Stephane87

Questions since I'm lost and confused...

- 2010 Jeep Wrangler Unlimited Sport
- automatic
- right now I have 3.73
- 33" tires
- 90% city driving (flat)
- 5% highway (flat)
- 5% light off road

So what gears do I need if I stay with 33" tires? 4.56 or 4.88 or 5.13?

And if I go with 35" tires?

I tried to figure out the rpm chart but I'm lost :(

Thanks for the help...

PS: I don't want to kill my mpg..

DJ1

"Whitch" gears?

.....do those come with a flying broom or something?

Maybe they offer a package discount if ordering a "wench" too for the front bumper....

Stephane87

I'm so sorry if I did a mistake.... I think people get the idea of what I'm talking about

MotoJeeper

3.73s are perfectly fine with 33s. I would not even consider regearing with those tires. 35s, they will be ok with 3.73s. I run that and it only bogs down on steep hills at 75mph (I have the 3.6). If you regear with 35s 4.56 or 4.88 is good.

Stephane87

Thanks for the reply, I appreciate 😀

Joe_B

With the 3.8 and auto, you want 5.13s with 35s
You have a D30 front but with the driving you mentioned you will be fine. If you don't want to go 5.13s then at a minimum run 4.88s.

With the 33s I would just leave it alone.

The 3.6 & 3.8 are two totally different motors.

Mad Dog 21

So with that chart you have take a cruise at 70mph and capture your RPM's at that speed. Then take those RPM's to the new wheel size that you want to go up or down to. The color coding is basically the good,bad and ugly if you will. Hope that helps.

Wrangler428

I went from 33's and 4.10's to 35's with 5.13's. My mpg is the same and it drives great.

USMC20yrs

First you are going to need to do some research; you are going to need to know the gear ratio of your transmission when it is in drive. You can get this within this forum. Then you need this formula: MPH x Drive Gear Ratio x Diff Gear Ratio (divided by) Tire Diameter x 336 = RPM . This will give you the RPM of your current set-up (for the MPH number I use the speed limit). Then by working the formula in reverse, inserting your new tire diameter it will tell you what gear you need to maintain the same level of performance. For example: My JK is '13 6sp, stock tire dia is 29", 6th gear is 0.797, diff gear is 3.21; at 55MPH my RPM is 1613.6. So, taking that RPM as the starting point divide 1613.6 by 336 x by 33.4" (new 295/75R16 tire) divided by 0.797 divided by 55 MPH = 3.65 diff gear ratio needed. Since there is no 3.65 gear ratio available I would need a 3.73 gear in order to have the same performance as the stock set-up. However, something to also take into consideration is the increase in the weight of the tire and wheel (twice the weight of stock in my case). This will effect performance and MPG as well as braking. All this said, in my case, 295/75R16 with 3.73, I'm satisfied with it.

I hope this has helped and I wish you luck with YOUR decision.

Keep the shiny side up and don't forget to wave.

GoldenRubi

Why can't we help ourselves with this kind of stuff??? You took the words right out of my mouth.....