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4.56 gears

T

themauler

NAXJA Forum User
Location
Va Beach
I picked up some 4.56 gears front and rear for my hp30 and my 8.25. I don't go wheeling all the time so I cruise around on 30" street tires and save my 34" ltbs for the nitty gritty stuff.

How big will the change from 3.55 to 4.56 be on 30" tires? I am mainly focused on highway speeds around 65mph. I did the rev calculator but it just didn't seem to give me what I wanted to know.

Thanks in Advance

Nick
 
4.56 + 30" tires = no good....

It might also help us to know what transmission you have....

Manual:
AX5 - 5 speed manual - manufactured by Aisin - used with 2.8L V6 and 87+ with 2.5L I4
AX15 - 5 speed manual - manufactured by Aisin - used with 4.0L I6 engines

Auto:
AW4 - 4 speed automatic, electronically controlled - manufactured by Aisin - used from 87-01

Gear ratios:
Manual transmissions:

AX5 - 3.93 2.33 1.45 1.00 0.85 4.72(rev)
AX15 - 3.83 2.33 1.44 1.00 0.79 4.22(rev)

Automatic transmissions

AW4 - 2.804 1.531 1.000 0.753(OD) 2.393(rev)
 
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Multiply your current revs at 65 times 1.285 and you will get you answer (revs will be 28.5% higher). The 4.0 likes to rev so you shouldn't have any real issues.
 
As long as your doing 65 you'll be fine, it will just rev higher. If you have an auto w/ OD you'll be at 2324 which is perfect, with a 5 speed stick you'll be at 2656 (both #'s according to Randys R&P site) which is a bit high but still doable. If you ran a larger set of tires on it when you DD it that would help too, for every inch of additional diameter you will come down approx. 100 rpm. I'd say if you ran 31's instead you'd be a good, the up side is with all that gear it will be fast as hell around town which is always fun.
 
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robsjeepxj said:
...If you have an auto w/ OD you'll be at 2324 which is perfect...
Click to expand...

I believe I read that the best torque curve for cruising at freeway speeds was around 2100/2200 for the l6....



According to here:
http://www.grimmjeeper.com/gears.html

The RPM @ 65mph would be about 2500 w/4:56 gears and 30" tires.

It will work.... But image the kind of gas mileage you'll get. I know we are driving huge bricks with tractor motors, but gas is really getting up there....
 
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I have the aw4 so the revs don't seem that bad to me. I've never been a speed demon on the streets anyways. Thanks for the input guys. I will probably upgrade my street tires to 31s eventually
 
I re-geared two weeks ago, so I'll chime in. It's a 2001 I-6 w/AW-4 turning 4.10 gears and 31" BFG ATs. I'm doing ~2450 rpms at 70 mph. I would think you'd be pushing 3000 rpm with 30" tires and 4.56 gears. I would say that's a bad combination.

Keep in mind that the straight six "likes" rpms only when it needs them, i.e., towing a very heavy load. And that's only because it's better than having the engine bogged down. Just cruising the highway at ~3000 rpm will just be extra wear and reduced mileage.
 
Did the calculator and its showing about 2500. Got make sacrafices in life fellas
 
SPOBI. If you have no personal experience, you don't need to post. I ran 4.56s with 31s for over a year. It was awesome! My RPMs were fine. Prolly the best gas mileage my Jeep ever got! I know several folks running 4.88s with 33s and it works very well for them.
 
One of my best friends (and usual wheeling partner) ran around all last winter on 4.56 gears and 235/75/15 tires. He had no problems keeping up with me at 70 on the freeway and got damn near 20 mpg.
 
JPs01XJ said:
Keep in mind that the straight six "likes" rpms only when it needs them, i.e., towing a very heavy load. And that's only because it's better than having the engine bogged down. Just cruising the highway at ~3000 rpm will just be extra wear and reduced mileage.
Click to expand...

Except that people who run that configuration in a real world environment get very good gas mileage and show no extra wear at all. I run a stroker down the highway at 2700 RPM's all day long with no problems.

Up and down engines (inline 4, 6, 8 etc) don't have the problems with RPM's you get out of 'V' and most slant style motors. There isn't nearly as much thrust wear on the rings or cylinders - they just go forever. That's one of the reasons you see 22R toyotas and 4.0 XJ's as well as most honda's and such doing 300k+ miles and still running strong.
 
ExTankerGuy said:
SPOBI. If you have no personal experience, you don't need to post. I ran 4.56s with 31s for over a year. It was awesome! My RPMs were fine. Prolly the best gas mileage my Jeep ever got! I know several folks running 4.88s with 33s and it works very well for them.
Click to expand...

likewise, but unfortunately, the guy is talking about 30's.... so neither of us have first hand experience either.... right?

im not sure how much worse 30's are, but 31's+4.56 was fun... nice and peppy. cant tell you about mileage though, as i drive a jeep and dont care about mileage.
 
i also have a 01 XJ with a yet to be installed lift and 31" tires.
Also a daily driver AW4 3.55 combo that will be towing about 3600lb LBS around one in a while.

i was planning on 4.10 but have been thinking about 4.56. i ran both 4.10 and 4.56 in my old suzuki, and the 4.56 and 31" boggers worked well but with the lack of power i dont know if it can compare to my new jeep.

only problem i could have is that i work out of town often and need to drive for hours on end. not sure how well the 4.0 would like higher revs for hours on end??

the 4.56/31" combo in the zuke was good if you did not mind a top speed of 100KMH
 
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