4.88 or 5.13 on a Automatic
JK Enthusiast
Joined: Aug 2010
Posts: 151
Likes: 0
From: Winnipeg, MB
Personally, with all the talk about 5.13's being the 'best', I really don't see how the additional 100 rpms gained from switching to 5.13's from 4.88 is really that much of a benefit. 100 rpm is not a significant gain in the power curve or torque. I'll bet most who say they see massive differences really are just echoing what most others are saying.
Yea a bit more rpm can keep you closer to the sweet spot... that would be a benefit.
I did 5:13, 35's, and did a ProCal to reprogram my shift points and speedo.
I am very happy on road, and off.
JK Freak
Joined: Oct 2007
Posts: 524
Likes: 0
From: phx, az
I am pretty sure I will go 5:13's over 4:88 with my 35's and auto. My question is if I am going up a big hill like from Phoenix to Flagstaff, and it downshifts to 3rd gear, what rpm will i be looking at? I dont want to be at 5000rpm in 3rd gear.
JK Jedi Master
Joined: Jan 2008
Posts: 11,463
Likes: 165
From: Austin <--> Colorado Springs
Gear Ratios 1st 2.84
Gear Ratios 2nd 1.57
Gear Ratios 3rd 1.0
Gear Ratios 4th 0.69
Find the OD On rpm from the charts, then /.69
So assuming an auto with 5.13's and a 34" actual height measurement, you get 2450rpm @ 70 with OD On.
And OD Off is 2450/.69 = 3550rpm @ 70
JK Jedi Master
Joined: Jan 2008
Posts: 11,463
Likes: 165
From: Austin <--> Colorado Springs
It is bad for the MPG's. But from what I have read, this engine won't be hurt from rev'ing it a bit now and then. Pretty much everyone up here in Colorado drops down a gear and revs it up every time we head up I-70 