Best rear-end gear ratio for C6

[BigMike]

I plan to install a C6 in the Spring. Right now the '65 has a 4.10 D44. What gear ratio should the rear end have for the best all around performance. I don't plan to haul stuff and want something suitable for around town driving as well as driving on the highway (like to SS).

Thoughts?

[jkimbrel65]

I run 3.25s behind a 390 c-6 combo in my 62 uni.On a good day I get 13-15 mpg.To ss 04 in Aug I averaged 9-11.

Mike

[Uncle Skip]

Mike.
You're opening up a real can of worms here.
This question is strictly a matter of personal opinion and I'm sure lots of guys will chime in here.
If it were me, I'd swap out the entire rear end to a 9" and find a 3.25 gear set.
It has proved to be pretty much the best compromise I could find. Has plenty of grunt for around town cruising and gets fair gas mileage on the highway.
Personally, when I get to the point of going to Slick Stock next time, I just finished a 2.75 open chunk that I've recently completely rebuilt that I'll swap in for strictly highway use.
My tri-power gets really thirsty when it cracks into the end carburetors.
Just my dos centavos worth.
Uncle Skip

[ronk16]

Uncle skip is right on here, too many variables for a blanket question. I am running a 4.10 locker in a big bearing 9 inch, c6 with a 3200 stall converter behind a 400 with 70 cj 4v heads giant voodoo cam and the works. cant figure out why the gas milage is so bad though........what i am saying is build the tranny to fit the purpose and engine of your ride.

[BigMike]

I need to investigate how the D44 has changed over the years. But there are guys over on my Jeep forums throwing away 3.21 gears for that axle.

[banjopicker66]

I am with US on this one.
I would highly recommend changing the rear axle out to a Ford 9" to have more (and easier swap!) rear gearing options.
I had a 3.50 behind a 352 and a 3-speed OD, and that ratio was just right.
I tried a 3.00, and it was terrible, I had to feather the clutch off a level start!
Now, a 4-speed with a granny low (instead of a 3-speed OD) would have found that just fine, except that on a hill with a heavy load it would have alot of problems.
When my 352 blew up, I put in a 460/C-6, and upped the rear end ratio to 2.75, just as US is suggesting.
With all that power, I can pull a heavy load and still get good highway mileage - if I keep my foot out of it that is!
Mileage around town is terrible, though.
Also, the purpose and use of the truck needs to be taken into account. As I mentioned above, a 4 speed with granny gear can really use a 2.75 or even a 2.50 - but it won't be any good for heavy loads.
Since I do not know what engine/transmission combination you have, I can't really make a good specific suggestion.

[Uncle Skip]

Mike.
IF you can get something in the 3.0 range for your Dana, I think you'll be a lot happier.
Its just that there are so many 9"'s out there and parts are so plentiful that if you can't find the higher ratio, its a cheaper way to go.
If you can get a 3.21 Dana, go for it.
U@ss

[BackyardRest]

I plan to install a C6 in the Spring. Right now the '65 has a 4.10 D44. What gear ratio should the rear end have for the best all around performance. I don't plan to haul stuff and want something suitable for around town driving as well as driving on the highway (like to SS).

Thoughts?

What is the height of your tire?

[Jonas]

I plan to install a C6 in the Spring. Right now the '65 has a 4.10 D44. What gear ratio should the rear end have for the best all around performance. I don't plan to haul stuff and want something suitable for around town driving as well as driving on the highway (like to SS).

Thoughts?

What is the height of your tire?

That is a good question. My F250 with a 4.10 rear end and tall tires, calculates almost equal to my F100 with a 3.50.

[LA 66]

I need to investigate how the D44 has changed over the years. But there are guys over on my Jeep forums throwing away 3.21 gears for that axle.

There is a carrier break at 3.73:1. 3.73 and down vs. 3.90 and up.

The 9" is much easier. Just find the right ratio and spline count at the pick in pull, bring it home and throw it in.

[Michelle]

I have a 3:25 behind the C6 in my 56 F100 and have found that to be a great compromize gear for city and highway. The truck is light on the rear and it is hard to keep from braking loose as it is, even with a locker. With anything lower it would be impossible.

[66camperspecial]

I got 3.54 gears in my 66 F250 and with the little I have driven it before tearing it apart for paint I liked it alot better then the 4.10s it came with,the 3.54s did not inprove the gas mileage with the original 352 but the 460 likes those gears and does not do to bad on gas if I keep my foot out of it.

[64 f100]

Deffinately a 9 inch for several reasons, the main one being an easy gear swap for any occasion. Want to make a road trip then swap in 2.75 or even 2.50 depending. This is the advantage of the 9 inch over the Dana. You can change out the hog head and be back in business at the raio you want in an hour, if you have everything ready and know what your doing.

Rich

[Hoofbeat Racer]

might as well add my 2 bits

I am also running a 31 spline 9" with a locker and 3:25 gears. I have 27" street tires and will run a 28" slick. 600 big block ponies in front of it and it gives me the best of all worlds. Needless to say fuel economy is not a consideration.