I'm kind of interested. Great value. I have a 12 bolt housing and would like to change it out into my 65 to get rid of the gimpy 3 arm 10 bolt setup.
But how would 3.08's work with a 327/M20 with 27" tall rear tires? The 10 bolt in there is 3.36, which might be optimal for this combo, although I've never seen 3.36 available new today for a 12 bolt. Just 3.42's.
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
I have 3.07's in the back of my Parisienne. They rev a little too high for me (3000 rpm) when I'm cruising down the highway at 80 mph. I'm running P235/70R15's. Your small block might not mind the rev's.
I wouldn't go any higher (numerically lower) than my 3.07's. I've got the torque to get it rolling, but they're a decent compromise as I'd hate to see what I'd be revving with 3.36's.
I'm kind of interested. Great value. I have a 12 bolt housing and would like to change it out into my 65 to get rid of the gimpy 3 arm 10 bolt setup.
But how would 3.08's work with a 327/M20 with 27" tall rear tires? The 10 bolt in there is 3.36, which might be optimal for this combo, although I've never seen 3.36 available new today for a 12 bolt. Just 3.42's.
I ran my car for one summer with the 283/M20 3.31 combination and it was fine Mark. I suspect the 327 torque would make up the difference between the 3.08 and 3.31 ratios. What I'm trying to say is, I bet the 327 would be as good or better with 3.08 vs. the 283 with 3.31's.
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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
There are online calculators to provide rpm with various rear end ratios and tire sizes. You may even be able to borrow a larger or smaller tire to test the effect of a rear end ratio change.
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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic
3.08's would be 2600 at 65 which is probably the minimum highway speed you'd need to not get run over down here. Not too bad for travel. One can see the issue with 3.55's.
I've bought Barry's gearset. And sorry for stringing this out so long Greg.
Now I have a winter project!
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
3.08's would be 2600 at 65 which is probably the minimum highway speed you'd need to not get run over down here. Not too bad for travel. One can see the issue with 3.55's.
I've bought Barry's gearset. And sorry for stringing this out so long Greg.
Now I have a winter project!
I'm thinking you mean a 26.5" tire Mark
That would be a heck of a way to bring down the RPM though...
To get an idea as to the difference between the 3.08 and 3.36, that is a similar rpm drop between the two of them that a lock up torque converter on a TH350 makes. In this case 181 rpm and I think a lockup is typically in the 250-300 rpm range.
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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
I wouldn't go any higher (numerically lower) than my 3.07's. I've got the torque to get it rolling, but they're a decent compromise as I'd hate to see what I'd be revving with 3.36's.
I am thinking about installing a mild 402 BB/4 speed in my 68 Bel Air. I have the choice of Muncie M20 or M21; or a BW T10. I also have a choice of posi rear axle ratios: 3.07; 3.36; or 3.73.
Wondering what you guys think might be the best trans and diff ratio combo for comfortable drive-ability and strong performance.
I ran my car for one summer with the 283/M20 3.31 combination and it was fine Mark. I suspect the 327 torque would make up the difference between the 3.08 and 3.31 ratios. What I'm trying to say is, I bet the 327 would be as good or better with 3.08 vs. the 283 with 3.31's.
Ouch, my time at the lake was obviously real good, I'm running 3.07 with an M20 in my car, NOT 3.31....
And I just came back from a 35 mile trip with my car. The GPS showed 62 mph, tach said 2700, 225/70-14 tire.
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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
I wouldn't go any higher (numerically lower) than my 3.07's. I've got the torque to get it rolling, but they're a decent compromise as I'd hate to see what I'd be revving with 3.36's.
I am thinking about installing a mild 402 BB/4 speed in my 68 Bel Air. I have the choice of Muncie M20 or M21; or a BW T10. I also have a choice of posi rear axle ratios: 3.07; 3.36; or 3.73.
Wondering what you guys think might be the best trans and diff ratio combo for comfortable drive-ability and strong performance.
Go with the wide ratio M20, and 3.07 rear gears. I'm not sure of the tire size on your 68, but if the tires are any shorter than my P235/70R15's you'll be revving over 3000 rpm at 80 mph.
As a side note, I had a bit of a chuckle when Mark did his rpm calculations at 50, 60 & 70 mph. I'm just getting going at those speeds.
How fast do you guys drive these things? I see 80 and some times up to 110 regularly and pretty quick in my 67, but I just kiss that number, then thats it, and back down she goes.
I figure 50 -70 is where most of the continuous running happens, with 55 probably being the comfortable sweet spot on the backroads around here.
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
I wouldn't go any higher (numerically lower) than my 3.07's. I've got the torque to get it rolling, but they're a decent compromise as I'd hate to see what I'd be revving with 3.36's.
I am thinking about installing a mild 402 BB/4 speed in my 68 Bel Air. I have the choice of Muncie M20 or M21; or a BW T10. I also have a choice of posi rear axle ratios: 3.07; 3.36; or 3.73.
Wondering what you guys think might be the best trans and diff ratio combo for comfortable drive-ability and strong performance.
Go with the wide ratio M20, and 3.07 rear gears. I'm not sure of the tire size on your 68, but if the tires are any shorter than my P235/70R15's you'll be revving over 3000 rpm at 80 mph.
As a side note, I had a bit of a chuckle when Mark did his rpm calculations at 50, 60 & 70 mph. I'm just getting going at those speeds.
Thanks for the input. That combo would approximate yours. I'll be running BFG 225-70 15 tires, slightly smaller than the 235, probably ~26.5 inches vs ~27
