924Board.org

hayeslewis · Joined: 21 Aug 2011 Posts: 74 Location: Alexandria, VA

Please take a look at these two. I can't figure out how to make a post imbed a photo anymore. I tried Google photos, Amazon, and Imgur

https://imgur.com/Zv11B29

The rusty friend here came out of my other 924 race car, (Red-Might become a prod racer) the clean one came out of my 924 ITB car.

The red car has a snail shell, though i really can't tell if it's a snail shell from a turbo or a NA.

So....

Does anyone know why these two look different and have different part numbers? does it matter? I looked at the 76-79 PET and the 80-85 PET. They have the same part number listed for all the clutches; 4spd, 5spd, Audi, G31... But when I do online searches the interwebs seem to believe that a 931 clutch is not compatible with a 924 clutch. The splines are the same, the measurements seem to be the same...

Bonus points for explaining why the center cracked and the springs fell out. There was a little gap (3-4mm? on the top of the torque tube where it met the bell housing. Previous owner over-torqued the top bolts connecting the torque tube to the bell housing. Could a slightly miss aligned drive shaft lead to the failure? Pilot bearing isn't seized-but will get replaced.

Thanks in advance for all the input.
_________________
Hayes Lewis
1979 924 HP
1979 924 ITB/HP???
2007 Armada
2013 Hyundai Elantra
1972 MG Midget Vintage project
Unstable electrified three wheeled Bicycle truck

924RACR · Posted: Thu Feb 20, 2020 3:42 am Post subject:

924 and 931 definitely are not the same clutch, splines are most definitely not the same.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

hayeslewis · Joined: 21 Aug 2011 Posts: 74 Location: Alexandria, VA

hmm, wonder if it's a weirdo that fit but failed? The clutch out of the ITB car looks exactly like the one I got in the fresh clutch kit. I guess that also confirms it's a 924 torque tube and a 924 snailshell?
_________________
Hayes Lewis
1979 924 HP
1979 924 ITB/HP???
2007 Armada
2013 Hyundai Elantra
1972 MG Midget Vintage project
Unstable electrified three wheeled Bicycle truck

emoore924 · Joined: 13 Apr 2004 Posts: 2822

IIRC the easiest way to tell is to count splines - 924 na is 19, 931 is 25...

Paul · Posted: Fri Feb 21, 2020 12:09 pm Post subject:

_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

924RACR · Posted: Fri Feb 21, 2020 11:05 pm Post subject:

Agreed, or also measure shaft OD if you have calipers...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype