View Full Version : Taller Gears for Better MPG?
08-01-2011, 05:10 PM
So I'm thinking about swapping out the rear end in my 94 F150 for better MPG's. Currently has the 3.55 (Standard for the Northland Edition F150) And I'm getting 13mpg out of it. Has a 5.0 and is running new plugs, wires and air filter. Cap and rotor apeared fine.
Whats my best bet to get the most mpgs? Has any one done this? Were can I get the gears?
08-01-2011, 11:54 PM
my vote is electric fan, synthetic lube for eng, trans, and rear diff. if it is time for tires you could go with a taller tire and effectively raise the gear ratio. the problem is that the 302 is "weak" and "raising" the gear ratio would not leave you happy with either performance or mileage. i have no personnal experience with but a friend said when he added fuel catalyst (Fitch) he gained on average 1.5 mpg increase. and possibly try e3 plugs which i have personnal experience with (gained on avg 0.8 mpg). other than that good alignment and properly inflated tires. speaking of a hi dollar tire (michelin) can increase mpg. just not the aggressive style.
08-02-2011, 12:00 AM
Don't use the E3 plugs. My buddy put them in one of his vehicles and the plugs pretty much exploded into the cylinders.
08-02-2011, 07:07 AM
You have to match your cruise RPM to the camshaft. Lowering RPM at cruise doesn't mean you will gain MPG. In fact it might make it worse. According to my cam grinder, my truck will get it's best mileage at 2200RPM at 65MPH. That works fine for me as it's a solid roller and it has to stay above 2000RPM.
08-02-2011, 09:48 AM
I hate the 3.31's in my truck, with a 32" tire it runs 2k rpm @ 75mph.
If I run stockish donuts on it I do gain an instant 3-4 mpg with a lot less downshifting on hills.
I do suppose if you use gearing rather than tire size you will come out ahead though, less mass to spin and less contact with the road. Through the summer I threw my old 16's back on it to get better milage.
08-02-2011, 01:01 PM
I bought a 94 E150 Leisure van with a bad R/a. I replaced the 3:55 with a 2:73. It had an E4OD ..351 Windsor. With properly inflated street radials i could get 21.5 mpg. @ captains chairs queen bed, tv, 500lbs of off grid batteries, solar etc.
I DID find however that setting the cruise at a max of 55-60mph was the best performance/mpg...I just returned from a trip as shown in the included pic...
of course and e150 is a little more aero-dynamic i would guess...
I ordered my gearing from Randy's Ring and Pinion...and had a local 4x4 gear shop do the install
i just checked on the website today..they only seem to list a 3:08 as tallest..maybe a phone call would be needed if you want to go taller..
08-02-2011, 01:53 PM
As usual, you're going to get different suggestions on this subject. You really need a tachometer so you'll know what the engine rpm is at 60mph on a "level" highway, and a vacuum gauge mounted where it's easy to see. What is the diameter of the tires on the truck now? This info will help to give you a better answer. (Sometimes gearing up will help...I changed from 3.45 gears to 2.94 gears...HURT my mpg's--I should have gone to 3.08 or 3.18 gears to keep from lugging the engine down---causing the vacuum to drop from 18hg down to 15 hg...).
I realize the above info is more on the "detailed side", but it lets you know exactly what's making the difference in your mpg's.
The info the other members gave you is good info...You just need to give us the stuff I asked for to make sure you don't over-do anything
08-02-2011, 09:57 PM
I'm currently running Bridgestone Baja Wide Tracks 235/75/15 (came w/ the truck and they're basically new @ 9/32) and at 60mph I'm running 2400K and 1600K @ 45mph (only know that cause thats the speed limit on the way to work)
I dont have a vacum gauge :dunno:
I think I'm going to replace the plug wires w/ Accel SS wires and Bosch Platnium +2 plugs. But I'd really like to see at LEAST 16mpg out of it. I'm not holding my breath for 20+ but 16 seems reasonable.
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