37s & O4OD & gears... 5.13 or 5.38?

[NikBraap]

Going 37s... need to re-gear, besides some other modifications.
351w & E4OD

I was playing around on http://www.grimmjeeper.com/gears.html and was wondering who is running 5.38 with 37s.

I have 35s and 4.56, but in OD /4th it is too weak for my taste. Slightest incline, need to downshift in 3rd.
It goes up by +252rpm at 70mph and +289rpm at 80mph comparing 5.38/37s and 4.56/35s.

5.13/37s seems too close to 4.56/35s >> only goes up by 139rpm at 70.

I am not trying to break the speed barrier and I take my time, so I hardly go faster than 75 anyways, when on highway.


(should say 4.56 on the right side)



Who has 5.38 with 37s and can share some insight?

Much appreciated!

[damon1272]

I currently have the same drivetrain and gearing as you with 35's. You are right on As for 5.38 I think that you would be right in the ball park as I think the 35's should be 4.88. That said what rear end do you plan to run this gearing in 8.8? or 9 in.

[NikBraap]

Exactly, I should have went 4.88 with the 35s.
9 inch, spool, 40spline

[funinthesun95]

OD can handle the 5.38 I would do that if your not a 85-90 freeway guy.

I have 4.88 with the 37 but I have a usshift Tranny control unit and have changed the shift point to work better with the 4.88. With out that 5.13 at a minimum 5.38 would be best to help move our heavy babies.

[NikBraap]

Yep, taking my time on the freeway. Pretty much set on 5.38.
Some tires are not true 37s, but that's another story. Same with a lot of 35s, they are a bunch smaller with 30psi.
Thinking about toyo M/T.