Gear ratio poll for 37” tires on 17” wheels 3.6 gasser

[human29]

If everything else that I want to do to my jeeps was done, I would spend the money and regear to 4.88s even though my truck is doing fine with 4.10s on 37...

Unfortunately I keep finding new stuff to speed money on with my jeeps...

I will say this, if I didn't have the Banks Pedal Monster, I would have already regeared to 4.88...

I had a tuner with pedal control prior to re gear. Night and day on the road.

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[Panthers65]

Either way the 4:88 was the right choice for the 8 speed and 37s. restored back to factory shift patterns and on road RPM. The shop that I took this to was just doing the install as I was buying the gears elsewhere so it did not matter to them. Just took the advice of this jeep shop that does 2 -3 regears a week.

And if you're happy that's all that matters. I spent my time in a shop as well and we sold/installed hundreds and hundreds of gear setups. The different between 4.88's and 5.13's is minimal, <5% so the average person would never know the difference.

I will say, in all my years, I don't think I can ever remember someone complaining that they went "too deep" in a gear set (aside from the KOH and WEROCK cars we built, but that's an entirely different situation). I had quite a few customers "wish they would have gone deeper".

 

[Wheelin98TJ]

That chart is totally incorrect for a JL/JT with the 8 speed auto….

The chart Puddlejumper posted is for 1:1 at 65 MPH. It's not totally incorrect, it's just not for 8th gear.

 

[Minty JL]

I'm still on 4.10s with 37x13.5r17s right now, almost 20k miles and it has not been hateful.

I will regear to 5.13s and front locker sometime because I plan going up to 39s or 40s in the future

 

[Badweather]

Does a gear ratio versus rpm chart exist with the transmission in 8th gear

 

[Wheelin98TJ]

Does a gear ratio versus rpm chart exist with the transmission in 8th gear

Sorry, my previous post was confusing before I edited it. I was referring to the original chart posted when I said 1:1 at 65.

The chart @jwilson2899 posted is 8th gear RPM.

 

[Jteakus]

I do not own a 3.6 but have driven and ridden in many. They don't seem to make much torque but pull ok in the higher rpm's. Seems like deeper gears would be the way to go.

 

[Jteakus]

Best gear ratio calculator out there
Gear Ratio Calculator (grimmjeeper.com)

 

[JTGuy]

My 4.88s pull my 37s just fine. Anything from 2500 to 4000 rpm it pulls just fine. It's not fast but it's not a slug either.

 

[MrKnowitall]

There is no reason to go with 4.88 instead of 5.13. Even at 80, its only 2626rpm. That Pentastar wants every one of those revs to move a turbulent brick down the road. It'll shift less while cruising, won't use any more fuel, and give you the best, reliable performance. 5.13!

 

[PixelWelder]

I've got 5.13's on 35's. I haven't had a chance to read everyone's response, but what that chart doesn't take into account is the weight of the new wheels and tires. I thought 4.88's but the shop I went to told me if I'm towing... and I do, that I'll want the 5.13's. I haven't regretted it yet. I'm also in Utah and tow an RV trailer up some of these steep mountains.

 

[ttn333]

I think if you're a flatlander either will work on 37s. I was up at Big Bear in Socal this weekend. Even with 5.13s I wanted more going up. I was pushing her pretty hard keeping up with the traffic speed (55mph). I would have regretted going with 4.88.

 

[tom.mary.glad]

There is no reason to go with 4.88 instead of 5.13. Even at 80, its only 2626rpm. That Pentastar wants every one of those revs to move a turbulent brick down the road. It'll shift less while cruising, won't use any more fuel, and give you the best, reliable performance. 5.13!

Awesome username - MrKnowitall

 

[guntrust]

I have JTR stick with 37's and recent regear to 5.13 is my best mod ever. No longer dream of engine upgrade or buying a vette.

 

[Badweather]

Fantastic thread thanks all for the great reply’s and insights. Is a rebuild kit necessary on a low mileage gladiator I.e. less then 25,000 miles or any other must do’s if you regear?

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