P0740 code when overdrive is on

[WillT]

I have a jeep TJ 2005 with the 42rle with the p0740 code only when the overdrive on doing 2100 revs on the highway doing 60mph/100kmh but when the overdrive is off and doing 2900 revs doing 60mph/100kmh the engine light doesn’t come on. I have replaced the solenoid pack, replaced the PCM with a wrangler fix, looked through as much wiring as possible and couldn’t fine anything also have added a trans cooler and done a trans fluid flush and changed the filter. Its either I replace the torque convertor with a new refurbished one, don’t use the overdrive button or put some tape over the engine light. What do you Think the problem is.

Cheers Will

 

[Chris]

I have a jeep TJ 2005 with the 42rle with the p0740 code only when the overdrive on doing 2100 revs on the highway doing 60mph/100kmh but when the overdrive is off and doing 2900 revs doing 60mph/100kmh the engine light doesn’t come on. I have replaced the solenoid pack, replaced the PCM with a wrangler fix, looked through as much wiring as possible and couldn’t fine anything also have added a trans cooler and done a trans fluid flush and changed the filter. Its either I replace the torque convertor with a new refurbished one, don’t use the overdrive button or put some tape over the engine light. What do you Think the problem is.

Cheers Will

Given that you've replaced the solenoid pack and PCM, the issue might indeed lie with the torque converter itself.

Since the engine light doesn’t come on when overdrive is off, it suggests that the torque converter is likely not engaging or locking properly when under load. A faulty torque converter could lead to overheating or loss of power, which could explain the code only appearing under certain conditions.

I would personally replace the torque converter with a new one.

 

[hear]

I was pretty sure the TC would lock up in suitable conditions even with the OD off, so that would imply that the TC can lock up, it just doesn't want to in OD for some reason.

 

[jkinner3]

Tire size, gearing? Milage.

 

[jkinner3]

My 06 Rubicon had 33's with stock gearing when I bought it in 2023, it was a dog on road, I was planning on going to stock size tires so
not a big concern, we checked the fluids before the test ride but not after,(would have seen the shavings in the fluid). after taking the body lift off and installing the stock size tires, I took it to my Transmission shop I've used for years for a trans service and it was baked, they ran it hot, so un unplanned rebuild and external trans cooler. live and learn, rebuilt it at 96k milage. It doesn't take much to fry the tourque converter.

 

[hear]

I took it to my Transmission shop ...... unplanned rebuild

What are the odds.

 

[WillT]

Hey guys thanks for your opinions I took it on the highway today and the light came on with the overdrive on but I think the torque converter is the next thing to do.
cheers Will

 

[hear]

Hey guys thanks for your opinions I took it on the highway today and the light came on with the overdrive on but I think the torque converter is the next thing to do.
cheers Will

ON on or off ?

I feel like we had already established it wasn't locking up with the OD on, so what new info did you learn? My question was whether or not it was throwing the CEL with OD off.

EDIT: you answered this in your first post, mah badz

 

[hear]

but when the overdrive is off and doing 2900 revs doing 60mph/100kmh the engine light doesn’t come on.

You haven't said if the TC locks up in this scenario. No CEL means that whatever it's doing is what the computer expected it to be doing. So do you see/feel the ~250 RPM drop after you get to cruising speed with OD off?

EDIT: a quick google tells me that with OD off the TC will lock up almost immediately after the 2-3 shift. I find this a little surprising, but I don't have a ton of 42RLE experience. It's definitely not how the 32RH works. Regardless, if true, it means you might not be able to identify the TC lockup as it may be masked by the 2-3 shift. But the fact that there is no CEL strongly suggests that the mechanicals are working fine.