I've got the older 3875, but I know they released a newer version some years after buying mine that was significantly faster in applying the software. It's one of those things though where I've picked a tune and stuck with it, so I don't need the newest one.

For tires and gears, Jscan and a cheap obd2 dongle are a more economical option. The Superchips will read codes and give live data reading, but Jscan is always with you and it's pretty versatile in adjusting other options as well (tire pressure, lights, DRL's, etc).

 

Karl can the Jscan be used on other cars? Like if Im in a friends car and they get a check engine light can I use the same Jscan as my JK? Same OBDII port I would assume? The superchips is Vin locked which is why I asked. I end up needed to read engine codes and clear them on other vehicles more than mine most of the time.

 

I don't recall if it will work in on other vehicles without having the licensees purchased. I bought the 3 pack of licenses and there's only 2 jeeps I check on. For codes, I use Torque Pro with the same obd2 dongle that I use for everything else.

 

OK, so I did have a new thing happen... I was driving home yesterday, holding speed in a 55, OD off, trying to see if it would lock-up the torque converter and after about a mile without any luck I decided to set the cruise. Then it happened, about a second after I set the cruise, the torque converter locked-up. I could roll into the throttle to accelerate a little and the tach and speedo stayed perfectly synchronized. Shortly after that, I turned off the cruise and at that instant the converter unlocked.
So now I know that it is capable, I just have to figure out why it is so unwilling. I feel like, what's holding it back is the low RPMs and relatively high engine load required to maintain speed mainly due to the oversize tires. If I'm right, then when I regear it, this weird behavior should be improved. If I'm wrong, then I guess I'll be looking for a tuner? I don't know what else.

 

Just to reiterate one point made above, those tuners are VIN locked to a specific jeep. When buying used, more than a few people have found that the unit they had been 'assured' was unlocked was still locked to the previous owners vehicle. As a suggestion, much better to make these purchases in person where you can verify. (don't know if this is still the case, but superchips was charging $100 to unlock, if you could prove you bought it)

 

A re-gear will put your RPM's higher at any given speed but that means it won't take near as much to get it moving (low load). The flip side of that is all speeds over 65/70ish you're going to be over 2500rpm depending on your tire size (actual height, not sidewall stamp).

Nthinuf has a valid point- it's been many years bit I bought mine used from eBay and ended up having to ship it back to the original owner to have it unlocked. There's a screen you're looking for it to say when it's plugged into the vehicle but I can't recall the terminology on it. I do know that mine shows the current vin in one of the menus. The phrasing even on a locked one is weird.

 

That's a good post. Make sure it's unlocked vin if you buy it used. I'm not an expert on this but could a rebuild of the tranny fix this issue he is having also? I feel my shift points were so much smoother and snappier once I got the torque converter rebuilt at 170k.

Is really try the superchips before the re-gear. I have 3.73 and 34" tires and I don't ever feel like I need more power or low end off the line. I'm also running a stock front bumper so there is no weight up there.

 

Right now, with the tires and gear I have, at 70 I'm running just under 1900rpm. According to my calculations (1900 * 4.56 / 3.73) 4.56 gears will make that about 2300rpm at the same speed. Also, note this chart that shows 2300rpm to be at the low end of acceptable (green) range and 2600 at the top. I would prefer lower, but if the engine cant make enough power there, it has to turn faster.


Torque converter can make a huge difference, sure, I hope this isn't a deeper transmission issue than that...
That just defies everything I have experienced and read about these Jeeps, and I'm a noob to JKs I'll admit, but you're telling me this superchips makes a 3.8 perform like a V8 and I don't need to regear?? This whole gear ratio thing has had me racking my brain since I bought this Jeep... I did a lot of reading and calculating and finally decided 4.10 just wouldn't be enough of a difference (about 10% higher RPM) and 4.56 should be just about right(about 20% higher). And now that I've made a decision and ordered the parts, I am constantly second guessing that decision...

 

Come drive mine. We'll take the superchips out of it and you can feel the difference. We'll take it on the highway so you can see and feel the RPM's. It'll be slightly different with the manual vs auto but I think it'll be close enough to get the feel for it. The reality is that driving various configurations is the best way to feel/ know the difference. I stared at that chart and read every thread until I was blue in the face, but it's no substitute for seat time.

 

Wow, I really appreciate the offer, if we were 10 or 11 hours closer I would definitely take you up on that! I have a feeling that I would not only be ordering a tuner, but I would be wanting to trade in my automatic for a 6-speed. I think a 2-door manual vs a 4-door auto is a little tough to draw a direct comparison though. JKU is considerably heavier, automatic has more parasitic losses, and top ratio on the manual is 0.84 vs 0.69 for the auto.