Gear Ratio with 33's ??

[ChiefRocka]

Well ...

I have been driving the "poser" and must say I am happy with the ride.

However, I have to get this thing regeared ASAP, as it is guzzling the fuel !

Running a 33" Duratrac.

I looked over the chart(s) in the sticky above, but was told that a 4.56 would be best ??

I want it back close to where it was stock, maybe a tiny bit higher RPM would be ok ...

Thoughts ??

[ArmyGuy45]

4.10 if you do a lot of freeway driving or 4.56 if you do a lot of town driving.

[4.3LXJ]

John, 4.27 would be the ideal ratio, but that one is not available for us. So you have to choose between 4.10 and 4.56. As stated, the 4.10 would be better for highway driving, or 4.56 in hilly areas or if you are daydreaming of 35s

[Cheromaniac]

Running a 33" Duratrac.

I looked over the chart(s) in the sticky above, but was told that a 4.56 would be best ??

I want it back close to where it was stock, maybe a tiny bit higher RPM would be ok ...

If your tranny is the AW4 automatic, you'll definitely need 4.56's. If it's manual, go for 4.10's.

[ArmyGuy45]

http://www.rmr-offroad.com/interco/chart.jpg

[Mudderoy]

http://www.rmr-offroad.com/interco/chart.jpg

If I remember correctly this chart is based on a manual transmission and 60 mph. With 33's, 4.56 and at 80 mph I'm at 3k rpm

[ArmyGuy45]

If I remember correctly this chart is based on a manual transmission and 60 mph. With 33's, 4.56 and at 80 mph I'm at 3k rpm

Anyway we can find out? I am looking at 4.10s but if this is the case then I need to look for 4.56 for best MPG vs off road.

[gary63]

4:10 with 33 for MPG and highway driving becouse your RPM would be lower. 4:56 for better offroading you will run at a high RPM witch will make more hp and tork but use more gas.

[Cheromaniac]

4:56 for better offroading you will run at a high RPM witch will make more hp and tork but use more gas.

That's not necessarily true. Although the engine will be running at 11% higher rpm with 4.56's as compared to 4.10's, the extra 11% torque multiplication at the wheels will allow you to drive at the same road speed with a smaller throttle opening and with the engine under less load. Consequently, gas mileage may end up being the same.
A set of 4.27's with 33" tires will give you the same torque multiplication as the stock 3.55's with stock 27.4" tires, but 33" tires are much heavier so they require more engine torque to turn them, and the added lift increases aero drag. A set of 4.56's will compensate somewhat for the parasitic torque loss and higher aero drag and that's why I feel they're the right choice.

[cantab27]

4,1 in me tj running 33s 6 inch lift 5.2ltr v8.........and don't care about gas mileage.......ps I don't wave either ....:D

[Mudderoy]

That's not necessarily true. Although the engine will be running at 11% higher rpm with 4.56's as compared to 4.10's, the extra 11% torque multiplication at the wheels will allow you to drive at the same road speed with a smaller throttle opening and with the engine under less load. Consequently, gas mileage may end up being the same.
A set of 4.27's with 33" tires will give you the same torque multiplication as the stock 3.55's with stock 27.4" tires, but 33" tires are much heavier so they require more engine torque to turn them, and the added lift increases aero drag. A set of 4.56's will compensate somewhat for the parasitic torque loss and higher aero drag and that's why I feel they're the right choice.

The 4.56 gears are really nice off road. Up and over things is a breeze.

Here ya go! I was close, 65 mph...

http://img832.imageshack.us/img832/5971/tabelq.jpg

So if you took the AW4 out of overdrive and into 3rd, these are the RPMs you'd see.

Matt went with 4.10 and I think he's pretty happy with his choice. I like the pep of the 4.56's.

[Carves]

X 2 with Cheromaniac.

... Im running AW4, 30" tyres and 4.10 diffs ... and quite happy with the results. Nothing about fuel use or driveability - since the ratio change - has had me wanting to shove the original 3.55 diffs back in.

Factory stock should have been about 3.75, IMHO ... :smiley-scared003:

As mentioned already ... Dont get caught out by the ratio charts, with the pretty coloured in, sections ... they are all based on a final drive ratio of 1:1 ... which is 3rd gear in the AW4 auto ... and 4th gear in the 5spd manual.

The AW4 final drive/4th gear/OD ... is 0.75:1.


Probably the best ratio calculator to use is the one by GrimmJeeper.

Clicky click --> http://www.grimmjeeper.com/gears.html

... as it lets you play with tyre sizes, gear ratios, vehicle speeds and revs.

[gary63]

That's not necessarily true. Although the engine will be running at 11% higher rpm with 4.56's as compared to 4.10's, the extra 11% torque multiplication at the wheels will allow you to drive at the same road speed with a smaller throttle opening and with the engine under less load. Consequently, gas mileage may end up being the same.
A set of 4.27's with 33" tires will give you the same torque multiplication as the stock 3.55's with stock 27.4" tires, but 33" tires are much heavier so they require more engine torque to turn them, and the added lift increases aero drag. A set of 4.56's will compensate somewhat for the parasitic torque loss and higher aero drag and that's why I feel they're the right choice.
I agree with you on there is no exat set up that works for eveyone and a lot of thingscan change the outcome tire size tread design wheels weight acc. like winches bumpers roof racks lights and what is inside 1person or 4.I was just giving him the basic inf.. The best is trying things out until you find what work for you. for a exampleI have tryed diffent chips and reprogaming devises.
most will give you better throttle respons but in sand with the wrong tires you will dig a hole but in mud it will help clean tires and lunch you though the mud. But again you were right no one setup works for everone.

[ChiefRocka]

Well ....

We do take long freeway trips as well, though

Considering the fact that it is an auto, extra rolling resistance of the 33's, and the fact I do tow my 19.5' Big Block Jet Boat from time to time ....

I am thinking the 4.56 would be the way to go.
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http://i42.tinypic.com/23uzaed.jpg
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[Mudderoy]

Real world...

98 Jeep 4.0L AW4 transmission in over drive, 4.56 gears, 33x12.5x15 BFG MT...

4239

4240

[denverd1]

IMO its not worth doing unless you go 4.56. Especially, since you tow on occasion.

[cantab27]

hijack.. but since ya going to be towing with the old girl , I would look at putting in a after market oil cooler ....these trans hate heat and that's about the only thing to kill them ....ask me how I know ....:D oh water kills em as well but that's a different story ......:smiley-laughing021:

ignore post if shes a stick shift but ....;)

[gary63]

if you are going to tow 4:56 and cooler would be the way to go.

[ChiefRocka]

Oh ya,

Heat is the enemy to trannys

We always use overkill coolers on all our builds.

I thinking the 456 gear sets is where I'm leaning