Gear choice
- Thread starter Cottonmouth45
- Start date
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Icetech
Well-Known Member
I believe the OD ratio on that trans is .67.... i personally would go 3.91 or 4.10s... Can always use a RPM calculator to figure out your driving rpms.. I run 4.30s without a OD right now.
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Spicer Engine RPM Calculator
Measure your engine’s RPM based on the ring gear and pinion gear ratio, speed, and tire height, with the Spicer Engine RPM Calculator.
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Cottonmouth45
Member
215/70 14
Icetech
Well-Known Member
3.23 or 3.55.. you are going to have zero traction no matter what..
Cottonmouth45
Member
Just want to have a good time with out redlining it at normal driving around town.
Cottonmouth45
Member
I figured that. Can’t get a wider tire in there unless a get some custom rims made. The rear end is out of a 1976 Aspen station wagon and it was about a half an inch wider than the 7 1/4. I took out. There’s just enough room for those tires in there without scraping on the fender well. I can’t even get one finger in between the tire and the fender well
Cottonmouth45
Member
I can not do a burn out to save my life right now. It’s like driving a tractor. I rarely use 3rd gear let alone the overdrive.The size wouldn't be too bad if you can find sticky tires, not sure if they make anything for 14s though.. Car would be great at burnouts
Cottonmouth45
Member
I was gonna run 3.73 but started thinking that was too much.
Icetech
Well-Known Member
Yeah.. the 2.72 is great if you are on the highway all day
Go 3.73 and be happy... you can always get some 15" rims and stickier tires if you need to. Or cut the wheel opens and make a fake hemi dart
moparlvr166
Well-Known Member
Go with 3.91 and you can drive on freeway in 3rd gear and still accelerate if needed, if you used 4th for OD you would be just below your 2.72 for gas mileage if you want to take a longer road trip.
You are locked in with your transmission and the OD helps.
You are kinda locked in with your exhaust, heads, compression ratio and cam.
You are less locked in with carb and intake manifold.
Build everything based off the cam. You pick your cam based on the performance you want from the engine. That is the computer program that determines everything else.
If you're unwilling to change your cam, then you need to figure out your torque curve and build your gearing around that and how well the heads feed in the air and fuel... You can't complain when you don't get what you really want.
Go on Amazon and look for the Automotive Engine Math book. I'm a retard and i am grateful that book exists.
You are kinda locked in with your exhaust, heads, compression ratio and cam.
You are less locked in with carb and intake manifold.
Build everything based off the cam. You pick your cam based on the performance you want from the engine. That is the computer program that determines everything else.
If you're unwilling to change your cam, then you need to figure out your torque curve and build your gearing around that and how well the heads feed in the air and fuel... You can't complain when you don't get what you really want.
Go on Amazon and look for the Automotive Engine Math book. I'm a retard and i am grateful that book exists.
I would consider a 3.91 to be the absolute lowest numerical gear I would run with the OD and probably more like a 4.10.
with the 3.09 1st those 3.91's will make the car near undriveable.
i just went thru this with a lighter car and shorter tires. immediately needed to change the carb out because it would absolutely boil the tires and then be gasping for air before falling flat on its face getting across a wide intersection.
2nd and 3rd were acceptable though and cruised nice in that 40mph range.
but that's no way to go thru life.
i've ran 3.55's with the 3.09 and that would be the deepest i'd consider.
i just went thru this with a lighter car and shorter tires. immediately needed to change the carb out because it would absolutely boil the tires and then be gasping for air before falling flat on its face getting across a wide intersection.
2nd and 3rd were acceptable though and cruised nice in that 40mph range.
but that's no way to go thru life.
i've ran 3.55's with the 3.09 and that would be the deepest i'd consider.
1WildRT
Well-Known Member
When I typed this and when I edited it there was spaces making things more readable.... But when posted it's kinda a mess....
a833 O/D ratio's are. 1st 3.09 2nd 1.67 3rd 1.00 4th .72
Tire height 25.9"
If you use 3.91's 2500 rpm =
1st 16mph
2nd. 30mph
3rd 49mph
4th 68.5mph
If you use 3.73's
1st 18mph
2nd 31mph
3rd. 51.5mph
4th. 72mph
If you use 3.55's
1st. 17.5mph
2nd. 32.5mph
3rd 54mph
4th 75mph
If you use 3.23's
1st 19mph
2nd. 36mph
3rd 60mph
4th. 83mph
With your current 2.72's
1st 23mph
2nd 42.5mph
3rd. 71mph
4th 98mph
a833 O/D ratio's are. 1st 3.09 2nd 1.67 3rd 1.00 4th .72
Tire height 25.9"
If you use 3.91's 2500 rpm =
1st 16mph
2nd. 30mph
3rd 49mph
4th 68.5mph
If you use 3.73's
1st 18mph
2nd 31mph
3rd. 51.5mph
4th. 72mph
If you use 3.55's
1st. 17.5mph
2nd. 32.5mph
3rd 54mph
4th 75mph
If you use 3.23's
1st 19mph
2nd. 36mph
3rd 60mph
4th. 83mph
With your current 2.72's
1st 23mph
2nd 42.5mph
3rd. 71mph
4th 98mph
I did this math for my 66. I figure with the OD trans and 26.5" tires, I want 3.23 gears. That eases the first gear jump start and still puts me at about 2200 RPM at 70-75 MPH.
33IMP
Well-Known Member
3.23s are an excellent compromise gear for a 1 to 1 high gear trans
With your overdrive, I'd split the rpm difference between 3.23 in 3rd and 3.23 in od.
That way you have lots more gear in the first three gears, compared to a 3.23, and still have less rpm on the freeway in overdrive.
The gear that fits that description is 3.73
I'm assuming an 8 1/4 rear?
With your overdrive, I'd split the rpm difference between 3.23 in 3rd and 3.23 in od.
That way you have lots more gear in the first three gears, compared to a 3.23, and still have less rpm on the freeway in overdrive.
The gear that fits that description is 3.73
I'm assuming an 8 1/4 rear?
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