factory gear ratios?

GoldOlds · January 5th, 2008, 12:44 PM

Does anyone know what gear ratios were available for the '69 Cutlass Supreme with TH350 and 4bbl 350? My car has 3.73 gears in a Chev 12 bolt, which I suspect is NOT original (not that I'm complaining).
Thanks!

- GoldOlds

Redog · January 6th, 2008, 07:02 AM

Do you still have the RPO tag in the trunk?

GoldOlds · January 7th, 2008, 10:45 PM

Afraid not. The main reason I suspect the gear ratio is not original is the spedometre/odometre. They're slightly off. But then again, the rear tires (255/60/15) aren't the original size either. The rims LOOK original, but I think the originals were 14", NOT 15".

- GoldOlds

monzaz · January 8th, 2008, 01:02 PM

probably a 12 bolt olds rear was the original or 12 bolt chevy if it was Canadian car.

12 bolt olds 2.56 2.78 3.08 3.23

12 bolt chevy 2.56 2.73 3.08 3.31

Doubt it was anything steeper than that. ONLY the high performance versions of your car would have 3.42 3.73 3.55 3.90 etc.

12 bolt chevy rear look at the passenger axle tube between the spring perch and the center section casting on the front face of the tube.

there should be some letters and numbers stamped into the tube that will tell you the original ratio of that axle housing.... In the cast webbing of the differential you will find the date code the housing was cast also, letters and numbers again BUT cast into the housing NOT stamped.

example B 23 9 (Feb) 23rd 1969 cast housing.

example of axle tube stamping ccw 0230 B

J-(Chicago) · January 8th, 2008, 01:46 PM

those are some pretty meaty tires for a 69 cutlass

GoldOlds · January 8th, 2008, 10:52 PM

Yeah, those tires alone provide more traction than the car actually needs (for now at least). I put the rear end up on jackstands and did the ol' "turn a rear tire one full rotation to see how many times the driveshaft rotated" test. It was roughly 3 3/4 times (although that method, of course, is not an exact science). It IS a Canadian car, with the tell-tale "upside down V" on the diff cover.
Thanks for the input, everyone!

- GoldOlds

January 5th, 2008, 12:44 PM	#1 (permalink)
GoldOlds Senior Member Join Date: May 2007 Location: Chatham-Kent, Ontario Posts: 117	factory gear ratios? Does anyone know what gear ratios were available for the '69 Cutlass Supreme with TH350 and 4bbl 350? My car has 3.73 gears in a Chev 12 bolt, which I suspect is NOT original (not that I'm complaining). Thanks! - GoldOlds

January 6th, 2008, 07:02 AM	#2 (permalink)
Redog Alero Chapter Secretary Join Date: Aug 2006 Location: Newtown, PA Posts: 1,144	Do you still have the RPO tag in the trunk? __________________ Me 2000 Alero running 14's 2005 Nissan Altima (her's) 1967 Olds 330 motor sitting on a stand 1985 Delta 88 w/1968 350 rocket ( MURDERED )

January 8th, 2008, 01:02 PM	#4 (permalink)
monzaz Registered User Join Date: Jul 2006 Location: Richfield, Oh Posts: 204	Ratios probably a 12 bolt olds rear was the original or 12 bolt chevy if it was Canadian car. 12 bolt olds 2.56 2.78 3.08 3.23 12 bolt chevy 2.56 2.73 3.08 3.31 Doubt it was anything steeper than that. ONLY the high performance versions of your car would have 3.42 3.73 3.55 3.90 etc. 12 bolt chevy rear look at the passenger axle tube between the spring perch and the center section casting on the front face of the tube. there should be some letters and numbers stamped into the tube that will tell you the original ratio of that axle housing.... In the cast webbing of the differential you will find the date code the housing was cast also, letters and numbers again BUT cast into the housing NOT stamped. example B 23 9 (Feb) 23rd 1969 cast housing. example of axle tube stamping ccw 0230 B

January 8th, 2008, 01:46 PM	#5 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 2,668	those are some pretty meaty tires for a 69 cutlass __________________ I'd rather have a numbers matching poker hand.

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January 7th, 2008, 10:45 PM	#3 (permalink)
GoldOlds Senior Member Join Date: May 2007 Location: Chatham-Kent, Ontario Posts: 117	Afraid not. The main reason I suspect the gear ratio is not original is the spedometre/odometre. They're slightly off. But then again, the rear tires (255/60/15) aren't the original size either. The rims LOOK original, but I think the originals were 14", NOT 15". - GoldOlds

January 8th, 2008, 10:52 PM	#6 (permalink)
GoldOlds Senior Member Join Date: May 2007 Location: Chatham-Kent, Ontario Posts: 117	Yeah, those tires alone provide more traction than the car actually needs (for now at least). I put the rear end up on jackstands and did the ol' "turn a rear tire one full rotation to see how many times the driveshaft rotated" test. It was roughly 3 3/4 times (although that method, of course, is not an exact science). It IS a Canadian car, with the tell-tale "upside down V" on the diff cover. Thanks for the input, everyone! - GoldOlds

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