Guys, I've been told I get poor fuel mileage in my I-6 300 Bronco because I have no overdrive. Since I have the stock C-6 tranny, would it make a real difference to swap into an E40D?. In addition, I want to increase power and hill driving capability as well as speed. Someone tells me a tranny/gear change would make even a greater difference than swapping engines... what do ya think (I am considering swapping into a 351W to correct these problems...)

 

People tell me fuel mileage and performance problems in my I-6 300 carbed, C-6 tranny Bronco can be fixed by switching to overdrive. Is this swap worth it, what mods will it take? thanks...

 

The E4OD will give you an overdrive gear and that will let you cruise on the freeway at a lower engine rpm. Weather or not this saves you any gas depends on what tire size and axle gear ratio you have now and what speed you like to cruise at, as well as if the road is hilly or flat and if you do any towing or not.

With an axle gear change, you are not going to get increased power AND increased highway speed. It's one or the other. Low gears (numerically high - 4.10 for instance) will give you more power and a lower top speed, while high gears (numerically low - 3.08 for instance) will give you more cruising speed and less power.

Swapping from a C6 to an E4OD is going to involve more than just changing the transmissions. The E4OD is electronically controlled and needs the wiring harness and computer to go with it. Swapping to an AOD would be easier as these are not elecronic controlled.

The E4OD and AOD/W have a lower first and second gear than the C6, which would help your acceleration a little in those gears. Your C6 can also be rebuilt using the low gear kit, available from Ford through Summit and others for about $350, and has the same first and second gear ratio as the E4OD.

Another possibility for an overdrive gear is a Gear Vendors or US Gear overdrive unit that goes on the back of the tranny or transfer case, depending application. These units are not cheap though: $2500 plus install and driveline length modification.

Finally, if you're looking at swapping the engine and tranny, you will likely be ahead in the long run if you just sell your truck and buy one that already has the engine and tranny combo you want, unless you have a real emotional attatchement to or big monetary investment in this particular truck.