924Board.org

[Dave951M]

Since the Hall sensor on an 82 reads off of the teeth of the ring gear, is there a difference among model years as to the number of teeth on the gear? I have an 82 931, would the ring gears be different for the earlier YMs?
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Dave951M
86 951 Guards Red (Gone but not Forgotten!)
82 931 Guards Red (under construction)

[Smoothie]

I don't know if there's a difference in the number of teeth, but the '81-up 931 flywheel is different and not swappable with the earlier flywheel. Actually, you might be able to use and '81-up flywheel on a pre-'81 car, but definitely can't use a pre-'81 flywheel on an '81-up 931. As I recall, the teeth that the sensor reads are cut right into the flywheel and aren't on a seperate removable ring gear. The main difference and what the DITC ignition needs is an item called the "sintered metal insert". Earlier flywheels don't have it.

Actually, if I'm not mitakin', pre-'81 flywheels don't even have teeth. (All 931's have ring gear teeth mounted to the clutch pressure plate for starting.)
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Dave951M]

Well, I had a flywheel on an old 931 short block, but I'm not sure of the year or anything else about it. I was forced to hurry up and get the engine back in the car, but I'm not sure if the Hall sensor is going to read anything since I didn't see any studs protruding for the sensor to read (similar to the setup for a 944/51). That lack of a sensor stud has me a bit worried as to whether it had to be there, and if so, I'm facing pulling the flywheel back off after I've already put the engine back in the car. If it reads from the ring gear, I don't think there will be a problem.

You are correct about the ring gear on the pressure plate, but it is removeable. It's a tight fit, almost to the point of an interference fit. There are no teeth on the flywheel itself, but there are timing marks which I aligned with TDC on the crank and cam pulley, so all three read TDC at the same time. I didn't see anything to indicate whether the ring gear itself had to be timed in any way. I tapped it down onto the pressure plate, aligned the 9 bolts and torqued them down. I'm still hoping this is correct.
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Dave951M
86 951 Guards Red (Gone but not Forgotten!)
82 931 Guards Red (under construction)

[Smoothie]

You need the flywheel that has the teeth and the sintered insert. The insert is a metal piece that's (not suprisingly) -inserted- into a drilled hole in the outer edge of the flywheel. It's a permanent, non-removable piece.
Orientation of the pressure plates' ring gear doesn't matter - it's used by the starter only and not the ignition system. DITC reads off the '81-up flywheels' teeth and insert. If you have the correct flywheel, teeth will be visible through the bellhousing timing window.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Dave951M]

I think I may need a late flywheel.

Can the insert be seen somewhere on the flywheel?
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Dave951M
86 951 Guards Red (Gone but not Forgotten!)
82 931 Guards Red (under construction)

[Smoothie]

Yes.
A bit more about it here - http://www.924board.org/viewtopic.php?t=6563
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox