I found this thread but its 4 yrs old now.
https://acurazine.com/forums/showthr...n+hunting+gear

My 04 has the same issue. I replaced the pressure sensors on the trans and fluid change to redline racing type f. It still hunts between 4th and 5th trying to figure out which gear it wants. The trans doesnt seem to have any other issues and shifts smooth. The only code its ever thrown was for the 02 sensor bank 1 running lean. It has only thrown that code one time and the car started hunting after it lit the code. But, it was doing that from time to time before it threw the code as well.

It seems that its a app sensor issue or something engine related instead of trans related. I replaced the app sensor after it continually was in limp mode about 20k miles ago and that instantly fixed my limp mode issue.

 

Does it do this when you're just cruising steady state down the highway without changing throttle position?

Are you sure the trans is actually shifting between 4th and 5th or could it be the torque converter clutch (TCC) locking and unlocking? Try putting it into manual 4th or 5th gear and see if it still does this.

When the rpms come up, does it try and accelerate, decelerate, or stay at the same speed? This will help in figuring out if it's the APP sensor or not.

 

No acceleration, same speed.

What would be the cause of the trans locking and unlocking?
Thanks

 

It could be several things. Vehicle speed sensor, any of the various speed sensors on the trans. Bad trans temp or engine temp sensor. It's most likely not a mechanical issue but you never know.

Have you tried holding it manually in gear to see if it still does it?

 

I had more time to read up on the 4th 5th rpm's possible being in the wrong range but since mine never did this for the first 85k miles and I have 90k on it now it seems there is some other issue. I am leaning towards the app sensor since I've replaced it once allready and also becuase it's on national backorder recently. I understand thats not a diagnoses but points me where to start looking. I need to research and find out what voltages are supposed to be for the sensor. I remember checking tps sensors for voltage and it being very easy to determine if they were good/bad with a voltmeter. Hoping this is as easy.

My limp mode issue took forever to throw a code, like years if I remember correctly. Another interesting thing on my car was if I gunned the throttle to redline it would flash the check engine light but show no code on my scan tool. I thought that was a bad crank sensor but not sure. That doesnt happen anymore becuase I don't really drive like that but did when I was learning how the car responded after we first bought it.

I'm also not ruling out vacuum or possible even bad/corroded grounding. Our cables on this car are pretty lame.

 

It seems I cant reproduce it in manual but I need to make sure. I do know that if I'm in 4th manual it wont happen. But i never really put it in 5th manual because the rpms are to low and with the notorious 5th drone and xlr8 mounts it is pretty annoying.

 

Manual 5th it still bounces. 4th no bounce.