1964 Buick Riviera ST400 kickdown case connector o-ring

[RiVin]

My transmission's last leak is the case connector o-ring.  I've looked all over for the o-ring with no luck.  Can anybody give me a source or even a good part number might help.  This is a 1 year only part.  The case connector is a small diameter compared to the 65 & 66, thus taking a smaller o-ring.  I can find them for the 65 - 66, but not for the 64.  The reason they got bigger for 65 was because the switch pitch & the kickdown went through the same connector.  No switch pitch in the 64. Help! Thanks

[joe_padavano]

Just match up the old o-ring at a hardware store or Tractor Supply. The cross section is more important than matching the exact diameter. Silicone is your best bet for chemical resistance, but viton will work.

[joe_padavano]

I'll add that early Caddy TH400s also use this small connector and Fatsco has the correct o-rings for them.

[RiVin]

Okay folks. I just successfully resealed my leaking ST400 downshift case connector with a correct SAE size O-ring. It is a 9/16" x 3/8" x 3/32".  That is 9/16 OD x 3/8 ID x 3/32 cross sectional diameter.  It is readily available at your local NAPA store for 50 cents each.  Very important! This is a one year only case connector O-ring for 1964. In 1965 they combined the switch pitch connector in with the downshift connector and the whole connector became much larger in diameter. Best!