can gears improve gas mileage and acceleration?

[bnickel]

An I the only guy that loves the sound of my engine at 3500rpms? If you get decent heads, a lumy cam and decent exhaust, it's music to my ears.

i do love the sound, but you know sometimes when you've been on the road for a while the drone kind of makes your ears hurt.

 

[ultrastang]

Am I the only guy that loves the sound of my engine at 3500rpms? If you get decent heads, a lumy cam and decent exhaust, it's music to my ears.

One of the first things I did, in 1982 after I bought my '68 at age 16, was to dual it out with glass-packs. At first, the blarring sound was cool, but after about about a year of listing to it, I ditched them for turbo mufflers and that's all I've had since.

I like a nice rumble, but loud is annoying if you're traveling more than 30 miles, or if the car is your daily transportation, which my '68 was for 7 consecutive years.


www.ultrastang.com

 

[bad68coupe]

If you are running a C-4, C-6 automatic, or Top-Loader 3- or 4-speed manual transmission (all 1:1 in high gear), then you are greatly limiting the capability your car has in both performance and economy.

The best choice is to run a lower gear ~3.25-3.70:1 in conjunction with an overdrive transmission, such as an AOD or T-5 manual 5-speed (typically .68:1 in overdrive).

The overdrive will allow you to take advantage of off-the-line acceleration with a lower rear end gear, but at cruising speeds, the engine RPMs will drop drastically once the transmisssion goes into overdrive.

As an example, if you had a 26" tall tire, 3.00:1 rear end ratio, and non-overdriven transmission, your engine RPMs at 60 MPH would be ~2,326 RPMs. Given this very same senario, except coupled to an overdrive transmission, your cruising RPMs at 60 MPH would be 1,582 RPMs --744 RPM drop.

A T-5, in overdrive, coupled to a 3.50:1 rear end ratio would cause the engine to "see" the rear end ratio as being 2.38:1 (3.50 x .68 = 2.38:1). Even though the rear ratio may be 3.50:1, in overdrive, the engine thinks the rear ratio is 2.38:1 --That's even higher than a stock 3.00:1 ratio with no overdrive, so you would actually get better mileage with the 3.50s over the 3.00:1s, and still have much more accelleration in 1st - 4th gears with a T-5, or 1st - 3rd with an AOD.

http://www.ultrastang.com/Rearinfo.asp?Page_ID=3

I already rebuilt my C4 so i am stuck with it for a while

 

[bad68coupe]

All diffs are third members. There are diffs with integral carriers, and diffs with removable carriers. It takes special tools and a knowledge of how to set gear patterns. It's not for a novice.

What gears do you have now? I am willing to bet that they are real close to 3:00 to 1.

I have changed out gears before on the kind of rear end where there is an inspection plate, but not like the one on my 68. i didn't think it was that difficult, a little time consuming but not to hard. so how hard is it to change my stangs compared to the other style?

I am not sure what gears i have right now, it is a stock 68 rear end. i will check the tag later and post it.

 

[Max Power]

If it is a stock rearend, you may already have 3.00:1 gears. They were very common.

 

[doug68hoss]

just get another third member with gears close to what you want...

 

[ultrastang]

I have changed out gears before on the kind of rear end where there is an inspection plate, but not like the one on my 68. i didn't think it was that difficult, a little time consuming but not to hard. so how hard is it to change my stangs compared to the other style?

I am not sure what gears i have right now, it is a stock 68 rear end. i will check the tag later and post it.

If your '68 came stock with a C4 automatic, it's very likely your ratio will be 2.79:1, just like my '68 was.

http://www.ultrastang.com/Rearinfo.asp?Page_ID=5

 

[bad68coupe]

just get another third member with gears close to what you want...

thats too expensive

 

[70vert]

I can attest to the effect of high gearing - my 35-year-old 302-2v with the original carb and a 2.79 rear with a new TKO600 tranny with a .64 final gear got over 20mpg, probably close to 25mpg, on a recent 200mpg round trip I made. And this was in 90 degree weather.

with a 2.79 rear and the .64 final drive, you just basically fall into 5th gear and lope along on the freeway. Not a bad sensation, actually . . .

 

[Max Power]

thats too expensive

No it isn't.

You can swap in a non-posi 3.00 chunk for probably about $50.

Nobody wants em.

 

[bad68coupe]

No it isn't.

You can swap in a non-posi 3.00 chunk for probably about $50.

Nobody wants em.

really, everything i have seen so far is around $600. where can i get that 3.00