Did you go to 4.88s because you live at altitude? From everything i’ve watched, read, or heard, that set up is above average for 315s
Yes and yes. I was stuck obsessing between 4.56 and 4.88's. I talked to several shops and after I described what kind of driving I do; Colorado high altitude trails, possibly some day an overlanding trailer, and the (remote) possibility of going to 37's down the road - and not wanting to re-gear twice - 4.88's were the overwhelming recommendation.
Thanks Kyle. I'm all about performance and reliability on and off road. I'm sitting with a 2dr stock Rubicon 3.6L auto w/that I am moving to a 1.5in Clayton Overland Plus lift w/315 KO2s by years end.
This right here is the biggest factor in my opinion why some recommend gears that are too deep for my use. I live 3 miles off of I-5 where EVERYONE is cruising at 80mph+. The jeep sees 85mph almost every time I drive it, and on a road trip to Moab or Telluride it will be required to sustain that speed for 14+ hours. Our roadtrip to Alabama last may with 5.38's and 38's solidified my opinion that our Jeep was better off without deep gears. Even the 4.56's in the XR have me wanting to go to 37's soon to get the freeway rpms where I want them. If you never drive above 70mph, there's no penalty for going LOW. If you set your cruise control at 85mph to keep up with the semis out in AZ, UT, NV, etc you may very well regret going too low.
Do your rpm’s get too high when you go faster on the freeway than you normally do? or is it still comfortable
Out of sheer morbid curiosity, how many RPMs are you turning at 80 and 85? In both 7th and 8th?
2300ish at 80 and just under 2500 at 85 if I recall correctly. That's with 35's and 4.56. If I went with 4.88's like some suggest for 35's I'd be pushing ~2700 at normal freeway cruising speed for me. That's just too damn high for me to want to run for hours, especially under low load conditions like the ~20 mile downhill stretch coming home from Las vegas/UT/CO just east of baker. Hard pass.
RPM's in 6th are comfortable. Engine is happy, good acceleration. This isn't a scenario I find myself in the Jeep too often; flat-cruising freeway @ 75-80mph. But when I need to do it, it's perfectly fine.
If you’re trading your Jeep in get the 4.88 gear set for 35’s on the 6 speed and 4.56 on the auto. That’s the recommend gearing from Jeep. I’m planning 4.88 on my Jeep with the current 35’s and the possibility of jumping to 37’s on the next set of tires.
At 85, which is not "normal highway speed" in most states except WY and MT, I am turning between 2700 and 2750.
I'm not sure about where you come from, but 5-10 mph over the posted speed limit is normal freeway speed everywhere I've ever lived? So much so that a highway patrol sitting on the side of the road with the radar gun out the window won't budge if you're that close to the limit. Posted speed limits all over the west...75-80. You'll literally have semis pulling triples passing you in AZ if you're under 80mph. Even if you're trying to save fuel you can just draft one of them and still roll 80. On the east coast where you don't have straights that are dozens of miles long and you'd travel through 6 states before I can get out of CA in the same distance 80 might be rare. Here it is bellow average unless you are in the bay area, LA, or Sacramento. As far as mundane performance, the 5.38's made the jeep a half second slower 0-60 than it was with 4.10s, and that was still 7.5s which is hardly mundane for a 5k+lb vehicle on 38x13.50's if you ask me, but it's more mundane than the 7s flat it would do with 4.10s. I'd call cruising on the wide open freeway at 70 while everyone and their mom flies by mundane, but to each his own.
