Cadillac Owners Forum banner

1 - 18 of 18 Posts

·
Registered
1979 Sedan Deville
Joined
·
465 Posts
Discussion Starter #1
The fluid in mine hadn't been changed since 2001, and it was wet and caked with dirt that stuck to the leaked oil. I ordered a gasket from Rock Auto, the Fel-Pro RDS-550281 that they list. I went to put it on, but it was too small. Double checked Rock Auto, and all the gaskets they list are for the 8.5" or 8.2" ring gear. 1977-81 has an 8.75" ring gear. They don't list a single gasket for that size for 1977-81 Cadillacs! Same problem with all of the local auto parts stores I tried! Finally I used a search engine and searched for "8.75 10 bolt gasket" and finally found the Fel-Pro RDS-30031, which fits perfectly, but is only listed for Buicks, Oldsmobiles, Chevrolets (including some C-10 trucks), and GMCs. Why do all the parts suppliers have it wrong?

I did call a GM dealer parts department, who gave me the discontinued OEM part number of 9778192, which Rock Auto even mentions on the info screen for the RDS-30031!
 

·
Registered
2005 Base CTS work at Pullen solenoids Glass Factory for 36 and a half years
Joined
·
263 Posts

·
Registered
1979 Sedan Deville
Joined
·
465 Posts
Discussion Starter #3
Yeah, they do list that Mahle one. I guess the 8.875" ones are for the limos and commercial chassis, but what would the 8.5" ring gear gaskets be for? And why don't they list the correct FelPro gasket that looks like that Mahle one?
 

·
Registered
2005 Base CTS work at Pullen solenoids Glass Factory for 36 and a half years
Joined
·
263 Posts
You can't expect them to carry every part from every manufacturer in the world can you?

Roy
 

·
Registered
2005 Base CTS work at Pullen solenoids Glass Factory for 36 and a half years
Joined
·
263 Posts
Weren't all 8.875 ring gears 12 bolt only?

Roy
 

·
Registered
1979 Sedan Deville
Joined
·
465 Posts
Discussion Starter #7
It looks like the 8.875 may be 12 bolt only. Ours are 8.75 with 10 bolts on the cover, but 12 on the carrier if I'm not mistaken.

I don't expect them to carry every part by every manufacturer. However, they carry the RDS-30031, they just don't list it for our cars, and the Mahle one is confusing because it doesn't say what ring gear size it's for, and I saw another one that same shape that said it was for an 8.2" 10 bolt.
 

·
Registered
1979 Sedan Deville
Joined
·
465 Posts
Discussion Starter #10
No. The 77-81 Cadillac axles with V8 are 12 bolt guts in a 10 bolt case.
But TA Coupe is talking about 8.875" ring gears. Regular 77-81 Cadillacs have an 8.75" ring gear. Did they ever put a 8.875" ring gear on a 12 bolt carrier in a 10 bolt case, or was it only the 8.75" ring gear?
 

·
Registered
1979 Sedan Deville
Joined
·
465 Posts
Discussion Starter #12
ALL 77-81 are 8.875 in full size caddies.
My FSM says 8.75" for C bodies, and 8.5" for Seville. It says limo/comm has a larger ring gear, but I don't see the size specified, so I'm just assuming that would be 8.875".
 

·
Registered
1980 FBC
Joined
·
3,162 Posts
I've seen manuals call out the 8.875 ring gear as an 8.75 or 8-3/4 gearset.

Dunno where it came from but drmenard is correct.
 

·
Registered
1980 FBC
Joined
·
3,162 Posts
I've been wrong before but I remember 8.875 parts numbers being identical to 8-3/4" gearset numbers.

I believe I found that in a Motor's Parts And Time Guide.
 
1 - 18 of 18 Posts
Top