Novak Conversions Jeep Wrangler TJ engine mounts

42RLE Issue: P0740 TCC Out of Range

NCunlimitedLJ

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Mar 24, 2020
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47
Location
Raleigh, NC
Hey Folks,

Last couple of months the LJ has been pleading for attention by throwing CELs. Started out with a CEL for P0740 (TCC out of Range) and P0841 (Trans Fluid Sensor/Switch A Circuit Range). In one case around the time these CELs came on the trans was refusing to shift into 1st and would start in 2nd, but that was only during one drive and acted fine all other times. Started with the basics like checking trans fluid which had been changed/flushed within the last 20k - that was fine. End up replacing the solenoid pack with a mopar unit and had to replace the harness connector to the solenoid as it was cracked and would not clip in properly. There was no metal in the pan, and what had collected on the magnet in the pan appeared to be normal clutch material. I replaced the trans filter, flushed fluid and filled properly with ATF-4 fluid. That addressed the P0841 error, but around 500 miles later the P0740 CEL came back on.

I have not noticed any drivability issues, shifts fine, but the more I have researched TC issues, I believe some of the shuttering I notice at idle, coming off idle could be indicative of a failing converter. In addition I have noticed a howling/squealing sound coming from the tunnel area at times. I have tried to tell if the TC was locking at highway speeds, but I am not confident I can tell either way.

The Jeep has 155k on it, and I am trying to decide between pulling the trans myself and replacing the TC vs reman/rebuilt. In calling a few shops, of which some seem very reputable and have been around a long time, the consensus is they are not interested in really performing diagnostics and want to do a rebuild or reman unit. I can't blame them at the current mileage, but it pains me a bit to throw money at it, when a rebuild/replacement may not be warranted. I probably put less than 5k miles on the Jeep a year and it does not have to be a DD, which has me thinking of just trying the TC replacement and see where that gets me. If it addresses the issue and I get another 20k out of the transmission, that is a few additional years. On the other side, I am not sure I can handle the disappointment of spending 12 hrs + doing that, only to be crushed when the CEL comes back on.

Curious to get folks' opinions on this, knowing it is not a DD, and I have adequate garage space to leave the Jeep in a state of disrepair for a few weeks while I make time to work on it.


Thanks,
 
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So, if the T/C is failing (or has failed) it can send metal through the transmission, which means you need to at least tear it down and look through it. Plus flush the cooler, lines, etc. When the converter goes, it will make a high pitched whistling sound.
 
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@NCunlimitedLJ The 0740 code leads back to a possible tcm failure which in 05 is thebocm combo behind the battery. The rough idle and shaky mirrors are also caused by the pcm. You can call me at 866-888-7710 to discuss in further detail.

Thanks,

Mark
 
You can send it into us and we can run it in our jeep just to rule out any pcm issues.

Mark - I swapped in my old PCM this afternoon, and it showed similar symptoms. Also I broke out the mechanics stethoscope and clearly isolated the faint screeching/humming to be coming from the transmission. At times this noise can be extremely audible, but during my test session today it was faint and could only be heard from the cabin.

Guessing the torque converter or possibly the trans pump is generating the noise.
 
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I wanted to provide a quick update - against my better judgement, dropped the transmission, replaced the TC, flushed the cooler and lines and reinstalled. Overall the process was not terrible, just finding time to devote to it was a challenge. I definitely learned a lot, and the process of removal was much more time consuming then getting everything reinstalled.

If anyone wants to tackle this, do get a transmission jack - was a huge help. While everything was apart, I also replaced all driveshaft u-joints.

I have approximately 150 miles on it since getting it back together. No more whistling sound that I was audible at idle and low speeds, and I can clearly tell the TC is locking up. I don't want to jinx it, but I think this particular issue is addressed.
 
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Great to hear. Although I’m my experience mounting the trans back up is a much bigger pain than removing it. Replacing the TC itself is an easy job. Actually most everything related to the trans is an easy job, it just requires a TON of effort to get to the point where you can actually do the work.
 
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Novak Conversions Jeep Wrangler TJ engine mounts