I live in the north east.In the winter i like to put smaller tires on my truck since the 40s i have dont do good on snow covered streets with ice the slide bad.someone told me i can put in an over drive unit so that it would change my gearing.lets say im running 35s in the winter with the stock 4:10 gears yes its fine with a 351w with headers and true duels its automatic i know i know automatic sucks i hear it everyday.but in the summer i want to put my 40s back on and the 4:10 gears dont cut it so i was told i can put an over drive unit in and leave it locked in for the summer and it would change my gear ratio to 5:13's i think?and then ill have no problem for the summer with my 40 inch ground hawgs.but im not sure if these over drive units can handle daily driving all summer like that?...I have no clue what over dirve units are for price i saw a used one on e bay out of a f 350 for $800.why would a f 350 have one in it?maybe for a dump truck?...I really dont know much about over drive units this is the first i ever hear of them..what do you think?...i KNOW IF I PUT an over drive unit in my drive shafts will have to be cut shorter and the othere one made longer..I hope i made it clear what i mean..any info will help thanks...

 

There's the gear vendors over drive unit, I've heard a lot of good things, but I don't have any personal experience with it...

Big trucks use it to get better mileage on the highway (usually with the 3 speed automatics that don't already have OD)

 

There is a few options you have.
You can switch transmissions such as a ZF 5 speed or NV4500 conversion.
You also can add a overdrive unit such as gear vendors, if you want to retain stock tranny. Avvance adapter also offers a range box to mount in front of a Np435 4 speed.
Pretty much anything that involves buying a unit will cost you around $1500 for the unit give or take some.
It all depends on what you want to do and your budget

NIck

 

The gear vendors over drive unit
or
a ZF 5 speed

 

ok so your saying if i convert the truck into a 5 speed shift with a zf 5 speed i will have plenty of power running 40" tires and stock 4:10 gears?

 

Depending on how much you take this truck offroad Personally I would switch to like a 4.56 or 4.88 or even 5.13. Because even with a overdrive just by adding 40s and a lift you kissed your milage good bye.

 

If I had an overdrive unit Id regear with taller than what I felt was necessary without it.

IE = I have 4.56s now but if I put in an overdrive unit I wouldnt think twice of 5.13s with 40s (maybe 5.38s) Plenty of off the line and once youre up to speed decent RPMs.

My truck IS bad a$$ others just WANT theirs to be. -Sig worthy!

Im not stuck up....just making a joke. 4.10s and 40s will bring the suck!