I am thinking about changing my gear ratio. I have a 4 speed manual with granny gear in a 77 f150 with a 400 and dana 44s with a 3.50 ratio right now. I very rarely pull anything with it and want a little better gas mileage. Do you guys know how exactly I change my gear ratio so first through third gears are taller and fourth is a bit shorter? And what gear ratio you might suggest.

 

Are you saying your truck has front and rear Dana 44s? That's weird.

In terms of transmission options, tell us whether you have a married or divorced T-case. What model T-case?

 

Just buy another set of taller tires. Also fuel milelage is not an option on these old engines. Its the nature of the beast, live with it or buy something different.

 

If all you wanted was to change final ratios, you change that in the diffferential. Trying to change the individual gear ratios you are describing will require redoing the transmission.

 

Do you know what 4 speed trans you have?


The T18 and NP435 may have optional gear ratios but 4 gear is 1:1


You may want to consider changing to a 5 speed or changing your axle gear ratios. A 5 speed trans (ZF5 is the easiest) would give you the best of both worlds.

 

Going down the wrong path for serious mpg improvement and money savings. You will likely never get your money back out of the cost of the gears, unless you do a lot of driving and set the gears up yourself.

Even going from 3:50 to 3:00ish gears is only a 0.86 gear reduction. For comparison, an overdrive transmission for a truck is usually a 0.75 gear reduction equivalent.

If you do the gear swap, 4th gear is going to be a dog. Unless you live in flatlandia, you may regret the gear change as now you have to downshift into 3rd and wind the hell out of the motor to get up a slight grade hill on the highway.

 

it's the np435 and changing the axle ratios is what I was asking about. I'm not opposed to changing a tranny it's probably quite a bit more expensive

 

Swaping in a used ZF5 may actually be cheeper than changing the gears in the front and rear ends. A trans swap doesn't really require a lot of specilzed tools where as changing gears does and requires precise gear setup to obtain the correct contact pattern and backlash.

So... unless you have done gears before or you really want to learn and are willing to purchase the tools to do so you should add in the labor cost to changing the them. My guess is you'll be into it 1500-2000 to change both axles gears out with new gears. This would leave you with still a 4 speed, no syncro first, non OD trans.


These are all just things to consider.


Your statement of "taller first through third and shorter 4 gear ratio" is only acievable with a new transmission.