Bonedoc

Hey guys, like everyone else who has posted this I'm looking a little feedback.
I'm planning on running 37's. My Jk is an '08 Sahara with a 6sp manual ans 3.73 rears. I was considering just installing 5.13 and being done with it. looking at the chart in FAQ area, I'm not sure of the RPM's. Currently with stock tires at 70mph in 6th I'm turning about 2300 rpm. According to the chart with 5.13 I'll be 2600-2700. My truck is a daily driver with occassioanl offroad forays. On the highway 70-80 mph isn't out of the norm. Just want some feedback from people with manuals and the gear ratios they are running. I don't want to be screaming over 3000 rpm at 80mph.

Thanks

KenB1010

You don't discuss your lift here, so I'll guess at 3" for this discussion. 5.13's with 37's are a great choice. you'll have slightly better than stock performance, but your RPM's @ 80mph will be a little high. More importantly than that is your driveline speed will be very fast, which combined with your lift, gears, tires and your stated 80mph combine to vastly increase your chance of grenading your Transfer case.

In order to gain the high road speed that you want you will either need to give up tire size and/or some gearing or accept a much higher risk of wear and tear on your drivetrain.

nthinuf

Am I thinking about this backwards?

Taller tires would slow the driveshaft speeds? -Less revolutions at the same speed.
Shorter tires would speed it up? -More revolutions at the same speed.

But yes, driveline speeds are definitely a consideration.


And for the OP, plug in the numbers for a stock Rubi manual.
4.10's with 31" tires
= 2614 rpm @ 70

Seems to me that your rpm's with 5.13's would be pretty much, umm, stock... ?

wazooz2424

depending on the types of roads you drive mostly, you could get away with 4.88s and 37s with a 6spd, but 5.13s are better.

KenB1010

Your correct in your statement. Sometimes I write in shorthand. My concern isn't with the OP's choice of tires and gears, but with his stated use. At 80mph as a DD with very little off road use he will be making the choice of highly accelerated wear and tear on his driveline components.

I have the same setup that the OP is discussing, so far I have broken: 1 ring & Pinion, 1Transfer Case, and 1 Locker. mine isn't a DD, and the max I drive is 75 with most of my highway driving at 65-70

Serg5000

My opinion on this is you should call the guy's over at EVO. They deal with this everyday and would give you the best advise.

KenB1010

Ya, I did that. D60's with front coil overs on order. (:-))

mkjeep

Asshole.......

mkjeep

KenB1010

WOW, I expected something a little more eloquent from a moderator! Oops! Senior moderator! (:-)