed safety glass windshields by hand. The problem he had was not the molds or the design but will the material.
A bushing that is too soft will deform and wear quickly, not provide the correct alignment of the linkage, one that is too hard will transmit noise and vibration.

 

[OregonSaab900s]

So my newest problem with this idea… it looks like the collar for the gear lever is welded on AFTER the bushing is put on the shaft. Or maybe it’s put on in a different way, but that’s what I can tell. Jim mentioned that he had one break and he used 3M tape to attach it again, maybe that’s what I will have to do, or I grind the collar off and re-weld it on, but I fear I might risk having a misalignment of the shaft…

 

[Jim Mesthene]

It's a split bushing.
It's made that way so it can be installed. The rubber bushing around it, and the shifter housing hold it in place.