At 60mph...
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Joined: Jul 2002
Posts: 904
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From: Bucks county PA
welcome to the world of 4.10's The best millage I ever got after alot of $$ thrown at it was 19. Stock I got like 12. Our other truck witch is alos a 98 12v 4x4 5 speed stock for the past 330k miles has gotton abotu 23mpg withi 33" tall and narrow tires and 3.54 gears. With my 4.10's I average low 17's high 16's. We've never towed heavy but even stock with 33" tires the 3.54 pulled 5000# on a dual axel car trailer and you couldnt tell it was back there untill you stoped.
Thread Starter
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Joined: Nov 2006
Posts: 205
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From: Greeneville, TN
Something doesn't sound right here. 2200 rpm at 60 mph sounds too high for that tire size, even for 4.10 gears. 2200 rpms with the transmission in 5th gear (.73), 285/75R16s (32.8"), and a 3.54 axle gear ratio should put you at about 80 mph. 4.10 axle gears would lower that speed to about 70 mph.
Have you actually clocked your truck over a known distance to check the accuracy of the speedometer? Seen if it takes 60 seconds to travel exactly 1 mile at an indicated 60 mph? If that checks out, I think that your tachometer may be reading too high.
Have you actually clocked your truck over a known distance to check the accuracy of the speedometer? Seen if it takes 60 seconds to travel exactly 1 mile at an indicated 60 mph? If that checks out, I think that your tachometer may be reading too high.
Registered User
Joined: Jan 2004
Posts: 122
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From: Akron, Ohio
I agree with Scramblinman.I have 4.10`s and 265/75R/16 tires[orig tire size 245`s.Adjusting for tire size i`m at 1800 RPM`s at 60,about 1950 RPM`s at 65,and about 2100RPM`s at 70.The overdrive ratio on my auto is .69 so if you have a 5-speed at .73 you will show a few more RPM`s.I`m a very conservative driver.I have never gotten less than 14.5 around town and usually get between 15.5 and 16.5.The best I`ve ever got was on the interstate with the cruise set at 60 - 21mpg.
Thread Starter
Registered User
Joined: Nov 2006
Posts: 205
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From: Greeneville, TN
I agree with Scramblinman.I have 4.10`s and 265/75R/16 tires[orig tire size 245`s.Adjusting for tire size i`m at 1800 RPM`s at 60,about 1950 RPM`s at 65,and about 2100RPM`s at 70.The overdrive ratio on my auto is .69 so if you have a 5-speed at .73 you will show a few more RPM`s.I`m a very conservative driver.I have never gotten less than 14.5 around town and usually get between 15.5 and 16.5.The best I`ve ever got was on the interstate with the cruise set at 60 - 21mpg.
Registered User
Joined: Jan 2004
Posts: 122
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From: Akron, Ohio
With 285`s [33" tall] your 4.10 ratio is reduced down to about a 3.78.I would save my money.I think your correction for tire size is off, or something.You should be doing 70mph@ 2200RPM with a 4.10 axle and 285`s.
Registered User
Joined: Jan 2004
Posts: 122
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From: Akron, Ohio
60mph @2100rpm with 33" tires would put your rear end ratio @ 4.56.I don`t think Dodge had that gearing as an option.I suppose you could have after market gearing installed by a previous owner.Either your tach is too high or your speedometer is reading low for 4.10 gearing.
