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Canadian Poncho Homepage -> Canadian Poncho -> 65-70 Full Size Power Train Tech Forum -> 12 bolt ratios. Availability question.
Post Info TOPIC: 12 bolt ratios. Availability question.
cdnpont


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12 bolt ratios. Availability question.
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Was there ever such a thing as a 3.23 ring and pinion for a 8.875" 12 bolt?

 

The reason I ask, is in my thinking, it would be a great on road compromise ratio for a big car with a M20. And I'll be building a 4 leg 12 bolt for my 65 and already have an good open 3.08 carrier.

My current 10 bolt has a 3.36 since it was a six/PG car, but I'm thinking that might be just a wee bit too low out on the open road. And the 3.07 or .08 might be just a little too high making the car a dog in the city, and be hard on the clutch.

Maybe 3.07-.08 would be perfect after all? Maybe I'm splitting hairs?

 

Any thoughts?

 

2.92  = 2239 RPM @ 60mph. 27" tire.

3.08  = 2361

3.23  = 2476

3.36  = 2576

3.55  = 2722



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
ARCADIAN


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Mark I had a 3:08 gear set in my 10 bolt, 327 Chevelle with 28" rear tire and it was a "dog" in town and hard on the clutch (had to ride it). Changed to 3:73 and what a difference! About 2600 rpm at 50 mph. The 3:36 ratio with a 27" tire should be a nice in town and highway setup. My thoughts.
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Chris

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4SPEED427


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Available 12 bolt car ratios as far as I've ever seen--- 2.29 2.56 2.73 3.07 3.31 3.55 3.73 4.10 4.56  and possibly more as dealer installed gears.  I believe the aftermarket makes 3.42 for 12 bolts and didn't know that 3.23 is also available.

225-70-14 tires on my car with 3.07 gears is ok with a 427. I drove it with the same combo with the 283 and it was ok but sure won't win any races. It's at 2550 @ 60mph. I wouldn't want 3.31 or lower gears because I already wish I could put it in 5th on the highway!

With a 4 speed there is no ideal combination between city and highway. You can't have stop light performance and low rpm on the highway, that option just isn't there. For me, the 3.07 is the best combo.



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
65Camino


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Ive got a 3.31 in my Caminos 12 bolt. Cruises nicely in OD.

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66 Grande guy


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Yeah to me 3:31 with an OD and stock height tires is an awesome setup for all round use.  

 



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ken from northern Alberta

38 Willys pickup electric

39 Buick (327 with 700 r4)

66 Beaumont 4 door hardtop

69 Chevy CST pickup

1976 GMC 23'  motorhome

1994 Impala SS 

1968 Citroen Fourgonnette (Yeah Carl!)
cdnpont


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Guys. you're missing the idea of the original question. No overdrive.



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
4SPEED427


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What is the majority of your driving Mark? Stop and go in the city or out on the highway wanting to drive 70 mph?

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
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Prefectca


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I knew of a 68 Beaumont with a 396 that the owner swapped in 3:08 gears and pulled the m20 and installed a 3 ring Saginaw four speed. The three ring had a low ratio for first to give some performance in the city and the rear gear ratio was friendly on the highway. I know that the Saginaw isnt as durable as the Muncie but would be okay as long as you dont abuse it.
Paul

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4SPEED427


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I don't know my Saginaws very well, what do they use for a 1st gear in the one he installed? Seems to me I once heard Vega Saginaws had something like a 3.11 first gear?

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
Prefectca


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The three ring input shaft Saginaw is 3:50 low gear. I found a gear ratio chart.


m.roadkillcustoms.com/transmission-gear-ratio-chart/amp/

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4SPEED427


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Wow, we're talking gravel truck gears here! Look at the spread on those Saginaws.

On one of them, 2nd gear is similar to an M20 1st gear and the other one, 2nd gear is identical to a Muncie M21..

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
66 Grande guy


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cdnpont wrote:

Guys. you're missing the idea of the original question. No overdrive.

 Sorry got carried away with my enthusiam!



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ken from northern Alberta

38 Willys pickup electric

39 Buick (327 with 700 r4)

66 Beaumont 4 door hardtop

69 Chevy CST pickup

1976 GMC 23'  motorhome

1994 Impala SS 

1968 Citroen Fourgonnette (Yeah Carl!)
Nov 18 to Dec 2 Black Friday UP TO 50% OFF Plus Huge Coupons
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cdnpont


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Ken, you'd need a 5 speed to get happy



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
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