Trans shifting ? on 5.4L, 2003

[Kistler]

Using cruise control (I lock-out OD by pushing the button) while towing, I notice that cruising at 68 mph on some grades the vehicle does slow to about 58-60 sometimes, the trans shifts to 2nd or whatever that is just below top gear without OD and the cruise control "gives up" sometimes.

Is something wrong here? Besides cruise control giving up I have also noticed that sometimes the trans doesn't wish to shift back to 3rd gear on it's own. Having achieved 68 mph or whatever it just stays in 2nd. This has only happened twice. I was on I-40 east of Albuquerque-west of Santa Rosa and it was HOT.

 

[monsta]

The CC will "give up" after it loses "X" mph. I do no tknow the exact number.

The "gear" below OD is actually the torque converter unlocking (when downshifting) and locking (when upshifting).

It may stay in 2nd due to the gas pedal position and not necessarily the speed attained.

How much does the trailer weigh?

 

[Kistler]

My trailer weighs about 7,350 lbs. loaded. I only carry 1/3 tank fresh water and the holding tanks are empty; this is the way I was loaded when I weighed.

Thank you for the reply, by the way.

Kistler