WOT won't shift Please Help!

Studfam24

Studfam24

New member
Just a week ago our 16' JKUR began having an issue. While attempting to pass a vehicle at WOT it would not shift and instead held 5500 rpm until I let off the throttle. Also it felt as if it were slipping or cutting power. It would not gain speed as soon as it hit this rpm no matter the gear we were in or if we moved it to manual shift mode.
She is on 37's and has been for over a year without issue. Only 28k miles on the automatic and is daily driven by my wife.
We took it into the dealer whom told us it was the tires that were the problem but if that were the case they would have caused the issue to begin a year ago. I obviously objected to this statement and explained how many thousands of Jeeps run a 37 without issue and clearly there was a problem. They said they cannot fix the Jeep if there was no DTC's showing. He Mechanic agreed there was an issue but couldn't confirm what it was. They agreed to keep looking into it.
Today we received a call stating they put factory tires on it and it no longer has the problem. I didn't believe them and I am making them reproduce this tomorrow for us.

Does anyone have any insight to this problem? We have had numerous Jeeps in the past and we build our rigs with quality parts.
Currently it sits on a factory drivetrain/powertrain still as we didn't want to void the warranty.
It had an Evo bolt on coilover kit which we love. 17" Kmc Machetes, and 37" stt pro's.
Any help would be great. Thx so much.

Cheers!


Build thread:
http://wayalife.com/showthread.php?t=37388

IG @jk_studcon
 
Frydaddy

Frydaddy

New member
First thing is to reprogram that tire size into the computer. Superchips Flashcal, or AEV Procal can do it.

Next step is to regear it. 37s on 4.10:1 isn't really the best. You might need 4.88 to return to stock ratios.
 
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Studfam24

Studfam24

New member
We removed the speed cal just to make sure that wasn't the issue and it replicated the issue both ways.
I thought of that as well but why is the issue arising now and not when we installed the tired initially. It shifted great for over a year with 4:10's.
Wouldn't the issue persist at all rpm ranges if it were the gears?


Build thread:
http://wayalife.com/showthread.php?t=37388

IG @jk_studcon
 
AZ Explorer

AZ Explorer

Caught the Bug
The thing is, it isn't shifting as great as you think. I dropped mine into manual to experiment when I was in the mountains or passing with high rpms to see where I was at. The transmission was in 2nd gear at 75 mph to move it at all. You're using the hell out of the lower gears of the transmission way more than normal. The computer is not using the upper gears much, if at all, and could cause premature wear on the trans. After I geared up, I was in 4th and 5th in the same situations and that is where the it is designed to be. I went with 5.13's for my 37's and have been happy ever since in the mountains or the flats.
 
cozdude

cozdude

Guy with a Red 2-Door
The main thing I would look at is your trans fluid level and the condition of it. With the larger tires your putting more stress on it which will heat it up quicker and break the fluid down faster. Pull the dipstick and see how it smells. If it's burnt smelling then drop the pan and get new mopar fluid in it. If it doesn't smell burnt but is blackish then change it as well. Put a new filter in on both occasions.
 
aTX427

aTX427

New member
I agree with the others, and double check your calibration. I also wouldn't necessarily recommend floor boarding it regularly with otherwise stock components and 37's. It's way more stress on the driveline.


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Studfam24

Studfam24

New member
cozdude said:
The main thing I would look at is your trans fluid level and the condition of it. With the larger tires your putting more stress on it which will heat it up quicker and break the fluid down faster. Pull the dipstick and see how it smells. If it's burnt smelling then drop the pan and get new mopar fluid in it. If it doesn't smell burnt but is blackish then change it as well. Put a new filter in on both occasions.
Click to expand...

Good advice, the fluid looks great but now that I think of it, I haven't floored it since I've had the fluid changed at the dealer a couple months ago. Wonder what they got into. [emoji15]


Build thread:
http://wayalife.com/showthread.php?t=37388

IG @jk_studcon
 
cozdude

cozdude

Guy with a Red 2-Door
Studfam24 said:
Good advice, the fluid looks great but now that I think of it, I haven't floored it since I've had the fluid changed at the dealer a couple months ago. Wonder what they got into. [emoji15]


Build thread:
http://wayalife.com/showthread.php?t=37388

IG @jk_studcon
Click to expand...

Well it could be that they didn't fill it right. Your suppose to fill it while on level ground, shift thru all the gears (all forward, neutral, and reverse), and check the level with the trans up at operating temp and running. If they didn't do this you could be a quart or two low when at temp.
 
PT1400

PT1400

New member
Most likely the torque converter. Regardless of the speed calibrators being changed, a "slipping" feeling like a worn clutch is going to come down to the torque converter. Even burnt fluid will shift gears. Burnt fluid will burn up the torque converter a hell of a lot quicker than the gears. If you're going to run big tires, either order the rig with the correct gears or regear it when you get those tires put on.
 
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