has anyone installed a newer 6 speed auto in our older f150's, 1997-2003?? can it be done? what would have to be done with the computer, wiring harness, drive shaft? im looking at MPG savings. the 6 speed autos are slowly getting into the salvage yards and prices are coming down.
is it poseable to get better then 18.2 miles to the gallon with our 5.4 4x4's, that was totally babying it going up north on the state highway going a steady 57mph, in the middle of the night with no other traffic. Normal regular daily driving is 14.5 - 16.5 mpg. i would like to see better daily driving mpg's.. i own a 2003 5.4 4x4 auto

 

You won't get any better gas mileage - the final drive ratio in 6th is almost the same as your old one in 4th. Your mileage is about what you would expect with your truck, if you need better mileage, take the money you would spend to get a swap working and buy a beater 4 cylinder car.

 

Like glc said, the transmission is not a determining factor for MPGs. Weight is the #1 factor, with aerodynamics in close second. Shave a couple hundred pounds, lose the spare tire, tailgate, replace all the glass with lexan, and get rid of all the seats and A/C system and you might see a 1.0-1.5mpg gain. Then lower it and get some low-profile tires with wheels, side mirrors and polish the darn out of it and you might see another mpg.

You own a truck. Trucks are meant for work. They've all been (roughly) getting the same mileage for the past 30 years. Physics cannot be beat when engineers are only extracting 18% of power from liquid unleaded gasoline.

 

To expand on this, you would have to have a way to shift the extra gears.
The stock PCM is not equipped with outputs to those extra transmission solenoids as well the program is not equipped to handle the shift points.
If the trans will fit against the motor and all items and issues are solved, the only possible way would be a stand alone controller.
Finnally, you could not use a later PCM because it is programed and equipped to run a totally different engine setup that the old 4.6/5.4 does not have.
IMHO, the cost of the attempt far out weighs the end result.
The 6 speeds are only an attempt to split up the engine torque into smaller rpm ranges to keep the motor in it torque range more of the time.
The final ratios are nearly the same in the highest gear.
You just cannot keep increasing the gear ratio/lowering the engine rpm because you run out of engine torque to pull the weight.
The results of that would be to move the throttle closer to the floor trying to get the motor to pull the weight, and so the fuel savings goes out the window.
In any given engine design, there is a limit to how much efficiency you can get without changing the engine design and equippage.
Good luck.

 

Oh, I'd be curious to know if you're thoughts have changed now that they're getting 22+

 

Just get the 10 speed

 

They now have different engines.

That's even more complicated and the 10 speeds have issues.

 

I have to laugh... but this is as silly as wanting to put an 18 speed Eaton Fuller behind a 4.2l v6.

I've found that the best way to get great mileage is upkeep, appropriate tires, and responsible driving habits.

 

There is a LOT more to this than just installing MORE speeds.
The major purpose is to keep the engine in it's best Torque range as much of the time as possible.
For example; the 4.6l attains max torque in the 3200 rpm range.
To take advantage of this, the engine control system needs to operate on optimized software and sensors to keep the motor and trans rpm to gear ratio and load within a reasonable range of max average engine torque under the max amount of driving conditions.
There is some advantage to this by maximizing engine fuel mileage and limiting needed throttle opening for power almost never needed to pass more air and fuel needed to support it.
Question is how would you do this with just s trans change.
Some vehicles have 8 speeds in an engineered system and still hardly ever get into top gear in many part of the country but flat lands.
ZF, GM & Ford all have versions of these types and grapple with the software and updating as it is.
Good luck to any who try it with back yard engineering that results in anything worthwhile for results.
Best to use the computer on "your shoulders" and control the foot action..