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Discussion Starter #1
Hi Guys
I'm putting in a 9" rear end in my 89 Cherokee and 33" tires.
It has an AW4 tranny with OD. and 242 transfer case.
I would like to be doing about 2500-2800 RPMs at 65 MPH.What gears should I go with?
 

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the differnece between 4.56 and 4.88 is 200 RPMS and a thinner ring gear.
 

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I wouldn't run 4.88 gears, an AW-4, and 33" tires, period. First, because you have an automatic, you don't need an ultra-low ratio for crawling, the automatic gives that to you already. For 33" tires and cruising at highway speeds even with an overdrive, your rpms are going to be excessively high at 70 mph with 4.88 gears. I'm running 4.88 gears and 35" tires and the rpms are high with my 5-speed which like your AW4, has an overdrive. 4.56 would be as low as I would go. There are some who will always pick the lowest gear ratio listed in the list of choices no matter what works best in reality. I strongly recommend 4.56 at the lowest for your 33" tires and an AW-4 4-speed automatic.
 

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Jerry, using you as an example to explain my above statement.
I calculate your rpm at 70 to be approx 2623 rpm w/ 4.88s in 5th gear. while if you had 4.56s it would be 2451 rpm.
Less than 200 rpm difference (regardless of you actual transmision ratio)
and anything above 4.56 (numericaly) in a dana has a Weaker ring and pinion.

ok I fixed my post:flipoff2:
 

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kidwired said:
Jerry, using you as an example to explain my above statement.
I calculate your rpm at 70 to be approx 2623 rpm w/ 4.88s in 5th gear. while if you had 4.56s it would be 2451 rpm.
Less than 200 rpm difference (regardless of you actual transmision ratio)
and anything above 4.56 in a dana has a thinner, weaker ring gear.
What? I don't know if you're considering 4.88 "above" or "below" 4.56 but a 4.88 has a thinner/smaller PINION gear. I'm really not sure what you're trying to saying at all. What is all this talk of a thinner ring gear? I sure as hell didn't notice the new 4.88 ring gear was thinner than the 4.10 gears, though of course there's a big difference in the pinion gear sizes. And with a 4.88 having a smaller pinion gear than a 4.56, for example, yet the case flange thickness is the same, the ring gear couldn't be thinner with 4.88 gears. Or am I just misunderstanding what your'e saying? :confused:
 

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I think they are thinner measured from inner diameter to outer diameter, not back to front
 

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kidwired said:
the differnece between 4.56 and 4.88 is 200 RPMS and a thinner ring gear.
I wouldn't worry about that on a 9" unless it is high pinion...but if you are running the 30 front it gets pretty bad.
 

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Discussion Starter #14
It's an 4.0 motor, I do alot of street driving.
and the lockup does work.
 

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stoneyxj said:
4.88 for better gas milage!!!! stoney
not on the freeway you're :smokin:

4.88 will be too tall for a 33" tire, your rpms will be way too high on the streets

check this out for a reference:

gear chart
 

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gripguru said:


not on the freeway you're :smokin:

4.88 will be too tall for a 33" tire, your rpms will be way too high on the streets

check this out for a reference:

gear chart
Thank you, here's another wheeler with some common sense about what's a good ratio and what is NOT a good ratio. :)
 

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I'm running 4.56 gears, a five speed, and pussy little 33s. For city driving it's perfect but on the highway mileage suffers because I usually turn 2800+ RPM. I actually think I'll get better mileage if I go to 35s, but than the crawl ratio is gonna suck big time! I've noticed my 1993 4.0 with 140,000 miles on it gets it's best MPG when turning 1900-2100 RPM.

Jes
 

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I'm running 4.88's with 35" MT/R's, a 4.0L and an AW4. 75 mph on the GPS is 2700 rpm (still waiting for my 'correct' speedometer gear)......


I'd do the 4.88 if you're mostly off-road and around town driving, and 4.56 if you're only occasionally off-road and mostly freeway driving with 33" tires. If you're driving an XJ, I'll assume it's a dual duty rig.....
 

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Discussion Starter #20
My thing about the gear chart is that with 31's and 3:55's I should be turning 2501.......I barely turn 2000 at 70!!:eek:
So if I apply that to my situation I should be turning 2720 rpm's with 4:88's and 33's
 
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