Save Gas: Tranny or Rearend?

[ky71truckguy]

A quick question I have a 302 2V with a 3 spd not sure of the rearend ratio but just looking to get ideas on making it more highway worthy. Honesty is always appreciated!

[bluef250]

Might consider installing an overdrive - t85 or other. For highway cruising, installing an overdrive probably provide best return for a mechanical improvement. Been a lot of discussion about using acetone as an additive. Some have reported 2 mpg increase, others nothing. Been thread on both subjects recently.

[flyboy2610]

Change the rearend gears. Final drive on the tranny is 1:1 unless you install the overdrive. That's a lot of money. Your most cost effective solution is to change the rear gears. It's a job where you can do most of the labor yourself. You can pull the pumpkin out and reinstall it yourself. Changing the gears and setting them up right is a job best left to someone with the tools and experience to do the job.

[ky71truckguy]

Thanks! Its a wide open question, but I appreciate the tips

[oldschoolrods]

gears will give you better economy than changing the trans. over drive and gears would be hope that helps.

[spartman]

You could look for a SROD manual tranny.

They were found in FORD trucks from the 80's and as long as you don't need it to be heavy duty it would be another alternative.

[cdherman]

Honda.....

Seriously -- most drive line mods don't pay for themselves. Even 2 mpg better won't pay for a $600 tranny swap. And you will seldom get more than 2-3 mpg improvement, in spite of what you will read sometimes. I suppose the exception is swapping a rear chunk for a lower # ratio rear, especailly if you are high, and/or running small tires.

Painful to hear, I know. But face it, driving a brick is never going to be very fuel efficient.

[jzjames]

Headers and a dual exhaust.
Keep it well tuned up and drive economical. Your s/b could get somewhere around 14-15 mpg.

[steveheer]

I agree!! A well tuned rig will help the most. If you have a VERY low gear with small tires I can see where a gear switch could help.

My F100 got about 13 in town and about 17 on the freeway with 3.50 gears and a 300I6. I now have an overdrive and I can get oh--maybe 17. Ok, it may be slightly better than before but not much!!--now I just drive faster

[ky71truckguy]

Thanks for the tips guys!

[ky71truckguy]

Thanks for the tips; especially from those that were in the exact same situation I was in, much appreciated

[ShortBedF250]

Try Electric Fans!
I have an Explorer 5.0L that used to get 17 to 18 mpg and now gets 19 to 20 just by dumping the belt-driven fan and installing a pair of elect fans. Cost less than $200 for two good size fans, controls and gauges. It also has better throttle response and is much quieter. It works great for cruising in mild climates. However, I'd NOT recommend elect fans for hot desert climates or lots of idling or stop-and-go driving.

I recently did the same thing to my 67 Ford PU that has 300 cu 6 cyl, but I
have not driven it enough yet to calc mpg.

[ToughOldFord]

I gained close to 1mpg by adding a fan clutch. Went from 7mpg to 7-8mpg.

[Jake11]

Yer pushing a brick thru the wind! I get 11mpg downhill with a tailwind.

"Diesel" if you want economy. I look at it this way. My Wife's 150 costs
us around 700 a month in payments and insurence. My old 71 is payed
for. I don't want/or like the new stuff. I got a pretty good fuel allowance.
And my truck has "character" as I call it. The new ones are nice, but if
you took the badges off, you probably could not tell which one you was in.
They all got grey cloth interiors, power seats and windows. And springs
more for "ride nice" than for hauling. I prefer "character". JMO

[occupant]

I think rear end gears make a good difference. Cop package Crown Vics with the 3.27 or 3.55 gears don't do nearly as well for economy as the base models and LXs with 2.73 gears. The best I ever saw in my 1998 Crown Vic taxi (P71, duals, 3.27 open rear) was 20mpg driving 75mph steady state from TX to OK. That cab averaged 17 in mixed driving though. The best I got out of a 1999 Grand Marquis taxi (M74, single exhaust, 2.73 open rear) was 24.5mpg driving from Dallas to Austin and back. It stayed close to 20-21 around town. I also had a 2000 Crown Vic (P71, duals, 3.55 rear) and it got mostly 17mpg and I never took it on a long highway trip but I assume it'd do 19-20.

As for trucks, the 302/auto/3.30:1 '67 I had when I lived in Ohio was ok. Fresh tune and it did 12 in town driving hard and 16 on the road driving easy. The beat to hell '70 I had last summer with a 351W and a 4-speed and 3.50 gears, I didn't drive it enough to really tell. But I do know I didn't do well enough to be getting 15, because my van was getting 15 and I could go farther with it per gallon.

I'm thinking really tall gears will help on the highway, but only if you do a lot of highway driving. For driving in town, with a 302 and a 3-speed with no overdrive, I'd keep the 3.30 or 3.50 gears you probably already have.

Best bet is to get yourself a vacuum gauge, and maybe a tach. The less gas you give it the better. And a vacuum gauge will help you let off after you get up to speed. Try to keep the needle as high as you can while cruising. The vacuum gauge I had in my '67 helped me stay closer to that 16mpg when I paid attention to it. A tiny lift off the gas while cruising, I didn't lose speed, only gained vacuum. And that helped the mileage.