Hot day/ locks out of overdrive

[mulerose]

My 04 lly, carrying a 2400# camper will down shift and stay in 4th gear 2-5 min. Does it on a flat road for no apparent reason. Speed must be under 70 mph. Quit doing it when weather cooled but put a bra on and problem returned. No codes showen and dealer cannot read any problem. Any ideas? Has been a problem since I owned truck, has 33K miles. I'm so frustrated that I'm thinking of buying a dodge.

[mark45678]

at speeds under 68 mph the trans will down shift to 4th if the throttle position is saying go faster. Now if your only pulling 2300 lbs something is wrong , a stock dmax should not be down shifting to pull that load ! How hot is your trans? when was the last time you serviced the filter / fluid? pulling a 8500 camper thats 11' high and 102" wide at 70 mph I rarely down shift on hills , the lly motor makes it TQ right around 2200 rpm and it drops off quick from there !

[Kennedy]

What size tires? Any other mods like air intake?

Is this in T/H mode or normal mode? Any DTC's set? How many miles on present fuel filter?