RPM with 4:56 gears - JeepForum.com
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post #1 of 2 Old 07-08-2020, 08:02 PM Thread Starter
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RPM with 4:56 gears

I've read all kinds of RPM and MPH statements for some time on these threads, and wondered about their accuracy,,possibly skewed due to vehicle condition, wind resistance from lift kits, additional weight increases from winches, bumpers, maybe torque converter condition. I just did a re-gear after multiple upgrades to my 1997 Cherokee. The Jeep has 134K, and seems to be in fairly good condition engine and transmission wise, all completely stock before modifications. Still no mods that should add any weight at this point. Seems to have lived an easy life, bought new as a fleet vehicle at a Veterans Hospital in Cape Girardeau Missouri. With advice and some dam good prices from Nick at Kolack Performance, a preferred vendor on this site, I have added the following,, 4.5 Inch IRO complete lift and suspension, upper and lower adjustable arms, adjustable track bar,, 5100 Bilstien shocks,, 31X10.50-15 Goodrich KM3 tires on stock 7 inch factory aluminum rims,, IRO Hack&Tap SYE,, 4 degree rear axle shims,, Eaton TruTrac LSD front and rear, with 4:56 gears. Brown dog complete motor mount upgrade, as well a Battery Cable upgrade. Also I am ASSUMING the tach is accurate. This is a 4.0 with the stock Automatic overdrive.Original gears were 3:55. I also upgraded the rear LSD Dana 35 to an 8.25 29 spline Chrysler rear end. I will say, I'm very pleased with the outcome, very glad I went with 4.56 vs 4.10. The increased power and drivability increase over the stock gears is a welcomed result.I also feel the 4.56 seems to compensate for the heavier tires.I also feel the 4.10's would have been a little steep.Much more power over the stock set up.
GPS says exactly 10 MPH off from unmodified speedo readings,, RPM at 60 MPH is 2150,,70 MPH is 2550. Cruising around town at 35 MPH shows 1150 RPM. The engine feels right at home and never seems to be pulling hard. Little to no "HUNT" as far as the transmission goes, barely ever downshifting at all. BTW, Jeep has never been driven in snow, just pulled out for the garage for a few days.

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post #2 of 2 Old 07-08-2020, 10:28 PM
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Looks great!
We have no snow here its still 90 degrees at 11.30 tonite.


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