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-   -   Gearing (https://www.wranglerforum.com/f290/gearing-2248434.html)

Batjac 03-10-2018 12:28 PM

Gearing
 
I know this horse has been beat to death but I have been unable to do a search to find my set up and gear question. I have the 4.2, auto, 15" tire, 3.07 gear set up. It will scoot down the road but off road it wouldn't pull a greasy string out of a cats butt. It will go good enough I guess but I would rather have more low range in 4WH when doing trails. I do not do any ruff stuff, not interested in rock crawling or mud bogging, just easy to moderate trial riding. 4WL is to low IMHO so I would rather have something lower for 4WH. The jeep spends most of it's time on the road, local stuff, no highway. I am torn between 4.56 and 4.10, I am afraid which ever one I do I will wish it had been the other. I also plan on a locker for the front. As of right now there is no plans for larger tires, I have a 1.5" lift and it's all I can do to drag my old butt in it now. Thanks for any feedback.

Gottagofast 03-10-2018 12:58 PM

You have 15" rims not tires.... the important number is tire height... I'm guessing you are on 31's
Unless you are really flying (35 plus mph) you should be using 4L offroad.... much better for your trans.
W a 3 speed auto and 31's for mostly road driving I wouldn't want any lower than 3.73 gears... 4.10 gears would raise your rpm's @ 30%... ie 2000 becomes 2700

Batjac 03-10-2018 04:41 PM

Quote:

Originally Posted by Gottagofast (Post 32897538)
You have 15" rims not tires.... the important number is tire height... I'm guessing you are on 31's
Unless you are really flying (35 plus mph) you should be using 4L offroad.... much better for your trans.
W a 3 speed auto and 31's for mostly road driving I wouldn't want any lower than 3.73 gears... 4.10 gears would raise your rpm's @ 30%... ie 2000 becomes 2700

You are correct, I meant 15" rims. It is bone stock, the tires are P235/75R/15. And they measure 28" tall. The problem is now if I am on a trail or going up a hill on the road it will fall on its face because it's not building any kind of rpm's.

Gottagofast 03-10-2018 04:58 PM

Honestly 3.07 should be pretty good.... maybe you have engine issues and aren't making the power you should...

When you encounter a hill, as you give it more throttle it should be downshifting so it can rev up and pull the hill..... maybe you have a kickdown linkage issue....

Batjac 03-11-2018 10:05 AM

No the power is good and it will downshift fine, the issue is putting around in the woods and not generating low end torque when I want it. Also going down hills you have to stay on the brakes or it generate way to much speed and I guess the bottom line is I just want a lower gear for those reasons, just don't know what I want. I can only relate low gears from the old hot rod days so I don't know if 3.73, 4.10, or 4.56 is what I want. Any insight on gearing and what I can expect to get with my present set up will be greatly appreciated.

Gottagofast 03-11-2018 01:08 PM

https://www.ringpinion.com/calculators/Calc_RPM.aspx

Figure out what the max rpm that you would be happy running at your highest road speed and play with numbers for the lowest ratio that will still be acceptable to you at high speed.

I did that for my preferences and your specs and came up with 3.07....

Maybe you are ok w a top speed of 65 turning 3650 rpm in which case you could go with 4.56 gears.... I wouldn't be....
Fwiw with your current gears you will turn almost the same rpm in 2nd gear as you would have in 3rd w 4.56 gears.... sooooo easy test.... go take a highway drive in 2nd gear and see how you like it

The slower you are moving the less difference the rear end ratio will make...

Example switching from 3.07 to 4.56 will raise your rpm's by 250 at 5 mph in 1st gear and 1250 at 65 mph in 3rd gear....

Offroad, low range is much more effective at solving the issues you mentioned.

Onroad, you are contradicting yourself... first you say it falls on it's face and doesn't make rpm's and then you say it downshifts fine and makes good power.... can't be both

Batjac 03-11-2018 07:53 PM

Yes/no, it does run good, downshifts fine and the motor runs great just doesn't have the low end I would like, on the same hand I don't want to be running to high RPM's as gas millage is not much now. You have some great points and some stuff to think about, maybe I should just be content as you are correct in I can not have both, low RPM road speed and low end torque on trails. I could use 4WL and have tons of torque, to much and to low to be honest but 4WH is at the other end so I may just leave it as is. Thanks for some good feedback and some interesting view points.

Gottagofast 03-11-2018 10:21 PM

No prob... not having overdrive limits your jeep more so than one w it...

Not to sound like a broken record but really give low range an honest try.... sometimes my club hits the trails w more than 20 jeeps and every single one of them shifts into low range as soon as we leave the pavement.... I regularly hit 35 mph or more in low range

Gottagofast 03-13-2018 12:31 AM

FWIW w 28" tires 3.07 gears and your 2.72 low range you will see very nearly 1000 rpm for every 10 mph in 3rd gear.... IE 18mph would be 1800 rpm


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