Needing feedback on RPMs after gears and tires

The BAD Influence

The BAD Influence

Active Member
Going on 5 years since regear and bigger tires. In a conversation with a buddy who has the same gears, 5.13, same Nitto 38s. I used the AEV Procal, he has superchips. At 80 mph I'm at 4000 RPMs, he's at 3100.
I just thought my life is limited to 70 mph. And that's how it's been this hole time. Jeep shifts smoothly, no limp mode, speedo is correct.
Both JKU with 3.6 auto.
Why such a big difference? Anyone with similar build can you provide feedback on your rpms at 80mph.
Thank you
 
Launch said:
Are you sure those aren't 538's in yours?
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Right!!! That crossed my mind. But, if the AEV is programmed for 5.13s wouldn't that cause it to go into limp mode?
Also, the rear R&P went out a couple years ago and 5.13s were put in. If somehow the original gears were mistakenly 5.38s, and then 5.13s put in the rear, all kinds of shit would have happened when I put it in 4x4
 
The BAD Influence said:
Going on 5 years since regear and bigger tires. In a conversation with a buddy who has the same gears, 5.13, same Nitto 38s. I used the AEV Procal, he has superchips. At 80 mph I'm at 4000 RPMs, he's at 3100.
I just thought my life is limited to 70 mph. And that's how it's been this hole time. Jeep shifts smoothly, no limp mode, speedo is correct.
Both JKU with 3.6 auto.
Why such a big difference? Anyone with similar build can you provide feedback on your rpms at 80mph.
Thank you
Click to expand...
both same year and transmission?
 
jeeeep said:
I'd do an actual rotation count / measurement on the driveshaft to confirm the gear ratio, that's a lot of difference
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Yeah when he told me this my brain just couldn’t reconcile it. Instant short circuit. But even if they were 5.38’s… the rpm still wouldn’t be that high. He’d have to be running something in the ball park of a 7.38 which isn’t possible or, programmed for a 28 tire but then his speedometer would be off.
It’s almost like it’s getting stuck in 3rd gear but the indicator is reading 5th.
So
Fucking
Weird.
 
RESURECTIONJK said:
Yeah when he told me this my brain just couldn’t reconcile it. Instant short circuit. But even if they were 5.38’s… the rpm still wouldn’t be that high. He’d have to be running something in the ball park of a 7.38 which isn’t possible or, programmed for a 28 tire but then his speedometer would be off.
It’s almost like it’s getting stuck in 3rd gear but the indicator is reading 5th.
So
Fucking
Weird.
Click to expand...
same tires? if not, swap tires and test
 
RESURECTIONJK said:
Yeah when he told me this my brain just couldn’t reconcile it. Instant short circuit. But even if they were 5.38’s… the rpm still wouldn’t be that high. He’d have to be running something in the ball park of a 7.38 which isn’t possible or, programmed for a 28 tire but then his speedometer would be off.
It’s almost like it’s getting stuck in 3rd gear but the indicator is reading 5th.
So
Fucking
Weird.
Click to expand...
I'll use the AEV to reset to stock settings. Then use jscan to recalibrate. Then, I'll go for a drive and go through the gears manually, and see if there's any difference. If not, I've got nothing.
 
Have the two of you driven together on the road to check each other's speedometers and RPMs?

According to the gear calculator at the Grimm Jeeper website, a Jeep with the W5A580/NAG1 5 speed automatic has an .83 in 5th gear and with true 38" tires, the engine RPM will be 3012 rpms.

It's very possible the Jeep computer is cockeyed. Currently my Rubicon has been reprogrammed to reflect its 4.88 gearing and 35" class tires and the speedometer is off roughly 15 mph at an indicated 80 mph. It appears at an indicated 80, it's actual speed is 65. It's a problem I need to figure out.
 
GP NOIR said:
Have the two of you driven together on the road to check each other's speedometers and RPMs?

According to the gear calculator at the Grimm Jeeper website, a Jeep with the W5A580/NAG1 5 speed automatic has an .83 in 5th gear and with true 38" tires, the engine RPM will be 3012 rpms.

It's very possible the Jeep computer is cockeyed. Currently my Rubicon has been reprogrammed to reflect its 4.88 gearing and 35" class tires and the speedometer is off roughly 15 mph at an indicated 80 mph. It appears at an indicated 80, it's actual speed is 65. It's a problem I need to figure out.
Click to expand...
Using a Garmin GPS is a great way to get an accurate speed to compare with.
 
bobfriesenhahn said:
Using a Garmin GPS is a great way to get an accurate speed to compare with.
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I've tried using the Flashcal app on my phone and the GPS speed function doesn't work. I suspect the aluminum tape I'm using to hold the broken glass on the back of the phone is interfering with the antenna. I'm gonna peel the tape off and try again. Another problem is I fat fingered the buttons on the app and wiped out speedo programming. Speedo was reading zero. I may have to go to the dealer and see if they can fix it.
 
GP NOIR said:
I've tried using the Flashcal app on my phone and the GPS speed function doesn't work. I suspect the aluminum tape I'm using to hold the broken glass on the back of the phone is interfering with the antenna. I'm gonna peel the tape off and try again. Another problem is I fat fingered the buttons on the app and wiped out speedo programming. Speedo was reading zero. I may have to go to the dealer and see if they can fix it.
Click to expand...
disconnect the battery(s) completely and it may reset that
 
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