c-6 trans swap

[BobB]

i have a 1972 f-100 with a 302 and c-6 trans 3;55 diff iwould like to go to aod trans hope to better my fuel mileage
i read most of the info and it is very helpful i would like to know if doing the swap will help as i get about 10-11
mpg
thanks
Bob B

[Mancar1]

I would do something in that order only if it was something I just had a burning desire to do. If you r thinking on doing it to save $$ by getting better MPG you will never come out ahead $$ wise due to the cost of the upgrade. You will not get a significant increase in MPG.
I am going to put higher gearing in my Dana rear end but not to try for better MPG. I just want a better cruising RPM. I also think overdrive would be kind of nifty, just because it would be.
All this drabble is just my opinion. Keep on trucking

[BobB]

is 10- 12 mpg normal in my 72 f-100 or am i asking too much for better fuel economy i have 302 2 barrel c-6
auto 355 diff i would to hear from other truck owners and what kind of milage other trucks get ?
thanks
Bob B

[Mancar1]

is 10- 12 mpg normal in my 72 f-100 or am i asking too much for better fuel economy i have 302 2 barrel c-6
auto 355 diff i would to hear from other truck owners and what kind of milage other trucks get ?
thanks
Bob B

You will hear a lot of different answers to the MPG ? on here, as we all have our own opinion. That being said, I had a 70s Ford 1/2 ton with your set up some years back and I rebuilt the 302 with a RV cam. all else stock. I averaged 13-14 MPG. That was city/freeway combined. With over drive I would think a 16 MPG may be achieved depending on driving habits and where you r driving. City, country, ect. These trucks where not designed to achieve good MPG. They where meant to be work horses.
Remember, just my opinion. Keep on Trucking, John

[Craigerf100]

If you swapped both Trans and axle gears your mpg gain wouldn't be improved all that much. 16 at best I would guess. Which isn't all that great Considering the cost of both. I had a fairlane with a 289 c4 and 3.11 gears and my mpg sucked still. If it had an aod with those gears it would help a little on the hwy.

I could be wrong. Hopefully someone here with an aod truck can give u a specific answer.

[sargentrs]

My 302/3 spd manual with 3:25 gears got 15 hwy at best. Avg city/hwy about 12-13. Mileage pretty much sukd but I love driving her! The issue is your driving something really heavy with the aerodynamics of a cinder block.

[Craigerf100]

Also u said u have a 2 b carb. If u buy a edelbrock 4b carb it will help your mpg unless u floor it all the time. These carbs
Have a 2 stage set up wear it runs mainly on 2 small barrels until u floor it then it opens the other 2 big barrel. That could help too.

[BobB]

after a lot of pondering i pulled the 3;50 diff and took it to a ring and pinion shop having them change the ratio
to 3:00 hope to gain some m.p.g. later try a different carb it some aftermarket one on it now i will be asking
for what kind of carb to replace it with i will keep up my progress if any one is interested
thanks
Bob B

[Craigerf100]

600 cfm 4b carb for a 302
Generally edelbrock for daily driving and fuel economy.
Holly carb for performance

But if ain't broke don't fix it. If your carb is running pretty don't touch it unless your gear swop doesn't give you all your desired mpg.

3.00:1 gears? Man that's a jump. It might of been your best option though for affordable fuel economy project.
How much would u sell those 3.55 gears for?

Good luck.

[BobB]

i really don't know what they are worth i was going to put them on the shelf didn't think about selling them
i could ask the gear guy what they are worth .
thanks
Bob B

[Mancar1]

i really don't know what they are worth i was going to put them on the shelf didn't think about selling them
i could ask the gear guy what they are worth .
thanks
Bob B

New I would think under $200. (Not labor but just for parts.) Used maybe $75. Just my (I would ask 1/2 the new price.
Keep on Trucking......John

[youngone]

So did the mpg improve with the gear change?

[BobB]

i can't say here in michigan the weather has been nasty have the new diff installed waiting for better weather
BobB

[tyn2danet]

We are in the process of swapping the C6 out of a 68 F100 for the Performance Automatic Street Smart AOD.

Of course the C6 went belly up so I had to sink some money in to the thing anyway.

The differential is a 3.55 open, but that may get swapped out too. If it ends up with 11-12 mpg, I will be happy. Right now it is running about 8...

[JTW_Jr]

My 390 with rv cam , 670 Holley, Sanderson headers, c6 and 3:55 gets about 8 mpg.

I bought it to drive a good bit, but the gas mpg is killing me !