Gear Ratio Question

Hi,

I'm a Wrangler Virgin and I will be changing my stock tires on my 06' SE to 31x10.5

I have already done the calculations and know which gear ratio I need, but I just wanted to ask, do I have to change anything else apart from the ring and pinion?

Like I say I am completely new at this, and probably wont attemp the job myself unless its very easy.

Any help would be appreciated.

Thanks

Changing the R&P is a procedure that takes a high amount of mechanical skill and special tools and gauges to do the job. It would help to have more information such a the axle types (Dana 35c,44 or other), transmission type (auto / manual) and what your expectations are.

Changing the R&P is a procedure that takes a high amount of mechanical skill and special tools and gauges to do the job. It would help to have more information such a the axle types (Dana 35c,44 or other), transmission type (auto / manual) and what your expectations are.

Thanks for you reply. In answer to your questions:

I have the stock axel Dana 35 i believe

Manual Transmission

Basically I understand that having 31" tires with my 3.73, will make it feel like I'm running a 3.18 is this true? I would just like to balance everything out. This sounds like an expensive job. Could you give some advice as to what I can do? My stock tires are pathetic. Generally when people get larger tires how do they compensate?

Thanks

You may want to live with the tires a while before going to the trouble or expense of changing gears. I drove my 98 TJ and 3.73 gears with 33" tires for 6 years. It is not the best, but you get use to down shifting. I only changed my gearing because I broke several teeth on my rear ring gear and one the pinion.

You may want to live with the tires a while before going to the trouble or expense of changing gears. I drove my 98 TJ and 3.73 gears with 33" tires for 6 years. It is not the best, but you get use to down shifting. I only changed my gearing because I broke several teeth on my rear ring gear and one the pinion.


Hey not to get off track here but My 01 TJ SE was in the shop last week because of a stolen PCM and I was at the Jeep safari in Moab so I rented a 06 Sport and a little bit into Fins and Things a 3 1/2 out of 5 trail I tore the hell out of the ring and the pinion gears barely made it out of there. My question is how hard are they to break??? I broke them so easy im going to be scared for awhile now with mine. I heard on the trail from some guys that they are hard as hell to break... was it maybe because it was a rental???

You may want to live with the tires a while before going to the trouble or expense of changing gears. I drove my 98 TJ and 3.73 gears with 33" tires for 6 years. It is not the best, but you get use to down shifting. I only changed my gearing because I broke several teeth on my rear ring gear and one the pinion.

Thanks for your reply. 6 years is a while, So you would have kept the 3.73 if you didn't bust you gears?

I'm happy to keep the gears, but I was under the impression the engine would have to work harder, and I wont even mention the ridiculous acceleration I will get... but I guess I didnt buy a Wrangler for the speed.

Incidently, how much did it cost to replace the gears?

Check out these sites, they will give you an idea of how your tire size will affect the ratio:

http://www.dakota-truck.net/TIRECALC/tirecalc.html

and

http://www.1010tires.com/TireSizeCalculator.asp

Both will give you an idea of the % that your speedometer will be off, which in turn will give you the % change in your effective axle ratio.

I'd have plugged in the numbers, but don't know what your stock tire size is.

Oh yeah, and also the Wranglers with the 30" tire package come with the 3.73 ratio, so 31" isn't that much more; DwightRGV has a good point - live with them for awhile, you may find they're ok.

If you have 3.73 gears, they should work OK for you.
The standard gear set for a Wrangler w/manual trans is 3.07.
The standard size tires are 28" with the 3.07s, with the 3.73s you could go up to 34" before you would reach the same RPM/MPH as the standard setup.
My Cherokee 5-speed has 3.07 gears. It seems a little high and it goes too fast in reverse, but I can live with the 22mpg I get with it, so I will leave it be.

Thanks for all your advice. I've decided to stick with the 3.73 gear ratio as I will probably only ever run a 31" tire because I'm not a hardcore 4 wheeler anyway :) Plus you guys seem to think its ok, and as you know way more than me I'm sure I'll be fine.

I may be wrong about this but isnt your Jeep a 4 cyl? I thought the 4 cylinder Jeeps with the 6 spd come with 3.73s.
I think that if you have the 4 banger with 3.73s and go to 31s, it will pretty much suck.

Good point, Ray. SE's with the 4 cylinder come with 4.10 gears.

Good point, Ray. SE's with the 4 cylinder come with 4.10 gears.

They used to prior to the 6 speed tranny. Ill have to check this out but I think if you go to Jeeps website, they show the SE with the 2.4 and 6 speed as having 3.73s.

They used to prior to the 6 speed tranny. Ill have to check this out but I think if you go to Jeeps website, they show the SE with the 2.4 and 6 speed as having 3.73s.

Mine is the 2.4l 6-speed and it does have the 3.73 gears. So you're saying bigger tires are gonna suck with my engine? I know I'm going to be slower, but do you think its going to be ridiculous?

They used to prior to the 6 speed tranny. Ill have to check this out but I think if you go to Jeeps website, they show the SE with the 2.4 and 6 speed as having 3.73s.

Oops, forgot about the 6 speed.

Mine is the 2.4l 6-speed and it does have the 3.73 gears. So you're saying bigger tires are gonna suck with my engine? I know I'm going to be slower, but do you think its going to be ridiculous?
Did you go to the websites I suggested? The % change will be the approximate % change in power to the wheels also. You'll usually lose some acceleration with larger tires.

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OK, I went and plugged in the numbers for the 215/75/15's vs the 31" tire.

The new tires will be 10.6% larger.

Your speedometer will read 11.83% slow, showing 53 mph when you are doing 60 (unless you have it calibrated)

So by the numbers you'll lose about 10% of your acceleration, all other things the same.

IMO have a 4-cyl in a Jeep sucks with any size of tire.
It all depends again on your expectations.
You could always add a turbo later on, I guess. That would raise your power to about the same level as the 6-cyl.
The nice thing about the 6 is the torque while idling and just above an idle, makes it much easier to crawl over rocks and stuff. Many times you can let it idle when with the 4 cyl you actually have to work the throttle. It can be more challenging. My Dad always tells me, "a professional can work with anything and get results". So with more skill than I have, you may do just fine.

Mine is the 2.4l 6-speed and it does have the 3.73 gears. So you're saying bigger tires are gonna suck with my engine? I know I'm going to be slower, but do you think its going to be ridiculous?
I think you will almost never use 6th gear, especially if you live in a hilly region. I also think you will have to slip the clutch alittle more to get rolling. I cant really say how bad it will be because Im not familiar with the gear ratios in the 6 spd. or the powerband of the 2.4. Im certain there will be a noticable difference though. How tolerable it is really depends on you. You should be able to keep up with traffic fine, with the exception of long uphill grades.

Fredjacksonan - I did check out the websites and I got the same results. I didn't realise however the % difference is what I would lose in acceleration also. Its nice to know, although 10% acceleration loss does not bother me that much. To be honest I live in New Mexico and everyone here drives like they have dynamite up there ass, so I'm used to getting passed all the time whether I'm ragging the Wrangler or not. :)

NeonRT - I have considered a turbo but not for a while. It would be interesting to see the performance gains though. I'm probably not as skilled as you yet because this is my first Wrangler, but I'm sure I'll do ok with a bit of practice.

RayH - New Mexico is full of hills so you are right I hardly ever use 6th, and I do slow down considerably when taking on a large hill. With the traffic however it is pretty nippy, but to be honest I love just cruising at the speed limit.

IMO have a 4-cyl in a Jeep sucks with any size of tire.
It all depends again on your expectations.
You could always add a turbo later on, I guess. That would raise your power to about the same level as the 6-cyl.
The nice thing about the 6 is the torque while idling and just above an idle, makes it much easier to crawl over rocks and stuff. Many times you can let it idle when with the 4 cyl you actually have to work the throttle. It can be more challenging. My Dad always tells me, "a professional can work with anything and get results". So with more skill than I have, you may do just fine.

I have an 01' 2.5 5 spd with 31's and I have no problems it also has the 4.11 gears but like you said I do have to work the gas a little 4 lo is great though!! I rented a 4.0 and there is a BIG difference in power but in LO I didnt feel like I had the "crawl" I would like. It had 33's

I don't remember what I paid for just the gears, but a quick online seach will give you a good idea. (I also put in lockers, a short-shaft conversion, driveshaft, and springs. The total was a bit more than I want to scare you with.) I don't know when I broke my gears initially, but I drove around with a missing tooth on my ring gear for at least a year after I noticed it. And with all the damage it had, I never really noticed (but it did make me a bit nervous on long isolated trips). So my advice... Get the tires you want, and live with them a bit. Yes you will feel underpowered at times, but trail-wise you'll likely be o.k. And when you finally break your ring gear from off-roading (or an ice patch, etc) you'll know that it's truely worth changing gears.