I have an auto, was curious to the guys who have 35's, did you upgrade your gears? If not, how does it run ?

 

Straight answer, no I didn't upgrade gears and I probably won't. I'm happy with the power I get with 4:10s, 35's, and the auto.

 

I still have my 3.73 s and dont see a lot of difference , I havent been on a long trip or anything but so far IM happy with 35 s & 3.73 gears...

 

I have 35's with auto and really hate my shifting all over the place on a somewhat flat highway......I am still gathering info on this topic and the majority claim 5.13 is the way to go. I just don't want the high RPM range if I'm cruising around 75MPH......I'm saving my pennies to get ARB's installed at the same time.....

 

I havent upgraded to 5.13's but will as soon as possible. It will definitely shorten the life of your tranny if you don't. My car drives fine the way it is..(auto/3.73's).. but extremely sluggish on interstate rides, which I do frequently. Off road I havent had any power issues, but have heard it's like adding 30 horsepower when you switch the gearing...I'm gonna hafta say it's a must with 35" tires

 

I am running BFG 35" with 3.73 and it is a pig, not enough pulling power. I will wait for the 4.56 gears to come out because the 4.88 and 5.13 are too low for 35" tires. Even a set of 4.27 would be ok for 35" if you only get to wheel once in a while. If you plan on running 37" tires the 4.88 would be ok.

 

I had 4:10's and went to 4:88"s when I added 35" tires. The gear change made a huge difference. I still lock out the OD once in a while. I would like to drive a Jeep with 5:13's just to see the difference. It is very noticable off road as well.

 

32/35 = ~8.6% change.

IE: Going from 32's, to 35's, lowers your rpm by ~ 8.6% from what it was.

Going from 3.73's to 5.13's will RAISE your RPMs by ~ 27%

IE: You would be LOWERING your RPM 8.6%, and COMPENSATING, by RAISING it ~ 27%

Essentailly, if you were to raise the 3.73 by ~ 8.6%, it would go from 3.73, upto a a 4.05 ratio....essentially the 4.1 that another post above said was, not surprisingly, fine.



An 8.6% drop in rpm is not that much, say you were cruising at 2,000 with 32's,...and swapped on a set of 35's...your RPM would go from 2,000 to 1,828 RPM.

That's a 172 RPM change....a fraction of a gear shift, and hardly noticeable, let alone paying a few grand to re-gear over.



(Most of the people who report giant losses on a larger tire swap are driving at the speedometer's indicated speed, and acellerating to the higher speed, which takes longer, and then feeling the damn thing must be sluggish, as it used to get up to speed faster, etc....or used to be able to maintain that speed up that steep hill, etc....)



Its human nature....happens all the time.

Of course, if you compare all of this to the OEM 3.21 ratio that they use to provide the best fuel economy....that's about 14% LOWER RPM than your 3.73 ratio...

...so, for best fuel economy, if you were cruising at 2,000 as above, the OEM gears would drop you 14% to 1,720 RPM, LOWER than the 35's would drop you.



Food for thought.

 

Teej, can you put that in english for this girl?

I don't understand yet the whole RPM/gearing/etc stuff and I'm really trying to get my head around it so I understand my jeep better.

 

basically her means that when you put taller tires on without changing gears your engine will be at a lower rpm and if you regear to a LOT lower gear your engine will be at a bit higher rpm range.

32 tires+ 4.10 gear = 2000 rpm@65
35 tires+ 4.10 gear = 1825 rpm@65
35 tires+ 5.13 gear = 2300 rpm@65

ALL NUMBERS ARE A ROUGH ESTIMATE and useing for clairification perposes only.