What's spinning in the drivetrain?
12-16-2018, 02:24 PM
#1
Drifting
Thread Starter
What's spinning in the drivetrain?
Car in Neutral
Clutch pedal released (i.e. not being pressed)
Which components from the rear of the engine all the way to the transaxle are moving in the above scenario?
1. release bearing (throwout bearing)
2. flywheel
3. pilot bearing?
4. torque tube?
5. etc?
Clutch pedal released (i.e. not being pressed)
Which components from the rear of the engine all the way to the transaxle are moving in the above scenario?
1. release bearing (throwout bearing)
2. flywheel
3. pilot bearing?
4. torque tube?
5. etc?
12-16-2018, 03:27 PM
#3
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The pilot bearing would be spinning with the crank but so is the short clutch shaft so the bearings are not spinning in the race. It only has to work when the clutch is depressed and the clutch shaft stops turning. The by far most common source of a whine will be torque tube bearings. In my limited experience 
12-16-2018, 03:41 PM
#5
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Every gear in the transmission is also turning, except the pinion.
The most common source of noise, with the clutch released is the bearing on the input shaft (which is 5th gear.) The second most common failure are the bearings in the torque tube.
The input shaft (5th gear) bearings were especially "weak" in the transmissions frim 1978-1984. They were changed to larger, longer lasting, more stable, stronger bearings in 1985, and again in 1987. The larger 1985/1986 bearing can be used in the pre-1985 transmissions with some machine work. Thus is a very common modification, for me to make, when rebuilding these transmissions.
The most common source of noise, with the clutch released is the bearing on the input shaft (which is 5th gear.) The second most common failure are the bearings in the torque tube.
The input shaft (5th gear) bearings were especially "weak" in the transmissions frim 1978-1984. They were changed to larger, longer lasting, more stable, stronger bearings in 1985, and again in 1987. The larger 1985/1986 bearing can be used in the pre-1985 transmissions with some machine work. Thus is a very common modification, for me to make, when rebuilding these transmissions.
12-16-2018, 04:44 PM
#6
Three Wheelin'
Every gear in the transmission is also turning, except the pinion.
The most common source of noise, with the clutch released is the bearing on the input shaft (which is 5th gear.) The second most common failure are the bearings in the torque tube.
The input shaft (5th gear) bearings were especially "weak" in the transmissions frim 1978-1984. They were changed to larger, longer lasting, more stable, stronger bearings in 1985, and again in 1987. The larger 1985/1986 bearing can be used in the pre-1985 transmissions with some machine work. Thus is a very common modification, for me to make, when rebuilding these transmissions.
The most common source of noise, with the clutch released is the bearing on the input shaft (which is 5th gear.) The second most common failure are the bearings in the torque tube.
The input shaft (5th gear) bearings were especially "weak" in the transmissions frim 1978-1984. They were changed to larger, longer lasting, more stable, stronger bearings in 1985, and again in 1987. The larger 1985/1986 bearing can be used in the pre-1985 transmissions with some machine work. Thus is a very common modification, for me to make, when rebuilding these transmissions.
12-16-2018, 06:25 PM
#7
Nordschleife Master
As noted, the pilot bearing is not 'turning'. The entire thing is rotating, but the bearing parts are not spinning relative to each other. It only spins when the clutch is released and the short shaft stops.
Flywheel, connected to the intermediate plate & pressure plate. Throw out bearing spinning all the time.
Clutch discs contacting the intermediate plate.
Short shaft splined to the discs.
Torque tube clamped to the short shaft. TT bearing spin when it does.
Trans input (5th gear) clamped to the TT,
All the gears meshed with the input shaft. All the gears spin all the time. It's the 'dog gears' that engage in different ways that decide how the output shaft will spin relative to the input. Any good description/drawing of how a synchro mesh trans works will show this.
I thought about writing this so it would synch up with "Dem Bones", but that would be silly.
Flywheel, connected to the intermediate plate & pressure plate. Throw out bearing spinning all the time.
Clutch discs contacting the intermediate plate.
Short shaft splined to the discs.
Torque tube clamped to the short shaft. TT bearing spin when it does.
Trans input (5th gear) clamped to the TT,
All the gears meshed with the input shaft. All the gears spin all the time. It's the 'dog gears' that engage in different ways that decide how the output shaft will spin relative to the input. Any good description/drawing of how a synchro mesh trans works will show this.
I thought about writing this so it would synch up with "Dem Bones", but that would be silly.
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12-16-2018, 06:47 PM
#8
Team Owner
Most of the noise in this driveline is coming from the transmission and their is a clear whine as the car moves through 123 gears
This is where the load is highest
the sound is consistent with worn bearings causing the gears to move out of their original position causing a whine
in addition their is a rotational noise while the transmission is in neutral and the clutch pedal is released and the engine is idling
The torque tube has minor rotational noises
i will suggest the trans be sent to Greg Brown for rebuild and the TT be sent to Constantine
The TOB appeared to run quietly
12-16-2018, 07:36 PM
#9
Drifting
Thread Starter
Thanks all, especially to Stan who has seat time in this car. I’m just trying to piece everything together in my head before I determine where I want to put my priorities with the car. Funny enough, I hear the rotational “whirring” noises the most, which was the genesis for this thread.
I didnt think it was likely a pilot bearing, but I thought I had better double check. Unfortunately replacing the pilot bearing would be much easier than getting at the torque tube. Such is the life of shade tree Porsche mechanic.
I didnt think it was likely a pilot bearing, but I thought I had better double check. Unfortunately replacing the pilot bearing would be much easier than getting at the torque tube. Such is the life of shade tree Porsche mechanic.
12-16-2018, 08:23 PM
#10
Chronic Tool Dropper
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Good news is that the torque tube bearings replacement is relatively simple once you have the gearbox out for the input shaft bearings. Plus all the other wear parts WYAIT. It's a slippery slope.
12-16-2018, 09:10 PM
#11
Drifting
Thread Starter
WYAIT is an evil temptress, isn’t she? 
12-17-2018, 01:31 PM
#12
Chronic Tool Dropper
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She is, but she's also the Goddess of Happiness when it comes to keeping older cars reliable and safe enough to drive.
My time-eating WYAIT habit starts off with a little cleaning around whatever I'm looking at, followed by a parts list for everything I see nearby. Rinse, repeat. Literally. Every funny noise has a cause, and that cause has friends lurking nearby.
My time-eating WYAIT habit starts off with a little cleaning around whatever I'm looking at, followed by a parts list for everything I see nearby. Rinse, repeat. Literally. Every funny noise has a cause, and that cause has friends lurking nearby.
12-17-2018, 01:33 PM
#13
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They virtually "jump" out of the car, compared to an automatic torque tube.
12-17-2018, 07:21 PM
#14
Chronic Tool Dropper
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??? But he was going to remove the transmission to replace all the noisy bearings anyway.
12-17-2018, 07:39 PM
#15
Drifting
