SIC_HDPP

So I towed a 29' trailer today with atv's , gear, tools etc. I have noticed a weird issue when in tow/haul mode. When I floor or and let off the gas, the truck will not down shift and will rev and 4,000. I have to dis engage tow/haul mode to it to up shift. This has done it before and after my tune. Is this normal???

blacklion

I had the same issue this past weekend. I was towing a 26ft TT and after I it would drop into 4th when I accelerated on the highway and would not go back into 5th until I disengaged tow mode. My trip to get the trailer I got 18+ mpg, but on the way back with the trailer I dropped to 8 mpg...

mrgooden

I pulled this off another forum so i do not have to type much on the phone.

"Tow haul mode, changes the shift strategy, and raises the line pressure, to reduce the chance of slippage, causing heat build up. It is recomended always when towing or hauling. Unlike the old days, when the tranny's had OD, the old version simply turned off the OD. The new design, doesnt have the OD but another gear, and The tow haul mode switch, will change the perameters of the shift requirements. Holding gears longer, downshifting earlier, not unlocking the converter, on decents, down long hills reducing brake fade."

I don't really tow, but probably prevents downshifts in certain conditions.


Richard

powerboatr

I am not getting your concern
can you re word it or be more detailed


with tow haul its normal to hold gears longer, and not up shift as soon as with tow haul turned off

not sure about your statement of flooring it then letting off, are you flooring it then jumping off the pedal. that will really cause some odd shifting.

towing is not the same as normal. towing by flooring the throttle only wastes fuel and induces unnecessary stresses to the driveline
you should roll into taking off and let it find its "norm" for accelerating
WOT does not equal best performance, holding wot, causes revving through the power band to the flat spot or peak, which usually results in spent fuel for less output of power
best case is to let it shift at max tq, to ensure best performance under load.

SIC_HDPP

I was forced to merge and I need gain speed quickly to keep pace with traffic. When I let off the pedal the rpm's stayed at about 4,000. My concern is why it's not downshifting and I know tow/haul holds gears longer. I was on flat ground and did not press the accelerator for 10 seconds. I will try taping the brakes next time to see if it causes a down shift. Coming from an 05 it would up shift once I got off the pedal.

RES4CUE

That is normal, also it is designed that if you tap the brakes it will downshift for hill control so you don't wear out the brakes.

I use tow/haul during normal driving in the city.

dsg2003mach1

still not getting your post,

is it holding the higher gear and spinning up to 4000rpm so basically its not able to pull because its a gear too high?

or is it downshifting you hit the throttle then when you let off its not upshifting to bring the rpms down?

blacklion

I might be wrong here, but do you mean it would shift into a higher gear instead of down shift?

My concern was when I needed to accelerate it would down shift from 5th to 4th; doing 60-65 on flat ground. Once I get to just under 70 I would attempt to hold that speed. I drove for almost a mile on a flat surface and it would not shift back into 5th. I stayed in 4th doing 4k+ RPM. Disengaging tow mode then reengaging would allow the transmission back into 5th. This happened a few times after the 2 hour drive.

disturbed3003, I'm not trying to jack your thread, just describing my issue to see if it is similar to yours.

SIC_HDPP

[QUOTE="blacklion;3038725"]I might be wrong here, but do you mean it would shift into a higher gear instead of down shift? My concern was when I needed to accelerate it would down shift from 5th to 4th; doing 60-65 on flat ground. Once I get to just under 70 I would attempt to hold that speed. I drove for almost a mile on a flat surface and it would not shift back into 5th. I stayed in 4th doing 4k+ RPM. Disengaging tow mode then reengaging would allow the transmission back into 5th. This happened a few times after the 2 hour drive. disturbed3003, I'm not trying to jack your thread, just describing my issue to see if it is similar to yours.[/QUOTE

I'm having the same issue. It just seems weird that it won't up shift when holding a constant speed on level ground. If I accelerate normally it with shift just fine. It only happens when coming off of WOT In my case.

tcp2

This is a normal behavior of the transmission. The tow/haul mode has a "feature" where it will up shift (6 to 5, 5 to 4, etc) if the truck is accelerating with your foot off the gas pedal. You can force this action quicker if you tap your brakes or hold your brake while the truck is still gaining speed (like rolling downhill with a heavy trailer).

What is happening in your case is you have made the truck accelerate at a relatively fast rate by hitting WOT. As soon as you let off the gas pedal completely, the truck is thinking it is still accelerating without any gas pedal input and will try to use engine braking to keep its speed. If it could up-shift (4-3, 3-2) without over-revving the engine, it would probably try that as well, but at 4000 rpm it can't safely do that, so what it does is hold that gear until you click off tow/haul or gently get back on the gas. If you just put a little bit of pressure on the gas pedal at that point it will shift back down through the gears until it hits normal running speed again. Until it sees the gentle input on the gas pedal, it thinks you are trying to use engine braking to slow down and will hold that gear.