Any 42RLE experts? The transmission in my 2010 JK is acting up. It shifts great through all the gears except it revs up and misses when shifting down from fourth to third. Otherwise works perfectly fine. No codes. Any ideas as to what it may be?

I’ve rebuilt the valve body including a new solenoid block, VLP solenoid and transducer, and installed a transgo shift kit. I did notice the overdrive accumulator had some wear on both the accumulator and bore. I was hoping the seal expander that comes with shift kit would help, but no luck.

 

How long have you had this JK, and how long ago did it start doing this?

What are the circumstances of this downshift?
Is it when you start to climb a grade on the highway? On slower roads? Or both? Is cruise control on, or off?
You mentioned a miss. You mean the engine misses when it revs up?

 

I have had this JK for a month or so, I bought it knowing it had transmission issues I'm just trying to figure out if there is a fix before rebuilding it. The downshift is like a slipshift where the jeep goes to shift down from fourth to third and the rpms spike at 4500-5000 rpm momentarily and it will then drop into gear rather abruptly. This happens when the jeep shifts from 4th to third while under load such as going up a hill, or trying to accelerate. If you are slowing down the shift is unnoticeable.

 

It has been my experience with the 42RLE that the computer waits too long to downshift from O/D to 3rd when going up a hill, especially at highway speeds.
By the time it wants to make the downshift, it's too late for third, and it momentarily goes to second, with the accompanying high RPMs.

You may have transmission problems, but...
Try this: As you approach the bottom of the hill, hit the O/D Off button. It will go into 3rd before the computer has a chance to wait too long. Hit it again at the top of the hill.
See if the downshift is more like it should be.

I keep mine out of O/D when at 55 mph and less. I use the technique above when on the interstate.