Update for the benefit of the Google searchers.
We no just replace his 42RLE fluid, we do both LJ's. The fluid on mine was lot more redish color than on his, his LJ soak around 5.5 quarts while mine soak around 6.3 quarts. I have to say Wow! my Jeep runs lot more smooth now, His probably it is but he still scare of his tranny will be gave up on Him.
Now, I do install a transmission cooler in-line with the radiator on mine and notice the new temperature sender is just registering 160*. I do assume that I have some kind of loss between the Sender, wire type used and the gauge that may have the reading on the lower side by -/+ 10*.
Are 170* a good operating temperature for this Transmissions?