Stays in 5th and 4th gear way too long

On the stock tune, cruise control is miserable. I couldn’t believe how bad it was when I first purchased my truck.

Running the current kdmax tune, constant speed cc is much improved but still could be better. It’s the one thing on the tune that’s still not what you’d expect from the factory.

I never use radar ready cc, so can’t comment on how well it works with the tune.

 

I think what most of us are telling you is: there isn't anything for the dealer to "fix". The truck is doing what it needs to do to keep going the speed you've asked it to go. It's a high revving engine with the bulk of it's power way up in the RPM range and a truck with the aerodynamics of a brick. The engine noise at high revs may sound disconcerting to you, but it's what the truck is programmed to do.

Options to alleviate some of this distress have already been mentioned:

1. Tune it
2. Re-gear your differentials
3. Turn off the cruise control and use your right foot
4. Slow down
5. S-Mode

 

If you have cruise control on, and it gets "stuck" in 4th gear, lightly apply pressure to the gas pedal until it drops into 5th. It seems counter-intuitive, but it works.

 

Get stuck in 4th (sometimes in 3rd on the hills) is "normal" across all 3rd gen years at high speeds and engine loads. it has to do with ACIS system being ON at those moments.
FYI, various tunes have the same issue.
To overcome it, use upshift in S mode.
first of all being stuck in 5th is not that bad.

If you are getting stuck in 5th in D, you need to check if ACIS is on. ACIS activates at 2600 rpms. Also need to know how much throttle you have during the event.
In my experience, I couldn't reach 2500 rpms on stoke "tunning", the tranny would downshift to 4th due to reaching max engine load or the downshift point.

On some tunes, you can hold 5th in D based on throttle input.
As I said, get a phone based obd2 app. It will help you understand and troubleshoot the issue.
Then you can go with software or hardware options to correct those issues.
If all this happens while using Cruise control, I wouldn't worry about. It is "normal".

 

KDMaxx tune

 

there is a TSB for the trans . I complained that my truck suffered from all the symptoms. the TSB was performed for only that reason. Then I got a tune. https://www.tacomaworld.com/threads/tsb-0092-20-is-awesome.696230/

 

If it goes into 5th or 6th, and receives enough load to call for a downshift, it will. If it doesnt have enough load, it will upshift. The truck is geared in the axles, and transmission incorrectly, and cause issues for some drivers. This is why you hear many people complaining of the "shift dance". The 6 speed auto has 2 overdrive gears, 5th and 6th. The truck truly hates to be in 5th or 6th under 2200 rpms. The truck wants to live at 28-3300 but, the shift logic, and the driver wont allow it. So you get the constant shifting up, down, etc... ad nauseum. Be careful what you wish for, If they "fix" this, you will be here in a few days, complaining, why does my truck constantly shift up and down, even on flat roads between 50-65 mph. If I could wave a magic wand, I would have the truck never shift up from 4th gear below 50 mph, up from 5th below 60-65, and when in 6th above 65 mph, not to shift down without a major load, or losing 10-12 mph via cruise. End the shift dance. The truck really doesnt need a 6th gear, second overdrive. Ski

 

Stop being scared, you aren’t damaging anything. The truck doesn’t care at all if it sits at 3000rpm all day driving down the road.

 

You accidentally explained why I have a Manual Transmission. My shifting algorithm is quite good, I anticipate inclines and upshift before it is necessary.

 

Tune time

 

count your blessings, the truck has learned not to shift up just to immediately shift back down. Since adding weight and a lift my truck has learned to hold gears longer and instead of shifting to 6th and having to downshift to 5th at the slightest incline or increase in speed it will hold 5th or 4th depending upon the speed and keep it in the powerband of the engine. Don't worry about it.

 

Mine will only sit in 6th in ideal conditions, being below 65, flat, no head wind. Seems like the wind resistance is enough above 65 to require 5th gear most of the time.