Worse MPG after re-gear. Any soloutions?

You can’t change the shift points of the 42RLE with HPTuners. That’s what Ryan at FRP told me.

Maybe something changed?

Could be, HP is updating things all the time. It is worth noting you must have purchased the additional credit for the TCM to flash it. Also may have to do with the difference between the MPVI and the MPVI2. Probably worth more discussion in another thread.
 
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I have been using the HP tuner on 2005/2006 wranglers since HP came out with the Jeep tune, as Jezza and psrivats noted the shift points can be adjusted, just understand the speed shown in the table are based on output shaft speed not engine rpm.
 
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I have been using the HP tuner on 2005/2006 wranglers since HP came out with the Jeep tune, as Jezza and psrivats noted the shift points can be adjusted, just understand the speed shown in the table are based on output shaft speed not engine rpm.

I figured that out after the second flash. Even though HP has it labeled as Engine RPM.
 
I figured that out after the second flash. Even though HP has it labeled as Engine RPM.

I assume the rpm listed must be at a given throttle percentage and then its scaled accordingly so the shift point increases with more throttle?

Unrelated to that, but it seems like that could be really easy to screw up if they didn't put any safety logic in to prevent it. Like say you accidentally put some overlap into the downshift point of one gear and the upshift point for the gear below it so that it could get into a chatter that downshifts and immediately upshifts and repeats until you've accelerated or decelerated out of it.
 
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I wouldn't expect mileage to change much on either side with an axle re-gear. Only improvement to expect is in the driveability.

When was the last time you checked your O2 sensors?

Never. I figured they would throw a code. I guess they could just happen to go out exactly the same time I did an axel swap.
 
fwiw, I get about 13 with 35s, 4.88 and an AX15. 12 seems pretty awful for 31s.

How many miles have you put on it since the regear? I have to wonder if the gears were set up way too tight, but if that's the case I would expect them to eat themselves and be noisy in short order. When my first set of gears ate themselves in 2000 miles, the guy that set the new ones swore I would feel a difference in acceleration because of how poorly the first set had been done. I did, but it was hard to say it was a better setup or the fact that I also went from 4.56 to 4.88.

Yeah, they had to do them twice. First set didn't mesh right or something. Made a hum. They pulled everything apart and redid them. It drives really nice now. I've put on about 3,000 ish miles since the redo.
 
My 42RLE never "hunted" between 3rd and 4th, it was damned hard to even get it out of 4th (Overdrive) once it was in it. You had to stomp on the gas hard to get it out of 4th or turn the OD off.

Mine was the same way until I tuned it with HP. I used to push the OD switch to get it to kick down. After the tune it drives much better.

I've got a FRP tune on the way. Hopefully that helps some too. You have to push the pedal to the floor to get it to downshift into 3rd
 
Something is wrong somewhere. I was getting 16.5 MPG with 33's and 5:13 gears, and now same gears and 37's is still getting 14mpg. Granted I live in a relatively flat area but 12 MPG on 31's is ridiculous. My Armada on 32's gets 14 MPG and it's a V8 full size 3 row SUV.

I agree with above, check and see if your brakes are dragging, or if you've got drive line bind somewhere.

Yeah, that was kind of my thought as well. I may bug the shop again, though this is sort of a hard thing to just be like "It is not right.". I'll give the brakes a look. I assume just grabbing the driveshaft and giving it a twist to see if it has the small amount of play it should is enough for a driveline "bind" check?
 
Yeah, that was kind of my thought as well. I may bug the shop again, though this is sort of a hard thing to just be like "It is not right.". I'll give the brakes a look. I assume just grabbing the driveshaft and giving it a twist to see if it has the small amount of play it should is enough for a driveline "bind" check?

Take a nice long drive at highway speeds at least a mile or two and then pull over somewhere safe and feel the face of all the rims where the lug nuts are. If any of them are warmer at the center than they are out by the tire then your brakes arent releasing all the way. Driveline bind will be more of a vibration that you feel get worse the faster you go.
 
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Update: I jacked up the Jeep, and spun all the tires. The back tires spin easy and keep going like a merry go round after you stop pushing them. The front ones do not though. It is more work to get them spinning, and they almost stop right away. I don't think the brakes are dragging, but I guess they wouldn't make noise necessarily. I tried them both in 2h, and 4h. What are some things to look for up front that might be giving that extra resistance? I'll also try a long drive and feeling the brakes, and if they are warm/hot.
 
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Update: I jacked up the Jeep, and spun all the tires. The back tires spin easy and keep going like a merry go round after you stop pushing them. The front ones do not though. It is more work to get them spinning, and they almost stop right away. I don't think the brakes are dragging, but I guess they wouldn't make noise necessarily. I tried them both in 2h, and 4h. What are some things to look for up front that might be giving that extra resistance? I'll also try a long drive and feeling the brakes, and if they are warm/hot.

The rear will spin more freely than the front because of the disc's. Brakes are not likely the culprit here.
 
Update: I jacked up the Jeep, and spun all the tires. The back tires spin easy and keep going like a merry go round after you stop pushing them.

Do you have rear drums? If so, the tires shouldn't spin that freely. There should be a slight drag. Your rear brakes need to be adjusted.