How to force truck to downshift while towing? - Ford Powerstroke Diesel Forum
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post #1 of 2 Old 08-23-2019, 05:58 AM Thread Starter
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How to force truck to downshift while towing?

So here's my situation, I have an 08 6.4l CC SB 4x4 auto 5R110W. The only modifications are the DPF-R+ 70hp tune with only the dpf/cat deleted. EGR still in place; still stock suspension and tire size. I tow an 8k lb 30ft camper trailer alot in the summer. I normally tow at 70 mpg on the highways, but do a lot of mountain passes in utah and idaho. I use the tow/haul button every time.

My problem is, when going up long, steep grade passes, my speed may bog down to 50-55mph or so, but no matter how hard I push the accelerator, it will not downshift. I don't mind slowing speed for these passes, but sometimes I've really needed to speed up to pass a semi or something and I cannot get it to downshift for the life of me. I'm getting plenty of boost when I bog down speed (almost 40psi at times), but the rpm's are just too low, 1500rpm or so. So how do you force a downshift? Do you shift down from 'drive' to '3' on the column shifter? Going down to third gear seems like it would be too drastic. What would happen if you disengaged tow/haul, would it downshift easier then?

I'm used to my old 1/2 ton gasser that would downshift with accelerator pedal force. Diesel trucks seem the opposite and just want to add more boost (which isn't enough sometimes!)
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post #2 of 2 Old 08-23-2019, 06:38 AM
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Sometimes you have to let off the throttle and then slowly mash it (if that's the proper way to explain) and almost trick the truck into a lower gear for power. My 4r100 doesn't shift differently when tow mode is engaged, just delays overdrive more so sometimes I can let off the gas just a bit on a long hill and roll into it and get the truck into a lower gear for long hills/heavy tows etc.

Something to try. Also try it without tow/haul mode. sometimes I did that with my 6.0l with the 5r100 I was able to keep it in a lower gear longer by playing with the throttle.

after that you'll need a custom tow tune etc.

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