4.10 or 4.56? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 09-20-2001, 06:59 PM Thread Starter
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4.10 or 4.56?

I've played with the gear ratio calculators, but I want first hand knowledge. I'm going to replace my 2.73's with 4.10 or 4.56 gears. I have a ford 5.0HO and WC T-5 overdrive). I don't plan on highway driving over 70mph (and 2500-2700 would be a nice cruise rpm).

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post #2 of (permalink) Old 09-20-2001, 07:08 PM
 
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Re: 4.10 or 4.56?

What size tires? I have almost the same drivetrain (T-18 instead of T-5) and I find 4.10's to be a pretty good compromise between street and offroad with 33" tires. I run about 3K in 4th (1:1) at 65-70mph.

'79 CJ-7
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post #3 of (permalink) Old 09-20-2001, 07:23 PM
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Re: 4.10 or 4.56?

Most people go with 4.10 gears with 33 inch tires and 4.56 gears with 35 inch tires, unless you're into serious rockcrawling, then you might want to go with even lower gears, but expect to burn a lot of gas on the highway.

Steve

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post #4 of (permalink) Old 09-20-2001, 08:00 PM Thread Starter
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Re: 4.10 or 4.56?

I forgot to say I have 33" MT/R's

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post #5 of (permalink) Old 09-20-2001, 08:33 PM
 
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Re: 4.10 or 4.56?

How do you like those MT/R's? I'm seriously looking into buying a set.


'93 Amigo XS 4x4
2" susp. 31x10.50R15 Pirelli Scorpion AT's, Rancho 5000's, tons of engine/exhaust upgrades
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post #6 of (permalink) Old 09-20-2001, 08:44 PM
 
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Re: 4.10 or 4.56?

Might want to look into Interco's newest tire, the Super Swamper TraXus. How do you like the Amigo? What type of 4-wheeling do you use it for? I almost had one as my first vehichle.

Make it up as you go.
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post #7 of (permalink) Old 09-20-2001, 08:51 PM
 
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Re: 4.10 or 4.56?

I love the Amigo, wouldn't trade it for the world. This is actually the second one I've owned. I do mainly dirt/rock crawling in the summer, mud up to 1' in the spring and fall, and deep snow in the winter. Here in Indiana, we get all different conditions to play in!


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post #8 of (permalink) Old 09-20-2001, 10:03 PM
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Re: 4.10 or 4.56?

zimm how is the WC T-5 holding up. My NWC T-5 just lost reverse so I was thinking WC T-5 but am worried about doing the same to it.

Have you have any problems with the WC.

As far as gears I calculate it as fallows.

5280 X 12 / (tire height X 3.14) = turns per mile. for 33 inch tires this is 611. NOTE: for a more accurate tire height measure the distence for the ground to the center of the hub and times by 2.

turns per mile X speed / 60 = RPM of rear wheels. For 33's at 70 MPH this is 713.

Now we must get the engine RPM's to the wheels. Ratio = Engine RPM / (OD X RPM at rear wheels). For 33's at 70 MPH and 2700 engine RPM this is 4.56.

Here are some other ratio's at 70 and 55 MPH

Engine RPM = RPM at rear wheels X axle ratio X OD.


here are my results for 33's at 70 MPH.

ratio ........ Engine RPM
3.07 ........ 1817
3.54 ........ 2095
3.73 ........ 2207
4.10 ........ 2426
4.56 ........ 2699
4.88 ........ 2888


For 33's at 55 MPH

ratio ........ engine RPM
3.07 ........ 1427
3.54 ........ 1646
3.73 ........ 1734
4.10 ........ 1906
4.56 ........ 2120
4.88 ........ 2269

I hope the above is of some help. If you only are trying to improve your crawl ratio then a lower transfer case gear set might be a beter choice as it will not harm your highway gearing.

bandhmo

post #9 of (permalink) Old 09-20-2001, 10:10 PM
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Re: 4.10 or 4.56?

bandhmo, good info, but I havent seen those results, or perhaps my 5th gear in my nv3550 is a different ratio. 70 mph gives me about 2300-2400 rpm with 3.73 gears, a 4.0, and 33" tires (with a true diameter of about 32.5") in 5th gear. I havent measuered it in 4th, but I would expect the numbers to be closer to what you have.. did you divde the O/D?

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post #10 of (permalink) Old 09-20-2001, 10:44 PM
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Re: 4.10 or 4.56?

Thanks elusive I did make a mistake. The above post is now corrected.

I used a over drive of .83 for the T-5. I am not sure how this relates to the NV3550.

bandhmo


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