4.88 or 5.13 for 2012-16 JKUR on 37s with Manual Tranny

JoeB-JKURX

JoeB-JKURX

New member
I've read on Wayalife (several times) that the 5.13 is recommended with the auto tranny but that a 4.88 would be the right choice with a manual. It, however, wasn't made clear (at least to me) why that is so. On the highway, it doesn't seem like it would make a difference. On the rocks, it would seem that the auto could get by better with the 4.88 because spooling up the torque converter gives the effect of a lower crawl ratio. I'd appreciate it if folks on this forum could explain their rationale for this recommendation.

Thx
 
Pyro1415

Pyro1415

New member
Yeah gear ratios are different. Look up the ratios for the gears inside the automatic and manual transmissions. My guess is the manual is geared a little more tall so you can get away with shorter axle gears. Hope I explained that right.
 
T

TomRalph

New member
notnalc68 said:
Just for reference, man. 5.13 would probably give a ton of power & crawling ability, so I don't disagree.
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I went with 4.88's. Should have it put back together in about 2 weeks I will post up some feedback/results. I didn't want to run high RPM's on the highway :)
 
DWiggles

DWiggles

Caught the Bug
Im waiting on a rear driveline before I swap over to 5.13 in my 3.6, Manual, 37s :thumb:

And I live in FLAT texas, with distance between locations measured in TIME, NOT miles, because "FAR" is relative to speed. I.E. 30 minutes can mean 5 miles, or 50 miles... its still only 30 minutes from here. ;)
 
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JoeB-JKURX

JoeB-JKURX

New member
Far

DWiggles said:
Im waiting on a rear driveline before I swap over to 5.13 in my 3.6, Manual, 37s :thumb:

And I live in FLAT texas, with distance between locations measured in TIME, NOT miles, because "FAR" is relative to speed. I.E. 30 minutes can mean 5 miles, or 50 miles... its still only 30 minutes from here. ;)
Click to expand...

When I lived in Texas, "FAR" meant to run because either the building I was in was on fire or someone was shooting at me.
 
JoeB-JKURX

JoeB-JKURX

New member
TomRalph said:
I went with 4.88's. Should have it put back together in about 2 weeks I will post up some feedback/results. I didn't want to run high RPM's on the highway :)
Click to expand...

Are you running 37s with the manual tranny? My calculation is that the 4.88 with 37s give almost the exact same final drive ratio as the 4.10 with the factory 32s. I have the same misgivings about high RPMs on the highway. I want to get the Centerforce Dual Friction clutch with the heavy flywheel. I figure this will help (keep from stalling) when crawling at very slow speed.
 
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