42RLE torque converter clutch noise after service

Hey fellas,
I’ve got an issue I’m chasing. I recently had a failed solenoid pack, so I replaced it (new filter and fluid obviously). After reassembly I filled it with fresh fluid — Penrite ATF FS full synthetic multi-vehicle, as it’s listed as suitable for Chrysler ATF+4.
Since then I’ve been getting a chugging / shuddering noise that sounds like the torque converter clutch can’t maintain stable friction, especially at steady cruise. From what I can tell, the fluid is likely the issue.
I’ve now ordered Petronas ATF+4 to correct it. Just wanting to confirm I’m on the right track and see if anyone has any tips or advice — this is my first Jeep project.
Cheers.

hear said:

If you used only ATF+4 I would not expect the brand to give you any different results. I've used "name brand" and I've used Oreilly brand, walmart brand, and tons of it.

If you used anything other than pure ATF+4, I would love to hear feedback because I would expect problems. Multi-vehicle anything is a marketing way of saying "it looks like the thing you need but probably won't work in your car but we're happy to collect your money and there is a non-zero chance it will work if for no other reason than that the universe is non-deterministic at small enough scales and large enough energies. Who are we to say what will or won't work? Don't @ us."

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Yes, that aligns with what I suspected. I used a multi-vehicle ATF because it explicitly states compatibility with Chrysler ATF+3 and ATF+4 specifications, so on paper it should have been acceptable. In Australia, genuine ATF+4 isn’t readily available off the shelf and usually has to be special-ordered.
That said, the 42RLE appears to be particularly sensitive to fluid characteristics, especially with torque-converter clutch operation. My hope is that replacing the fluid with a true ATF+4 via a pan drop and refill will allow it to dominate the remaining multi-vehicle fluid without needing a full flush. With some luck, that should resolve the TCC shudder.
I appreciate the guidance. Accurate information on this transmission is hard to come by locally in wa.

The only change after the transmission work was the use of a multi-vehicle ATF. Since the 42RLE seems to be a bit particular about fluid friction characteristics, especially with TCC operation, I’m going to swap back to a true ATF+4 as a starting point and see how it behaves.
I’m keeping the PCM possibility in mind, but they don’t usually fail in isolation without other symptoms. It seems sensible to rule out the simple variable first. The correct fluid should be here by the end of next week, and I’ll report back if the issue persists and reach out to the person you recommended. Appreciate the help.

Unique Username said:

I doubt just changing the fluid will make any difference. ATF+4 is not going to break down as easy and will handle the day to day operation but a lesser AFT can make the transmission perform fine for a short time. I would suspect you have other issues and would consider you likely have other issues. Likely a failing PCM. Maybe hit up @Wranglerfix before tossing money at it. He would be the person who has a good understand of the operation on the 42RLE in terms of performance issues in operation.
ATF has done the job to move 42RLE down the road many of times when +4 was not available.

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RS Hill said:

As Unique User name says, the PCM is a possibility as well, that is some that escaped my mind.

The fluid side sometimes takes a bit to get the incorrect fluid out. If you had a drain plug, I would say do a couple drain and fills. Otherwise it’s the messy option by dropping the pan. No promises that this is the ticket but it seems closely tied from a time perspective.

I hope this get to the bottom of it for you.

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Cheers. Once the ATF+4 arrives, I’ll swap it over and report back with the result at the end of the week.