5.13 Re-Gear Question

[Mefford]

I recently had my Gladiator (see specs below) re-geared at a local shop to 5.13s. Everything seems pretty normal, 7th and 8th gears are back, it is very peppy now One small issue I seem to be having is the downshifting seems a little sharp into 2nd and 1st gear. Almost like if you shifted a manual and skipped a gear, my wife says she doesn't notice it. I did use my Tazer JL to set the gear ratio and tire size (36.71), I also had the gear oil changed at the 500 mile make and they said all looked good. I was just curious if anyone else that has had theirs re-geared has experience this or might know what the issue might be. Thanks

Jeep Gladiator Overland
Automatic Transmission
5.13 Gears
Dana M210 Front Axle
Dana M220 Rear Axle
3.5" Lift
37" Nitto Ridge Grappler Tires w/ Black Rhino Armory Wheels

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[Alabama Mud Machine]

5.13’s are a bit steep for 37’s with the 8-speed auto... 4.56 puts it back to stock performance, and 4.88’s (the most common ratio for 37’s) are a bit taller yet for a little extra low-end power. So, you could have over-geared a bit for your tire size to mesh up with your transmissions shift-points.

I doubt it will hurt anything, but something to take note of and keep a watch on.

 

[Jasonzj980]

I measured the tires (37x12.50x17 Ridge Grapplers) after mounted and at 28 psi and believe it came out to something right under 36 so I programmed it (Tazer) to that size vs stated size. Not sure how much of a difference it would be on what you’re experiencing though.

 

[LostWoods]

Do it if you enjoy acceleration. Getting back to stock ratio isn't enough when you are adding a bunch more weight further out on the tire.

You can go a lot deeper on these transmissions than you could in the past. On a JK, 4.88's were the norm because it has a .83 OD gear on the 5 speed AT. That is the equivalent of driving around in 7th on these transmissions. You would be doing nearly 80 with 5.13's before you hit the same RPM as a JK running 4.88's on the same 37" tires in top gear.

Like @Jasonzj980 mentioned though, you're likely losing a couple "effective" inches from the tire compressing on the bottom half. You'll want to measure hub to ground then double it to get what the rolling diameter is on your truck. 37's measure closer to 35" effective if you want to plug numbers into a calculator.

The only consideration is pinion tooth count (more == stronger) but I believe 4.88 and 5.13 are still both 8-tooth.

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