I ended up doing a short arm 3.5 inch with a few drive train components. The axle ratio should be fine, but regearing never hurt anyone. I’m looking for used Dana 35s up front and Dana 40s in the back, hopefully with lockers, but I live in the middle of nowhere so I’ll hold off on that one. I’m going to put an air locker up front and hopefully find a rear axle with some locker on it already, but I told my mechanic to find the axles for me because I’m just an ignorant 22 year old. I got 33 inch Falken MTs which I got a great deal on because my fiancé’s step dad is sponsored by them in offroad races. He mods Subaru’s -rolls eyes- honestly those things are stupid capable though, it scares me.
I could be wrong but I don't think the D35 was ever a front axle.
So regear. I'm not going to be exact on numbers but what you need is a low enough first gear with enough lift to be able to always start from a stop easily. Including in 4L on a steep, rough trail, but if first will always do that, your gearing is perfect.
Gearing for passing power in overdrive is backwards. Overdrive since its inception and common use 50 years ago is about dropping the rpms, extending engine life, providing a quieter ride, reducing the pollution exiting the tailpipe, and increasing gas mileage. The most efficient gear to put power on the pavement is the direct gear, not the overdrive gears.
A few years ago the Audi A8 came with an 8 speed automatic. It hit top speed, over 150mph in 5th gear, which is direct, and lost speed in 6th, 7th and 8th which are all overdrive. But it was one of the hottest sedans on the road, also one of the most luxurious. The Tundra 5 speed is direct in 3rd. 4th and 5th are massive overdrives..... which give it reasonable fuel economy empty.... and a 70mph cruise of 1800?rpm.
Point being, on the highway, you can always drop a gear, ot two, or three to pass or pull a grade.
The reason we cannot buy manual transmissions is because no one understands how to drive a manual. All the new automatics respond instantly to changing conditions. Shifting up or down as conditions change. Motors are engineered to work within a specifis rpm band. In the 1960s, when the 2speed automatic was GMs number one seller, that rpm band was brooad.... lift torque from 800rpm to peak horsepower at 5000 plus rpm. But that broad operating range made it inefficient and dirty. Todays engines are designed to run clean and at peak efficiency over a very narrow rpm range and the computer selects the gear to do that. I'll bet within 10 years nothing is built with a clutch. I'd also bet it will be illegal to regear.
The other fact, not related to cars is engines in marine or pumping applications. Designed to move a constant load of water they are built for peak power/efficiency at one rpm, the load never changes. As a result boats and fire trucks often deliver 30% more power than the same engine in a pickup. A fire truck with Cummins 5.9 feels absolutely sporty compared to the "same" engine in a Dodge.
Trust me. we 4x4ers are driving the legislation to ban regearing. Rethink that regearing philosophy.
