4:56 Gears
 

I just ordered 4:56 gears for front and rear axle. I plan to run 33x12.50 tires and wondering who else runs this set up and also what rpms you are getting with auto tranny (AW-4).

I would also like to hear from those running 35s. Thanx!

My 2001 has 4.56 gears and 10.50 X 33-15 KO2s.
At 60 MPH, reading off the GPS, it's turning 2300 RPM, read with a ScanGuage. This is similar to stock gearing.
Due to the extra weight, it didn't feel that fast, It would be interesting to run 4.88s with the 33"s. With the 4.56s, it was a lot of fun to drive when it still had 31"s.
It's more interesting to drive now, with a little help from Russ Pottenger .

Use this to find out your what your rpms will be, http://www.grimmjeeper.com/gears.html or use the formula and do the math yourself.

Stock gearing & tire size would be 1900-2000 @ 60 mph......

I've had 4.56 with 31s, 33s, and now I'm on 35s. I don't remember exact rpms, but it did fine on the highway with all of the tire sizes above. My 4.0 seems a little tired though so it would probably do even better with a strong motor.

Thanx for the replies. I have stock gearing now with 31s and I'm getting about 2100 rpm at 60mph. I'm just curious to see what the rpms will actually be with the new setup.

Have you changed your speedometer gear for the larger tires? With 31s and 3.55s, at 2100 rpm you would be going faster than 60 mph with 31s.

Have you checked you speed vs gps ? or mile markers on the highway ??

I ask, cuz I found out my speedo was off by a lot from the factory....enough so, that with stock gears and 31's, it is only off by ~2 mph @ 60 on the speedo.....as in 60 on speedo is 61.5 by gps.

and about the same rpm as you say you are getting.

I will have to do a gps check next time I drive it.

4.56 Re-Gear
 

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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