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we have an '88 SPG and its been making some weird sounds from the front of the engine. It makes a loud irregular(in frequency and volume) knocking sound when the clutch is engaged. when the clutch is disengaged, the sound goes away. Also, sometimes you will put the clutch in, shift into a gear, and something binds and won't allow things to spin, and it won't move. if you push the clutch in again and shift to another gear, in usually still won't move. if you put the tranny in neutral and engage the clutch, and then put it in gear it will move. the PO told us that there was something wrong with the tranny, 3rd gear apparently doesn't work.
I am feeling that it is something in the primary case, maybe a stuck tensioner allowing the chain to slap around and skip, or maybe even something is broken in there. what do you guys think? does this make sense? thanks!
 

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welcome to Saab Central.

In my opinion, you could drive your c900 500,000 miles or so (until rust do you part) and then put the primary-drive in another car and go another 500,000. I'd bet your issue is the transmission.(sorry)
 

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9008v said:
When you start to leave the clutch up, does the engine cut out?
yeah, that has happened a couple times. it almost sounds like something catches and causes it to stall. it will also, after a loud clunk, rev up a little and then go back to idle.
 

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Sounds like the pinion bearing has failed and the differential has locked or the tranny has gone into two gears at once.
 

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There is a small bit of linkage which prevents you from engaging two gears at once. Eg. 3 and 5. The crunch or grinding noise happens if you try to engage a second gear when there is already one engaged. If you take off the side cover (the one the dipstick is attached to) you will see what i mean. The solution is to engage 3rd very carefully, or else remove engine and gearbox, split gearbox from engine, strip gearbox, and replace the part. It is only a small part (and I'm not sure) but I think you have to strip the gearbox to replace it.

Another thing which might help: Both the gear lever and the gearbox linkage, when placed in neutral, centre opposite 3/4 gear. Make sure they both line up. To test this, put the gear lever in neutral, allow it to centre, and engage 3rd. If it engages without moving to one side it is ok. If it moves even slightly to one side it should be adjusted.
 

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Discussion Starter #7
i'm starting to think pinion bearing. that can be tested by pulling one of the covers on the tranny off and wiggling the shaft around, correct? i'm going to get some tube tomorrow and try to listen and see where it is.
also, with the clutch disengaged, i can feel the knocking through the pedal. the louder it is, the more i feel it.
 

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phishincruisin said:
we have an '88 SPG and its been making some weird sounds from the front of the engine. It makes a loud irregular(in frequency and volume) knocking sound when the clutch is engaged. when the clutch is disengaged, the sound goes away.
Clutch release bearing?
 

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phishincruisin said:
i'm starting to think pinion bearing. that can be tested by pulling one of the covers on the tranny off and wiggling the shaft around, correct?
Sometimes you can see or feel the damage to pinion bearings, sometimes not.
 

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Correct me if I'm wrong but doesnt the pinion bearing only make noise under load? This is in the driveway idling pushing down the clutch pedal no noise releasing the clutch pedal and then the noise starts.
 

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I've got a simular noise from my gearbox when the engine is idling and cold. If I rev a bit the noise goes away and the noise is less once it heats up/ gets lubed up. The noise definately comes from the front of the gearbox on mine, but the source could be further back.

Is your noise problem and the cutting out two seperate problems?
 

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SaabStory60 said:
Correct me if I'm wrong but doesnt the pinion bearing only make noise under load? This is in the driveway idling pushing down the clutch pedal no noise releasing the clutch pedal and then the noise starts.

This is a good point. The pinion doesn't start to rotate until the car moves. Is the noise there with the clutch engaged and neutral selected?
 

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When the pinion bearings are gone, all the gears in the stack on the mainshaft are loose too (especially 5th gear hitting the input shaft in the primary case); thus there is noise in neutral.

To check for worn pinion bearings, remove the 5th gear cover (the forward-most side cover). If the spacer behind 5th gear can be moved, there's play in the stack, thus worn pinion bearings.
 

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Jim Mesthene said:
When the pinion bearings are gone, all the gears in the stack on the mainshaft are loose too (especially 5th gear hitting the input shaft in the primary case); thus there is noise in neutral.

To check for worn pinion bearings, remove the 5th gear cover (the forward-most side cover). If the spacer behind 5th gear can be moved, there's play in the stack, thus worn pinion bearings.
Would that be the taper roller bearings at the output end of the shaft, or the cylinderical/needle roller bearing at the input end, or both?
What gives trouble too are the cylinderical/needle roller bearings on the layshaft. One of the gear teeth surfaces could also be after chipping, especially the '5th' gear.
 

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9008v said:
But then the cylinderical roller at the input end should hold '5th' gear steady?
The only thing that holds the gears "steady" is the nut at the 5th gear end of the shaft. If that nut, or the pinion bearing assembly on the other end of the shaft, is loose, all the gears are loose.
My (extensive) experience has been that the nut only loosens when the gear stack is assembled improperly or the pinion bearings fail.
 

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Jim Mesthene said:
The only thing that holds the gears "steady" is the nut at the 5th gear end of the shaft. If that nut, or the pinion bearing assembly on the other end of the shaft, is loose, all the gears are loose.
My (extensive) experience has been that the nut only loosens when the gear stack is assembled improperly or the pinion bearings fail.
Ok, I was mixing up the 4 and 5 speed boxes. But, I'm still confused, so phishincruisin probably also is. Which bearing do you think is gone and what do you check in the pic below.

 

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The mainshaft is at the top of the picture with the ring & pinion gears on the left.
The aluminum housing next to the pinion gear holds the pinion bearings.
On the far right on the mainshaft is 5th gear. There's a spacer right next to 5th gear, you can see it through the 5th gear cover on your transmission. If you can move that spacer in any way, without also moving the whole shaft including 5th gear, there's play in the gear stack. If there's play in the gear stack, the pinion bearings are already history.
Anyone buying a used transmission should check this. It's the only, albeit imperfect, way to check the bearings.
 
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