Whitch gears?
 

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..

"Whitch" gears? :thinking:

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

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

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

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.

Thanks for the reply, I appreciate 😀

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.

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.

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.

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.:standing wave:

Why can't we help ourselves with this kind of stuff??? You took the words right out of my mouth.....:rotflmao2:

It just kept on pulling at me......so I gave in lol :rotflmao2:

As I told her in PM, just a friendly "ribbing" :)

As you can see, the name say "Stephane".....so maybe I made a mistake in "witch" because english is not my first language....but I actually know the difference between a man and a woman name.

PS: I'm a man, just in case you didn't figure it out. Just a friendly "ribbing" :)

I thought your name was "Steph" :rotflmao2: ....which is short for Stephanie

The pic leads to believe that it's a super hot chick with a nice rig.....that's false advertisement!!!!!!!!!!!!

That's a quadratec ad pic from over 5 years ago

Even after 5 years, it's still a hot pic

So guys, let's focus on my "gears" question and not the girl on the picture😀

Did you say girl??? :rotflmao2:

No, seriously, you should leave it as is with your 33'' tires. 3.73's are perfect. IF you did more off-roading than city driving, then 4.10's would be a bit more appropriate. When you decide to go with 35's, 4.10's would be ideal for mostly city driving, 4.56's would be bringing your RPM's up to about 2400 for highway driving. 4.88's with 35's would be a tad much. Stick with what you got now and if you do decide to go with 35's, 4.10's would be perfect for you. Don't try to over-gear it and have your engine way rev'd up all the time just for the sake of saying that you have taller gears. That's just my 2 cents.

I don't think your gearing would be horrible with 3.73 and 33's. My rubi had 4.10 on 32's and to be honest it was pretty low. First gear (manual tranny) took me about 40 feet. There are some good gear ratio calculators out there to steer you in a better direction. I've been running 35's with 4.10 for a couple of months now. I'm planning on 37's with 4.88.

Edit I removed suggestions pending further input.

It is important to make sure you have calibrated your computer with a procal or flashcal. If you don't tell the computer your equipment is different the shift point on your tranny will not be correct and will cause a reduction in fuel economy.

I just read this chart. It seems like everything is really low. Anyone with a 3.8 auto have some insight?

Attachment 615996

Much much much easy way is to take new tire size , yours is 33.4÷29(old tire size) then multiply by current gear ratio which is 3.21which is actually 3.697

Why do you divide by 29? My stock 2010 JKU sport came with 32"...was is already an upgrade that I didn't realize? Because if I do the calculations with 32" as the stock size then a 40" tire would only need something close to 4.66 (gears)....doesn't make sense?!?!?!

Size isn't the only part of that equation. You also have to think about rotating mass. A 40 is a lot heavier than a 33. Any extra weight in the tires is like having 5 times that weight difference in the back of your Jeep, therefore making the need for a higher gear ratio to turn the extra mass.

Ok, but do I still do that calculation base on a stock 29" or 32" (in my case)?

My example would be: 33" / 32" X 3.73 = 3.84 (stay at 3.73) or 33" / 29" X 3.73 = 4.24 (go up to 4.56)

A good way to find out you originally equipped tire size, is to go on to jeep.com and look up your build sheet using your vin#

Good idea, thanks a lot

For a 33, weight doesn't do much. I was talking about bigger sizes like 40s.

You can also find out what gears you have when looking at your build sheet.

With the 3.8 auto and 35s you need a minimum of 4.88s. 5.13s would be a better option but people don't like running them in a D30.

It's not complicated.

Also you need to look at actual tire size when mounted and not what the manufacturer specs say.

There are a million gear threads. And those people who are chiming in about running manuals or the 3.6 you aren't really helping the guy.

I would leave the gears as is with 33s

Like Joe said ..... Don't need to make this so complicated !!!!
I have an 09 JKU auto I ran 5:13 gears in my Dana 30 on 35's I did eventually blow the gears wheeling. So if you wheel it I'd probably stop at 4:88's tho the 5:13's were nice. I now have a PR44 up front and 37's and the 5:13's still works really well with my set up.
If you're staying with 33's I'd save the money and not re gear.

Thanks

I was referring to his math. For you u take your new tire size of 35. Divide by 32 then multiple by stock gear. I have 3.73 stock which means I need just over 410s. I'm going to go 456. Keep in mind also that your stock 3.21 have no business being in a jeep. They are the stupidest gear ever put in a wrangler.

Don't mean to hijack the thread, but I was curious how it was with 35s and 5.13 gears. I want to regear soon. Did you notice much difference, like did the Jeep pick up speed a little faster?

My stock gears are 3.73...

Regardless of the stock gear ratio, i'd look at the gear charts for your model. They use transmission gear ratios for your model with corresponding engine rpm's.

If it was me I would go with 4.56 with 35/37s on a 2012+ jeep if you spend time on road. 4.88 if a lot off road or hill country. If going larger than that tires you have much more to worry about

^ USELESS!! He drives a 2010 as he CLEARLY wrote in his opening post.

I wheel my jeep often and live in the foot hills of Appalachia I run 35" bfg km2s with a six speed and 4.10s I love it I don't feel as I need a deeper gear set, and despite all the warnings and naysayers when these 35s are gone it's getting 37s bolted back in their place.

www.overlandoff-road.com

Another USELESS post as the OP CLEARLY wrote he drives an auto to open this thread

Thanks rob for your useful insight

www.overlandoff-road.com