Erikwt

So I thought having a hemi would also mean not having to change the gears from 3:53 to 4:11's (or 4:56) but it was recommended that I do upgrade. Have 3.5 lift with 35's.
Has anyone driven a 5.7 jk w/o the gear change then one with upgrades?
How different and is it in fact better?

horrocks007

I wish I could answer you. (Then I'd have a V8). But I think it maters more the transmission used in the swap.

Erikwt

Yeah not 100% positive about the trans. Whatever is with the kit.
My thought was always that with the stronger mtr you don't need the gear change and if changed, you'll have less axl turns per shaft rotation, causing not less power but less speed.
Am I right or am I missing something here?

scubatech

Erik,

I have a 2014 Hemi / 4.10 gears, 35" tires and it works great. Now if you have the pre 2012 with 545 trans then you have an overdrive .69. That is likely why you're being told this. The gears in a Jeep usually go; 3.21,3.73,4.10. So when you shift to OD the rpm drops too far. If you like it though that's what matters.

Erikwt

It's an '11 with the swap done in '13

Blizz

Man, I wish I had this problem! Sorry I can't help you answer your question!

scubatech

Erik,

You will have the 545 trans then with .69 OD. I'd go off the feel of it. You might be fine off road. I know up here in the altitude that high OD feels flat even with the V 8.

Earth Siege

So u have been driving it with this combo for a year and a half already?

When going 55 in oveddrive, what is ur rpm average?

How does it feel. Luggy, slow to respond? Weak. Constantly shifting out of lockup or overdrive on the slightest incline?

If not then leave it alone. If yes then gears may be good option. For the amount of difference between them, it will improve power feel at all speeds, shift sooner and at lower speeds, and have a slightly reduced top speed, not that it matters. Will most like negatively affect mpg.

The more powerful it feels, the less impressive the mpg. Its a balancing act.

tarpon4me

I've never had a jeep with a V8 in it, but I've had plenty of trucks with V8's and larger tires. If you are going to spend the cash to do a motor swap, get it re-geared properly. Even with a V8, if it's anything like a truck, it will still be a dog. Will it be less noticeable with the bigger motor? sure... But part of getting that power to the pavement is gearing for your tire size. It's a night and day difference with a V6. I can promiss you the difference is no less with a V8.

Elusive

I have a 2011 vvt hemi with the 545 trans.
I'm running 38's and 5:13 gears. feels perfect. 60 MPH is exactly 2000 rpm.
do it right and re-gear that beast. It makes a HUGE difference