[Jake3339]

I am wondering what gears I should run with 37 inch ko2s. I have a front prorock 44 and rear high pinion prorock 60. I am trying to determine what gears I should run due to the rear 60 running on the coast side. I honestly don't know if just because it has a larger diameter ring gear it is necessarily stronger than the stock rear 44 r&p. I also don't want to make my gears the weakest link. Does anybody have any input or real experience on this set up?

 

[Jester1492]

I've been told 37" tires are happiest in the range of 4.88 gears. If you plan to do a bunch of towing at elevation than 5.13s might be a better choice.

 

[HKLover]

I have 37's, auto trans, and 5.13's. My Jeep is a 4 door and heavy with steel skid, bumpers, etc and I also have a fridge on a slide out in the rear cargo area along with some 6" drawers, and I would have regretted going with 4.88's.

I think the BFG KO2's run small for a 37 and are much lighter than the Nitto Trail Grapplers I am running.

 

[Ballistik_monkey]

I also have 5.13s with an auto. 4 door, steel bumpers, skids, etc. i personally LOVE the ratio. I can understand the highway guys complaining (rpms at 70 or above are pretty high), but for me...I just dont drive fast on the highway...take my time and tootle along. for city driving, it is awesome.

 

[rockred]

It all depends upon a variety of factors. If you are quite heavy and intend upon towing with no consideration for highway speeds above 65 MPH, 5:13 would be your cup of tea. Problem with 5:13 is the teeth on the gears are getting quite small and serious rock crawling might be contraindicated. Currently I am running 4:56 with 37 inch tires. Fine for a very heavy 2013 JKR [automatic tranny] with lots of modifications. Sucks if I tow anything. I was running 35 inch tires when I did the gear change. I wanted the same gearing ratio with stock so I went with the 4:56. Right now I have plenty of freeway speed.... 80MPH if desired. I must admit my gas mileage sucks. I do plan on going back to 35 inch tires....getting difficult for my wife and I to climb into the Jeep and we are pretty much done with the serious rock crawling!

 

[IndyRubicon17]

I've been on 35's with both 4.56 and 5.13 and on 37' with both....you want 5.13 all day long....4.56 sucked with 37's... My boy did 4.88 on his and wishes he did 5.13....we both have very similar modded 2 doors that are armored and heavy...he is actually doing the stretch to his jk right now....jeep works or something so it's only getting heavier....

 

[harpersJK]

I also have 5.13's and love it. I've got a heavy overland rig running 37's on currie 44/60 combo. Gas mileage around town is around 12 and I've actually got 15 to 16 out on the open road. As for highway speeds, I usually keep it under 70.

Around town the acceleration is great for a heavy JKU.

 

[Lloydrage]

I run 5.13 with my 37s and suggest the same for JKs with auto trannys.

 

[Doc222]

seen high pin rear explode. but to be fair they run 40s too. i wonder how well they wear for street use? cost side tends to create friction you wont see if ran on the right side.

37s can do well on d44s. the main point that tends to fail will be the front long side axle shaft ujoint. No matter what shafts excepting m300RCVs. i our club we seen the regular RCv not fair so well. But i have seen i real life just a week ago friend snapped the stub shaft of a M300. But again to be fair the nest buggy in same gate keeper blew a d60 same spot. at that point the rest of use tossed in the towel and it became a recovery day anyway. trail had a huge rain and it went from hard to buggy hard.

So for me i carry front axles as parts and rears, but i have a mig welder as well and a lot of other junk aboard. run g2 shafts in 5 years i think have blew a ujoint. But that was in a bad bind and should have winched out. I have had to loan out axles on the trail a number of times. Luck for them i was there.........nothing worse then being on a hard trail that 37s locked to get in and brake down half way where a 3x4 will not do and tends to just bust more stuff. seen that too. the brake a front then keep trying to then brake the other side. now its a 2x4 and it can only get worse.

But use will play out how well any jeep holds up. why go 37s locked to run moderate trails? trouble is those trails will beat a jeep up. dents and rock rash. replacing junk all the time when it goes fubar. Fixing other junk when they do..its part of the fun.

i been looking for a buggy and one here i liked alot but it has a high pin rear on that has a fabricated rear too on 43"......i would drop it to 40s but i know in the end i will bust the high pin. For what he wants for the rig i would end up needing say a 14b to add in toe the 30k he wants...20k i would be on that and just change rears after it busts up. but its a real nice buggy cj7, very nice. done by a pro shop at one time. must have cost a ton to do. I would rather rebuild something like that then try to buggy a JK. Ls3 in it as well, atlas coil over 4 link......

4.88-5.13 not much change in strengths here. not like comparing say 3.21 to 5.13, now you see a huge change in pinion side. its the being run on the coast side that makes them what to separate in load. they tend to have 1 or 2 load bolts to keep that from happening to much..

 

[BlueBabySound]

IMO
2 door = 4.88
4 door = 5.13

I would not worry about 5.13 on a D60.
We run a 44/60 on our 2 door with 4.88 gears/37" tires, no issues (other than a seal) in the 75,000 miles we've put on it.

 

[NoWhiningX]

I run fully armored 4 door Rubicon on 37s with a 4 inch lift, winch, dual air compressors etc. Tires are Cooper Discoverer Pro (run right at 37 inch). 4.88s seem to work well for me. Either ratio will work fine I'm sure.
no whining now...

 

[Peteyur]

I have 37's, auto trans, and 5.13's. My Jeep is a 4 door and heavy with steel skid, bumpers, etc and I also have a fridge on a slide out in the rear cargo area along with some 6" drawers, and I would have regretted going with 4.88's.

I think the BFG KO2's run small for a 37 and are much lighter than the Nitto Trail Grapplers I am running.

I am in the same predicament about which gears to buy? My jeep is a 2016 Rubicon with a 3.6 and auto trans. I am running 37 inch STT pros in the jeep was supposed to be just a wheeling jeep here in northern Michigan. However, I do wanna run it on 4 to 6 Hour Rd. trips up to the UP to wheel also. I can’t seem to land on either 488 or 513s.
If you don’t mind, what are you running for RPMs at 70 or 75 miles an hour?

 

[TerryC6]

I am in the same predicament about which gears to buy? My jeep is a 2016 Rubicon with a 3.6 and auto trans. I am running 37 inch STT pros in the jeep was supposed to be just a wheeling jeep here in northern Michigan. However, I do wanna run it on 4 to 6 Hour Rd. trips up to the UP to wheel also. I can’t seem to land on either 488 or 513s.
If you don’t mind, what are you running for RPMs at 70 or 75 miles an hour?

4.88 approx. 2600 rpms, 2730 for 5.13 at 70 mph.

 

[Lloydrage]

I’m 5.13 with 37” SST pros. My 3.6L with auto trans does shifts often when I’m going 75-80. But I drive to Moab every year and it’s fine.

the 5.13 is amazing rock crawling. It literally crawls on its own.

 

[Peteyur]

Thank you both for your help and info. I have ordered the 513 gears and can’t wait to put them in.

 

[HKLover]

I am in the same predicament about which gears to buy? My jeep is a 2016 Rubicon with a 3.6 and auto trans. I am running 37 inch STT pros in the jeep was supposed to be just a wheeling jeep here in northern Michigan. However, I do wanna run it on 4 to 6 Hour Rd. trips up to the UP to wheel also. I can’t seem to land on either 488 or 513s.
If you don’t mind, what are you running for RPMs at 70 or 75 miles an hour?

I'm running right around 2700-ish at 70 IIRC. I run 75 without any issues except for gas mileage taking a big dump. But, I didn't buy a Jeep for its gas mileage.

Edit to add: You will be really glad you went with the 5.13 over the 4.88 I think.

Good luck with your build.

 

[Iron Bender]

4.88 approx. 2600 rpms, 2730 for 5.13 at 70 mph.

Are those real world RPMs or chart RPMs?

 

[TerryC6]

Are those real world RPMs or chart RPMs?

Calculated. Exact tire diameter which will vary between different brand of tires.

Engine RPM / Engine Speed Calculator

Crawlpedia's RPM and Engine Speed Calculator will find your engine RPM at any speed given your transmission ratio, ring and pinion gear ratios, and vehicle speed.

www.crawlpedia.com

 

[Iron Bender]

Calculated. Exact tire diameter which will vary between different brand of tires.

Engine RPM / Engine Speed Calculator

Crawlpedia's RPM and Engine Speed Calculator will find your engine RPM at any speed given your transmission ratio, ring and pinion gear ratios, and vehicle speed.

www.crawlpedia.com

Manual vs auto changes things, too. That’s why I am always curious what people’s actual RPMs are.

 

[TerryC6]

It is going to vary. Tire size vary as much as an inch. All the gear ratio's are all published. What my rpm is and what some else's is will be different. One inch difference is worth about 80 rpms. Difference between gears (diff) is about 130 rpms. Plug the numbers in to get your answers.