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Discussion Starter · #1 ·
A R151F tranny has an 0.84:1 overdrive. Would it be possible to change that gearing to 0.75:1? Now, please realize that I know little about the internals of a tranny, so I may be asking the equivalent of can I stick glow plugs in my 2.7L. If so, Apologies.

Anywho, my thinking was this: If I swapped up to 33" and 4.56 gears, my highway speed at 2500 RPM would drop by 10 MPH. If overdrive was change to 0.75, then my highway speed would only be reduced by 3 MPH, and I would still have a slightly lower gear ratio than current. Add to that the horsepower mods I plan to add before the tires and gears and I'm golden at highway.

And then by leaving the lower gears intact, I would have significantly more power in the low range than I do now, perfect for playing in the mud.

So basically my thought was this setup would give me plenty of power when I went to play, and still hit 70 on the way to play without floating the lifters.
 

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Discussion Starter · #4 ·
I've seen those, but I can't find any, so far at any rate, that mate semi-easily to toyota gear. If I was running GM or Ford drive train, no worries. I like the idea, especially if an over/nuetral/underdrive were to exist. As in a crawl box and overdrive in one unit.
 

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Depending on how much you wanna speed this can be done. Stak4x4 is coming out with a three speed or is out that has 0.79:1, 4.33:1, and 1:1. There is a replacement transfer case for the truck. Just remove your old transfer case with this one.

I may be changing to this in 2 years.
 

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Marlin routinely installs Dyna R452 1st gears in the R151F for a 5.13 1st gear ratio. Ask him to send you the 5th gear out of a R452. Install it in your R151F for a 27% overdrive... You can't have both, it's either super low 1st, or super OD 5th gears. I don't know anybody outside of Australia doing this, so he should have plenty of the 5th gear parts with no demand for them. You'd still have the OEM R151F 1st gear ratio as well.:)
 
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