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RPMs for AW4, 4:10s and 35s?

X

XJfire75

NAXJA Forum User
Location
Toonnerville, GA
Hey guys just curious on what kind of RPMs I'll be turning at highway speed on 35s. Tried searching but I don't think it really registers a search for "4:10s and 35s" lol.

Also any general ideas on how bad the speedo will be off?

I normally only have a hill or two in my daily commute and I drive like a grandpa lol. So I don't mind too bad about the sluggishness.

Beleive it or not I liked 32s and 3:55s. So 35s shouldn't be much worse at all.

Just up late and curious as to the RPMs from those who run my set-up.
 
http://go.jeep-xj.info/HowtoSpeedoGears.htm

this will tell you what speedometer gear will make it correct.

going by that chart, it should be similar to 3.55 with 30" tires. Or, in between stock and your 32/3.55. I have seen a chart with rpms and gear ratios, but I cant find the one I'm thinkin of right now. google time
 
Thanks guys. Yeah iv seen a chart too but a lot of them seem general not really specific for an XJ.

Wow didn't think it would be like 3:55s and 30s. I was hoping it wouldn't be much worse than when I ran my 33s and 3:55s. Good to hear that it might be better than 32 lol.

Thanks guys. Anyone care to chime in that's had this setup?
 
I run 35's and 4:10's. At 70 MPH I am at 2100rpms on a flat road. Hills you will be shifting to 3rd. Definately going to want a tranny cooler also. My speedo was dead on from 0-55mph, after that its about 4-5 mph off. Checked with a garmin GPS.
 
Cool man thanks. Yeah I've got like 1 hill that I'll shift outta OD for but other than that I'm in flat roads unless I'm wheelin.

Going to get the B&M cooler.

Looked at the grimmjeeper charts and I found out that my rpms will be close to stock gearing and 31s. Shouldn't be too bad.
 
It's easy to use percentages. For example, 35's vs stock 28's is .80. 4.10's vs stock 3.55's is .87. So 35's with 4.10's is 7% less rpm than stock. You can compare any gear and tire size this way very simply.
 
Charts and mumbers are great but they dont take into account the added weight of bigger tires, bumpers, winch etc. Also, now that you are higher your wind resistance is like a big refrigerator on sterouds goin down the highway.
 
The best method is to figure out how far you're off with the current gear, then apply a little math to figure out what gear you really need. Not all 35's are the same height. Some brands are barely 33" tall.

Keep in mind that the 1990 AW4 had a 0.705 4th gear ratio. The gear ration changed to 0.75 when the spline count changed in 1991 (?). That doesn't change what gear you need, but it will change the engine rpm you're cruising at just a bit.
 
Goatman said:
It's easy to use percentages. For example, 35's vs stock 28's is .80. 4.10's vs stock 3.55's is .87. So 35's with 4.10's is 7% less rpm than stock. You can compare any gear and tire size this way very simply.
Click to expand...

Never knew it could be put that way.

7% isn't bad at all lol


Oh and no heavy bumpers or winches for me right now. The gearing is a reason I'll just have my buddies hook their winch to me lol.

Tranny cooler and a temp guage is coming right after I get back from vaca to the Bahamas! Ha
 
XJfire75 said:
Thanks guys. Yeah iv seen a chart too but a lot of them seem general not really specific for an XJ.
Click to expand...

I posted a link: http://www.grimmjeeper.com/gears.html

It's a gear ratio calculator, not a chart.
Did you look at it?
It allows you to input what ever gears and tires you would like or you can pick from a pull down list of transmissions, transfercases, crawl ratios and rear ends...
 
Yeah I looked at it. I thought Id have to put in all the tranny numbers but I looked at it again after I posted that and found what I was lookin for. Thanks man.

Looks like I'll be in about the same RPM range as I would on 31s
 
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