I have a 2014 motorhome on a F-53 chassis with V10 and 5 sp trani. Initially when using tow/haul for engine braking on a long downhill, I would allow the engine to go up to 5800 rpm. Last 2 times, when engine reached 4800 rpm, tow/haul would pop off and rpm go to 2000. What is wrong? I cannot find a max allowable rpm listed for my 362hp V10.

 

Welcome to FTE.

What does the owner's manual say about it?

These threads discuss tow/haul. It appears it may "work the same" or have similar properties in all or most models. I realize this is a bunch of stuff to look through, but consider the entertainment value of some of the bickering to be a bonus:

https://www.ford-trucks.com/forums/1...haul-mode.html

https://www.ford-trucks.com/forums/8...haul-mode.html

https://www.ford-trucks.com/forums/9...haul-mode.html

https://www.ford-trucks.com/forums/8...haul-mode.html

Scroll down a bit here. Tow haul makes the trans downshift with an application of the brakes. Multiple applications might be causing an engine overspeed, resulting in an upshift and loss of engine braking, and thus your 2000 rpm engine speed.

https://www.fleet.ford.com/resources...2014_LoRes.pdf

Peak HP is at 4750 RPM, so I don't see this engine being allowed to go over 5500 rpm, but regardless, the engine computer will not allow an overspeed, and apparently will shift the trans to avoid one.

 

Thanks for your reply.
I will spend some time looking at your suggested posts and also plan to have a technician see if any abnormal codes are displayed. I'm just trying to get info prior to my appt.
I understand the computer should prevent over speed but something is wrong if it goes to 5800 initially and now pops off at 4800. Plus 4800 is too low to get good engine braking.