Changing gear ratios: opinions/suggestions wanted!!

[BigT]

My 78 K20 4x4 has factory 4:56 gears in it and a TH400 transmission. These are great when off-road or pulling something, but poor on the highway. I grew up with a 75 half ton 4x4 with 3:73 gears and a 4 speed manual, which was very versatile for both off-road and highway, but that was partly due to the 4 speed manual transmission. I'd like to switch out my low gears for something more versatile, but I can't decide on 3:73s or 4:10s, as I don't have an experience with either ratio in combination with the TH400, since I just bought the truck a few weeks ago. I'm leaning toward 4:10s, as I used to have a 74 F150 with something close to that combo, and I liked it. But, the 3:73 is the more common one and gets better mileage, etc. We've touched on this in another thread, but I'd really like some more thoughts from other folks who have experience with either. Thanks!

 

[77Dmax]

A 4l80e with a standalone computer would be pretty slick here, otherwise I would go 4.10s.

 

[PartsMan79]

I would put some 35" tires on with the 4.56 that you have.

 

[BigT]

So tell me more about the tranny swap options - 4L80E or 700R4? Is that less work/cost than swapping gears and carriers?

 

[CountKrunk]

I want to go 4L80e with a standalone.

Anyone use these guys before?

US Shift Stand-Alone Transmission Controllers

US Shift Electronic Transmission Control Systems let you take charge of your 6R80, 4R70W, E4OD, 4R100, 4L60E, or 4L80E transmission and unlock its true potential. Our transmission controllers are compact, packed with features, and have a built-in display for tuning as well as user-friendly...

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[DoubleDingo]

Gear swap would be 3.73. My 81 has 4.10s, and they are fine, but only around town or short runs on the highway where I can keep it around 60-65 tops. Highway, the engine is turning pretty good, more than I'd like while going so slow. 3.73s will drop the rpms down some. You have enough slippage with the TH400, 3.73s would be ideal for what you're doing with it. Yes, 4L80E and no gear change gives you the same gearing down low and overdrive for the highway. It all depends what you want to spend your money on and what you want to modify to get the results you're looking for.