Optimal tire size for 4.56s gears and 42RLE?

VAUGHN01TJ

VAUGHN01TJ

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Can anyone tell me the optimal tire size for running this setup on an 06' X with 4.0 liter and 42RLE automatic trans. *Note this is a daily driver as well.
So I purchased the Jeep not knowing it had 4.56 gears. Came with 31" tires. Noticed the speedometer was 10mph over what it was actually running. Took it back to the dealership and they confirmed it had 4.56 gears. So that being said. I planned on re-gearing anyway as I was going to upgrade to 33 or 35 inch tires but now that I already have 4.56 gears the question is what would be the optimal tire size for this setup with the automatic trans. on a 4.0? Thanks guys!!!!!

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FWIW, my Jeep has 32" tires and 3.73 gearing. Using a GPS, at 65MPH, I'm about 1900 RPM. If I turn off the over drive, I'm almost 3000 RPM. This seems to match the gear calculator.
 
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You might need to get a new speedo gear to correct the speedometer, but if you're going to regear or change tire sizes soon, wait until you do that.
 
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04 TJ X with 42rle auto. I started of with stock 3.73 gears and 31" tires. Went to 32's, then to 33's. 33's and 3.73 was horrible. Had to press the OD off button every time I started it.

When I did my axle swap and 35's, I re-geared to 4.88 (deepest I could go at the time). It's bearable, I have overdrive back, but still feels like I need more. Sometimes I still have to use the brakes in 4lo to slow down on steep off road descents.
Here's the interesting thing. With a stock speedo gear, 4.88s, and 35" tires, my GPS and speedometer match when cruising down the highway.
The 42rle has always shifted into overdrive way too soon. I am going get another set of tires/wheels in the 33" all terrain flavor to run around on.
I'm guessing 33's on your 4.56 gears would act like my current set up, and a set of 32" tires would be ideal.
 
TJDaveX said:
04 TJ X with 42rle auto. I started of with stock 3.73 gears and 31" tires. Went to 32's, then to 33's. 33's and 3.73 was horrible. Had to press the OD off button every time I started it.

When I did my axle swap and 35's, I re-geared to 4.88 (deepest I could go at the time). It's bearable, I have overdrive back, but still feels like I need more. Sometimes I still have to use the brakes in 4lo to slow down on steep off road descents.
Here's the interesting thing. With a stock speedo gear, 4.88s, and 35" tires, my GPS and speedometer match when cruising down the highway.
The 42rle has always shifted into overdrive way too soon. I am going get another set of tires/wheels in the 33" all terrain flavor to run around on.
I'm guessing 33's on your 4.56 gears would act like my current set up, and a set of 32" tires would be ideal.
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TJDaveX, Thanks brother for the reply. Seems like 32's is the consensus here for this setup.
 
mrblaine said:
32's are optimal for 4.88's. 31's for 4.56, 33's need 5.13, 35's need 5.38.
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Makes sense. I re-geared to 4.88 with my 33s following the advice years back that 4.88 would be ideal. It wasn’t bad, but I did always feel like 5.13 would have maybe been a bit better. I guess when in doubt, I would rather have the gears a bit too deep as oppose to a bit to shallow.
 
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Chris said:
Makes sense. I re-geared to 4.88 with my 33s following the advice years back that 4.88 would be ideal. It wasn’t bad, but I did always feel like 5.13 would have maybe been a bit better. I guess when in doubt, I would rather have the gears a bit too deep as oppose to a bit to shallow.
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I am at 4.88 with 33s and the 42rle. I think on hills I could use a little more gearing, but on the highway it's beautiful. I may or may not go down to 32s with my next set of tires, but we'll see.
 
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2006TJ1 said:
I am at 4.88 with 33s and the 42rle. I think on hills I could use a little more gearing, but on the highway it's beautiful. I may or may not go down to 32s with my next set of tires, but we'll see.
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Yes, 4.88 gears, the 42RLE, and the 33s seems to be okay in most situations. Years ago that was the recommendation (Jerry recommended it to me when I re-geared my last TJ), and it works. I wouldn't have minded the 5.13 gears though, it would have given me a little more pep.

Hell, sometimes I wish I could gear even deeper than 5.38 with my 35s. Maybe I just like deeper gears ;)
 
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Chris said:
Yes, 4.88 gears, the 42RLE, and the 33s seems to be okay in most situations. Years ago that was the recommendation (Jerry recommended it to me when I re-geared my last TJ), and it works. I wouldn't have minded the 5.13 gears though, it would have given me a little more pep.

Hell, sometimes I wish I could gear even deeper than 5.38 with my 35s. Maybe I just like deeper gears ;)
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Hey Chris, thanks for the reply. I noticed in another post you used to run 31's on 16" moabs and mentioned you wished you had stayed with it. Just curious why?
 
VAUGHN06TJ said:
Hey Chris, thanks for the reply. I noticed in another post you used to run 31's on 16" moabs and mentioned you wished you had stayed with it. Just curious why?
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Because then I wouldn't have been tempted to go down the massive, massive money spending path I have now.

I'm into my TJ for almost 60k now, no joke. If you see my build list, you'll understand why: Project Pissed Off Wife: A Story of Indecision and Frivolous Spending

If I had stayed with 31s I wouldn't have ended up doing everything I did. The bigger you go, the more money you spend (to do it right at least). I certainly haven't skipped though on buying the best parts I could, that's for sure. So that doesn't help either!
 
Chris said:
Because then I wouldn't have been tempted to go down the massive, massive money spending path I have now.

I'm into my TJ for almost 60k now, no joke. If you see my build list, you'll understand why: Project Pissed Off Wife: A Story of Indecision and Frivolous Spending

If I had stayed with 31s I wouldn't have ended up doing everything I did. The bigger you go, the more money you spend (to do it right at least). I certainly haven't skipped though on buying the best parts I could, that's for sure. So that doesn't help either!
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Hey Chris, wow! I read your project pissed off wife. Ha! Sounds like you have a great build going though. Appreciate the feedback here and love the forum. Curious though, if I pushed the tire size to say 33's with my 42RLE tranny and 4.56 gearing. Would you anticipate needing much of the other upgrades compared to what it takes to do a proper build around say 35's.
 
Chris said:
Yes, 4.88 gears, the 42RLE, and the 33s seems to be okay in most situations. Years ago that was the recommendation (Jerry recommended it to me when I re-geared my last TJ), and it works. I wouldn't have minded the 5.13 gears though, it would have given me a little more pep.

Hell, sometimes I wish I could gear even deeper than 5.38 with my 35s. Maybe I just like deeper gears ;)
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Put a blower on it and you won't need deeper gears
 
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