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-   -   General Re-Gearing Question (http://www.wranglerforum.com/f210/general-re-gearing-question-8252.html)

gcdcpakmbs 05-23-2007 01:44 PM

General Re-Gearing Question
 
What are max tire sizes (In general) given the following engines and gear ratios? I know that "what are you going to do with the Jeep, and what rear/front end do you have" applies as usual. So qualify your answer if you like.

4.0L 2.5L

3.73
4.11
4.56
4.88
5.13

AzTJ 05-23-2007 03:46 PM

THis basically applys for anything - http://www.oly4x4.com/gearratios.htm

1BLKJP 05-23-2007 03:46 PM

Thanks for posting that AZ. I had a great little post written up and then realized Donnie was messing with stuff and I couldn't send it. :D

AzTJ 05-23-2007 03:49 PM

lol -- no prob :D

Jerry Bransford 05-23-2007 04:43 PM

Quote:

Originally Posted by AzTJ (Post 84777)
THis basically applys for anything - http://www.oly4x4.com/gearratios.htm

Ratio guides like that are good place to start but they don't give the whole story. Like that guide only shows RPMs and it doesn't discuss all the in's and out's that make a ratio selection not so cut and dried. To read that guide, it makes 4.56 look as good as 4.88 for 35" tires, it's not.

What too few people realize is bigger tires do more than reduce RPMs which reduces power. They also have more rolling resistance, position the Jeep higher up in the windstream for more wind resistance, more mass to turn, and the bigger diameter gives the tire a longer radius for increase leverage against the drivetrain.

Better than most gear ratio guides is the collective wisdom of a lot of experienced Jeepers who know what ratios work well and what ratios are just so-so... or worse. :)

gcdcpakmbs 05-23-2007 04:52 PM

Quote:

Originally Posted by Jerry Bransford (Post 84807)
Ratio guides like that are good place to start but they don't give the whole story. Like that guide only shows RPMs and it doesn't discuss all the in's and out's that make a ratio selection not so cut and dried. To read that guide, it makes 4.56 look as good as 4.88 for 35" tires, it's not.

What too few people realize is bigger tires do more than reduce RPMs which reduces power. They also have more rolling resistance, position the Jeep higher up in the windstream for more wind resistance, more mass to turn, and the bigger diameter gives the tire a longer radius for increase leverage against the drivetrain.

Better than most gear ratio guides is the collective wisdom of a lot of experienced Jeepers who know what ratios work well and what ratios are just so-so... or worse
. :)

Well, that is why the question is posed.

Jerry Bransford 05-23-2007 05:20 PM

Quote:

Originally Posted by gcdcpakmbs (Post 84813)
Well, that is why the question is posed.

True. I didn't answer your specific question because you didn't ask for what would be appropriate for you and you didn't say what transmission you have. Ratios recommendations vary too much by engine, transmission type, final drive ratio, use, etc. to give recommendations for everything.

I could write a small book on all the good combinations common for Jeeps but I'd rather just concentrate on what your needs are. Your tire size, plans, transmission, etc. No one is going to want to write a white paper on all the combinations here. :)

Digger 5 05-23-2007 05:26 PM

In short, tell us what you really need (with all the specifics of your application) and we'll try to help.

gcdcpakmbs 05-23-2007 10:50 PM

That's fair enough. Not really what I was hoping for, but I understand. I've got kind of a horse and cart thing going. Without the proper knowledge, you start acquiring some of the wrong gear in the beginning...simply as a learning process. It gets a little expensive, and as a practical matter time consuming. So I'll start with one possible scenario, then perhaps create another scenario. If you stick with me, I will learn quite a bit.

D30/D35 4.0L Use as a daily driver, and as a dune runner. Will use only very occaisionally on beginner, and once more skills are developed intermediate rock trails. Mud would be very minimal. I've got plenty of clearance. (DPG OME 2" lift w/1.25 BL & MML, Discos, Adj Trk Bars) Currently a 3.73. I don't mind re-gearing. A D44 is in the future, but will happen when I find a deal on one used, or in about 3-years I'll just order one if I have to.

Trails/dunes 10%, Town driving 30-45mph 70%, Interstate speeds 20%.

I've been considering either steelies or American Racing Mohave's (black allow) in 15x8's and thinking 32's with the steelies or 33's with the alloys. (not 100% on any of this). Probably BFG AT's or MT's. In June I'll have an air bottle and winch.

Thanks

1BLKJP 05-23-2007 10:54 PM

Auto or Manual?

gcdcpakmbs 05-23-2007 10:57 PM

6-speed manual

1BLKJP 05-23-2007 11:03 PM

Hmmm, then with 32's you might be bumping down into 5th a little more on the highway with 3.73's. I run 35's on 3.73's right now with my 4.0 and auto. It does just fine in town and sometimes on steep inclines I have to hammer down in 2nd. But no big deal. I'd say that honestly you could live with it while you have the 35c in there.

gcdcpakmbs 05-23-2007 11:05 PM

Do you think the alloys v steelies will show any difference? The only reason I had for going with the alloys was they are lighter.

gcdcpakmbs 05-23-2007 11:24 PM

So the Auto is geared to produce more torque? Or is it that the Manual's top gear is just geared for gas mileage?

1BLKJP 05-24-2007 12:09 AM

No, I don't see any difference in the weight of the alloys vs steel wheels. I run alloy wheels on mine, but have driven plenty of lifted TJ's with steel wheels.


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