2014 5sp auto not changing into 5th

[nelston1]

I have a 2014 sr5 hilux 5sp automatic with a 3in exhaust, no chip & no snorkel. Cars done 90,000ks. Just got back from a trip from Perth to Exmouth WA and was having dramas changing into 5th gear. 

Basically I’d be driving in 5th going 110kph, overtake or go up a hill, drop into 4th, and when settling back to 110 the car wouldn’t go back into 5th gear. it  held 4th gear at 3000rpm and the only way I could get it to change into 5th again was to pull over and turn the car on/off again and off I went until I needed to overtake again. 

Seemed to happen only once driving for 4+ hours at a time

 

i have fitted a trans cooler and the have had the trans serviced and taken to Toyota and they have confirmed I have the latest transmission software. 
 

Any ideas ?? Problem was there before and after cooler/servicing etc 

[campbeam]

First thought was to replace the ATF but this was presumably been done recently. Another thought is to also check the ATF level.

Next thought is to check connections for an overdrive/lock button.

Not sure if this is applicable to your transmission but at least it is a few starting points.

[nelston1]

Thanks mate , Correct in the fluid has been changed and tranny flushed. 

 

next step I think is for auto spark to spend some time on all connections and hopefully something pops up