Gearing 4:56 or 4:88?

89wrangler

89wrangler

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Joined
Oct 22, 2005
Location
Bostic,NC
15 Rubicon,3.6. 5spd auto, 3:73 gears...... I will be changing the gears in the near future to accommodate a 37" tire. In my research it is saying that 4:56 gearing would be the best. I am going to say this will see 75%/25% road/trail miles. Being that most tires will be more like 36" I am kinda agreeing with this. But I only want to do it once. Anyone have any real world experiences with 4:56 vs 4:88 for highway driving?Thanks
 
I'd go 4.88, those 3.6's shouldn't be afraid of a little rpm. Barely a 200 RPM difference at 70 between the two ratios using 36" as the tire diameter. 4.88's at 70 shows 2656 RPM and 4.56's show 2482 RPM. @Jason W. has had 4.88's and 5.13's in JK's and could give some real world feedback.
 
Definetly 4.88, bug reason you live in the mountains and will perform better. When I had 37,s and 5.13,s mine was a little high on rpm at 70mph.

No doubt 4.88, 4 dr 37,s auto will drive great.
4dr and 35,s 4.56 is right on.
2dr 35,a 4.10 gears is great

3.6,s dont mind turning, they like it..
Pre 2012 3.8,, 5.13 for a 33 hahaha
 
No expert here but this is how I would be thinking about it. What's your current tire size and your opinion on how it drives on the highway now? That that reference point and the chart below and there's your answer.

upload_2019-5-8_16-36-14.png
 
rcalexander105 said:
No expert here but this is how I would be thinking about it. What's your current tire size and your opinion on how it drives on the highway now? That that reference point and the chart below and there's your answer.

View attachment 292958
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This chart is a 1:1 final ratio chart. With the JK, it is .83:1 with the 5 speed auto. It seems the sweet spot is 2330 rpm @ 70mph a couple charts I looked at put the 4:56 @ 2474 and the 4.88 put is @ 2647.
Thanks for the input so far!
 
4.88s or 5.13s. The 3.6 doesn’t mind RPM. The old school train of though of less RPM the better doesn’t work on a 5500lb+ 4dr JK. Having the engine in its power band helps along with going with a light tire and wheel combo. I’ve noticed heavy ass ATX slabs or others like that sucks the power right out of a JK.
 
Thanks for the info folks. Ordered the 4.88's. As soon as I can save the money for the RCV's, I will get this thing together and on the trails.
 
I am running 4.88's and 35" rubber. On the highway I would rather had 4.56 on trail I am happy with the 4.88..
 
The factory 12 up rubi shafts are really strong, just tack the caps in. I have ran them for years like that and not been easy, never broke one
 
Jason W. said:
Upgrading the rear shafts isnt necessary really either, 32 spline and they are stought.

I would weld the tubes at the housing though, there have been rare cases of tubes twisted in the housing, easy to keep that from happening
Click to expand...

We've had it happen more than once at JJUSA at Uwharrie.
 
Jason W. said:
The factory 12 up rubi shafts are really strong, just tack the caps in. I have ran them for years like that and not been easy, never broke one
Click to expand...
With the 37's, it is just something I do not want to worry about. My goal is to build this once and wheel it. Will probably be my last one unless I luck in to the lottery or something. Oh and I will weld up the rear tubes, great advice. Thanks
 
89wrangler said:
With the 37's, it is just something I do not want to worry about. My goal is to build this once and wheel it. Will probably be my last one unless I luck in to the lottery or something. Oh and I will weld up the rear tubes, great advice. Thanks
Click to expand...

Truss the front then, I learned this the hard way
 
Already have the full truss kit from Barnes. Once I pull the axle, I plan on re-gear, full truss, alloy ball joints, control arm skids, RCV shafts, one ton drag link and tie rod and Long arms with metal cloak joints to attach to the Artec HD crossmember.
 
Wide open design will make an aluminum tie rod for $125 plus the ride
 
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