wabash13

I have a '61 with 4.11:1 gears with posi-traction. I want to switch to something higher to improve mileage, reduce RPM's on the highway, etc. I have plenty of power, with a 350 with a dual carb setup, so I'm not really worried about getting going in 1st or 2nd. What suggestions are there for a good gear setup?

steampunk c1

3.08 with wide ratio 4 speed but check if this crown wheel will fit posi.

toms silver 60

If you don't have too much cam duration, you might be satisfied with a 3.36 or even a 3.08. It won't be as much fun to drive for sure...A 3.70 is only 10% different from what you have, and a 3.36 would be double that with regards to rpm/speed. Just do the math and check out the various on line references.
I just switched back from 3.36 to 3.70 after about 20 years, much nicer to drive in town and not all that different on the highway. This is with a lot of cam, 350, tri power and close ratio Muncie.

1snake

I just went from 4.11's to 3.70's and they are perfect. I have a 283 and a close ratio 4 speed. If I had a wide ratio trans. or more torque I would have gone with 3.55's.

Jim

Audiophobe

In about 2 weeks I will have 3.55's swapped in for my current 4.11's in my 58 245HP 4sp. 60mph right now has me at 3400rpm +/-.
I wanted streetability without raging down the highway so I hope I chose right. I'll report back.

1snake

60 MPH at 3400 RPM's? Either your tach. or speedo is inaccurate. With 4.11's, mine was 60 MPH at 3000 RPM verified with GPS.

Jim

Audiophobe

Maybe 3200, I don't remember for sure but it's definitely no less than 3200. BTW, the GPS only verifies your mph. Maybe your tach is off! Just joking. I'm sure my tach or speedo might be off a bit.

1snake

That's the trouble with a tach. driven off the generator. An in-correct pulley or a slipping belt will affect your readings.

Jim

toms silver 60

ROAD TESTS MAGAZINES
CALC
RATIO TIRES MPH krpm
4.11 6.70 x 15 19.6
3.7 7.75x15 21.3
3.55 6.70x 15 22.5
3.36 6.70x 15 23.5
per 1000 rpm, so a 4.11 should be doing about 3060 rpm.

Redbird

Where is the chart for plugging in those figures? I just saw it somewhere and can't remember where.

PG99

If any of you guys that are swapping out the 4.11's and want to sell the whole case and gears I am very interested.

Please pm me.

PG

wabash13

Let me know what you think once you have them in. Thanks.

Audiophobe

What are you multiplying to get 3060? I'm trying to figure out what I'll get with the 3.55's. Also, where do the tranny ratio's figure in that many posters have mentioned? In any event, that's probably about right. My tach needle has "the shakes" so it could be about 3100 vs 3200.

That's something I am agonizing about. I have an original "P" case 4.11 and on one hand I (but especially my wife) would prefer not to store it and I can't think of a reason to ever put it back in. On the other hand it's nice to have if I ever want to sell it although I'm not sure how much it would matter. It's the same thing with the seats. I just ordered AK customs and will have to store the old seats or sell them.

toms silver 60

Those figures were from old road test results with stock tires. Keep in mind those are with factory size tires. Your speedo and tach relationship should be exactly the same, although your actual speed will change with newer tire sizes accordingly. GPS works great for checking odometer and speed.
Now, magazine reported a 3.55 will go 22.5 mph at 1000 rpm (with 1:1 final ratio). 60/22.5 = 2.666, so 1000X2.666 = 2660 rpm at 60 indicated mph.
Do a query for gear ratio calculator and some threads should show up with several links for mph/rpm.
If your generator has ever been worked on, there is a chance it might have the wrong pulley. It should be ~ 3-3/8". I found out I had the wrong pulley (3") after 30 years, tach was 10% overstating. My old 283 would rev to 8k, or so I thought......It was only about 7200....
There are some limitations with speedo driven plastic gears and transmission driving gears, so you may have challenges getting an accurate indicated mph after the swap.

capevettes

I'm running 3:08's in my 61 with a 383 and a 4 speed. Pulls fine down low and is a great highway cruiser. 70 mph is about 2,500 RPM's

INMYBLOOD

If you just plan to cruise or drive the car around I would think any of those low gear sets would work. Although I hear some complain about taking off from a stop with tall gears. My plan to lower RPMs will be a 5 speed. I've tried 3.03,3.36, 3.55, 3.70. The 3.08 and 3.36 only when my 3.70's broke. I have 3.55's now and I like the compromise, but now with a blown motor torque and hp is a non issue.

billsc1

Just swapped my 4.11 for a 3.08. WAY better at highway speeds but a requires a little more clutch and is a bit lazy off the line with a 2.20 1st gear. Just ordered a 5 speed from Keisler which should improve driveability at both ends.

toms silver 60

A bit lazy? 3.08X 2.20 is only 6.8:1 first gear, preferred first gear should be ~9-10:1. That must really suck starting going up hill at a traffic light or in town compared to the 4.11. It should do much better in the snow, however....The five speed should be a welcome upgrade if you do much highway driving.

billsc1

Dosen't snow much here in Atlanta so I'm not sure what your point is, although you do have an uncanny grasp of the incredibly obvious. BTW as long as you are putting up specific numbers 3.08 x 2.20 is 6.77 not 6.8 (just sayin').

1snake

BUT, he doesn't have to shift into second until he's on the freeway.

Jim