First time posting! Just picked up a 2014 JKU lifted with 35" tires.
Thanks JeepLab for all your article, posts and write-ups. I have been following the supercharger article for about 2 weeks now and I'm excited to pick up a Magnuson SC in the next few months. I found your post here very timely as I've been driving around in my new JKU and considering gearing. I have a 4" lift, 35" tires (and as you said, they actually _measure_ 34") and 3.73 gears. As I've driven down the highway at 70 to 75 mph, I have certainly seen that the Jeeps don't handle 6th gear very well there, in fact you are rarely in 6th gear. I can appreciate everyone wanting to re-gear, but as I've read, I had already been coming to the same conclusion as you, people are really messed up about gearing.
For me... I just came from a 2009 Audi A4 with the 2.0T engine (chipped.) That thing was a little rocket at any speed. Here's the thing I find interesting and what I took away from driving that vs. my JKU. Everyone seems to think they are suppose to be able to cruise in 6th gear at highway speeds all the time, and maybe even overtake/pass in that gear. Well, my little rocket of an Audi would cruise in 6th at highway speeds, but when I went to overtake, it dropped down pretty quick to a lower gear (sometimes all the way to 3rd.) 6th gear simply didn't have overtaking power (within reason, it did at 100mph) and that's why the car had 6 gears. That last gear was for economy, and it would drop to 5th in a second to go up a hill. Shoot, now they have 8 gears. Can you imagine an 8 speed JKU and everyone trying to gear for the 8th gear to be able to overtake at highways speeds. Ugh...
I keep reading about people re-gearing a Jeep to try to get 6th gear cruising above 2000 RPM at 70 mph, and I'm thinking, ARE YOU CRAZY!!! Once you gear that high, your screwed, you can't magically drop the RPM's back down to get good gas mileage. However, if you are geared so 6th gear has lower RPMs at highway speed, you can ALWAYS drop down to 5th gear to get the RPM's up. Long story short, I came to the same conclusion you did, be slower to re-gear a Jeep vs. what everyone else is saying. Seems like the majority of the issues with lower RPM's and highway speeds would be resolved with more power (like a supercharger.) At this point, I'm convinced if I do re-gear after getting an SC, I'm not going above 4.11 gearing.
Another case in point... My wife drives a 2013 Ford F350. That has a monster turbo on it that can pump in 40 psi to the engine The other day I was driving at highway speeds and the truck was in sixth gear, and the turbo was registering a constant 4 to 5 psi of boost the entire time on a level highway while the RPM's were down at around 1700 or 1800. Tap the gas slightly and the boost kicked in quick so that it didn't have to drop to 5th gear as quickly, but it still would if you pressed more. My experience with all of my different vehicles over the years has me feeling like I'd rather spend the money on a supercharger and see how 3.73 gears perform with an added extra 100+ hp. I have to assume that the extra 100hp at highway speed with a touch of constant boost like my Ford does will do plenty to help compensate for an RPM range designed for better gas mileage.
Anyway, just my two cents. I'm sure I'll get plenty of comments like "newbie that hasn't driven in the mountains" (I'm from Colorado, BTW, plenty of mountain driving) to "wait until you have the vehicle for more than a week."
Thanks again JeepLab.
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