I HAVE A 78 F150 W/302 AUTO. 1406 EDEL(CAL.LEAN),
CAST IRON 4BBL, TRI-Y HEADRS, STOCK ROLLERMOTOR,
STKRLLRCAM(211 DUR/.444" LIFT),3.50 REAR W/30"
TIRES. MOTOR TURNS 2,600 @60MPH. I HAD A 3.00"
GEAR BUT SWAP 3RDMEMBER TO GET POSI. I'M AVERAGING
12 MPG CITY/(LITTLE HWY) DRIVING W/A.C. RUNNING.
SHOULD I GO WITH A LITTLE TALLER TIRE, SWAP
IN A GEAR, MAYBE A DIFFERENT TYPE CAM, OR
HUNT DOWN A AOD TO REPLACE THE C-6. ANY HELP
OR FEEDBACK IS APPRECIATED. THANKS

 

I have a '77 F-150 with 400 cid motor and I get about 12 MPG. My truck is bone stock, 31" tires. I don't however run the AC, because I don't have.
My thoughts on tranny/overdrive swaps -
I spend about $1000 a year on gas ( roughly $20 a week ). A tranny swap will cost at least $500 and may improve my mileage 5-10% or $50-100 a year. It will take at least 5 to 10 years to break even. Not worth my effort. Same goes for fuel injection.

 

Based upon what you posted, you would be turning some 2350 rpms at 60 mph with a manual; you have a 10% auto trans slippage. Not bad but could be a little better. Going to 33 inch tires would drop your 60 mph rpms about 200 rpm. You should target the rpms for the low 2000. Suggestions: Get out the vacuum gauge and time the engine for a max reading (without pinging) and try it. Mount that vacuum gauge on the dash and see if your driving habits can be improved. When you need new tires, consider larger ones. Normally I would suggest an RV cam but from what I have, a stock 302 has a very flat torque curve from 2000 to 3000 rpm and even 3500. That really can't be improved upon so work on the rest of the drive train.

 

AT 60MPH IT TURN 2,600 , AT 70MPH IT TURNS 3,000.
I JUST PICKED UP A DANA 60 WITH A FACTORY 2.72
FOR FREE FROM A FRIEND OUT OF ANOTHER 78. I WAS
THINKING OF SWAPING IT IN AND TRYING IT OUT
AND DETERMINING WHAT GEAR/TIRE COMBO I CAN GET.
BUT BEFORE THAT I AM GOING TO SWAP MY 30" TIRE
FOR SOME 32" INCHER THAT ARE ON MY DAD'S 4X4.

 

The mpg is about right for that setup. That big Ford iron loves gas. The rear change will be a big help. Going up in tire size and going down in rear numbers has the same results. You will reach a point when you cross the line, and you lose power, so keep your eyes open and enjoy.

John

 

One other thing. If you are mainly drivng in the city at speeds of 40 - 50 mph, forget about an AOD. AODs kick in around 40 to 45 so at any speed under that and you might as well have the 1:1 of the C-6. Other than overheating, nothing will kill an AOD faster than the trans hunting back and forth from 3rd to OD on city streets. Under 50 mph, you should keep an AOD in 3rd. Just have the C-6 rebuilt when it becomes necessary.