Towing up grades with "M" and 1 gears

APT wrote:
M mode for GM is not quite manual. It is more like range limit for the top gears. The number displayed is the highest gear the transmission will automatically shift into.

I tow in M4 or M5 with Tow/Haul enabled depending on the situation. Same engine/transmission as your van. I tow around 70mph and have had the trans shift into 6th gear. There is not enough torque at 2000rpm to push through the air. So, speed drops, then double downshift to get back to target speed. I lose the grade braking feature in M mode, but I can do that myself by hitting '-'. That engine/trans can sing at 3000rpm for 300k miles.

The correct term would be "semi automatic" for "M", sort of like the olden days where you could by a vehicle that had a transmission that did not have a clutch nor had the automatic valve body. On those you had to manually move and select each gear one at a time but it did it without any clutch pedal..

As always, READ THE MANUALS.

I am sure Ford and GM vary a lot but once again, there should be zero reason to baby sit things..

Some folks seem to get scared that they are harming the engine (lugging or running too high of RPM).. The reality is, now days the power train controls are setup to PREVENT DAMAGE FROM OCCURRING.

If the power train control determines your engine as you are going up a hill is on the verge of "lugging" it WILL downshift to the next lower gear provided the RPM will not exceed redline.

Same happens when descending a hill, the power train control will only downshift to the next lower gear as long as that selection will not exceed redline.

The "M" mode is put there more to satisfy (appease) the folks that got upset when manufacturers dropped all manual stick shift transmissions offerings..

The advances made in automatic transmissions over the last 10+yrs has been amazing but I get it, folks ARE distrusting of advanced features like TOW/HAUL..

In older vehicles that offered 3 and 4 speed automatics it was typically recommended in the manuals to drop a gear if transmission was hunting gears or lock out overdrive when towing.. Those recommendations are no longer in the manuals.. And with older vehicles, a downshift at the wrong RPM could be catastrophic to the engine and transmission.

Here is some of the information in Fords manuals concerning TOW/HAUL, M mode.

Fords 2020 F250 manual..

HERE


"Page 206

Manual (M)
With the gearshift lever in manual (M), the
driver can change gears up or down as
desired. By moving the gearshift lever from
drive position drive (D) to manual (M) you
now have control of selecting the gear you
desire using buttons on the shift lever. See
Understanding your SelectShift
Automatic transmission later on in this
section.

Page 207

Your vehicle has a SelectShift Automatic
transmission gearshift lever. The
SelectShift Automatic transmission gives
you the ability to change gears up or down
without a clutch

To return to normal drive (D) position,
move the shift lever back from manual (M)
to drive (D).
The transmission operates through the full
range of gears.

Forced downshifts

Allowed in drive (D) with the tow/haul
feature on or off.

Press the accelerator to the floor.

Allows transmission to select an
appropriate gear.
Understanding Your SelectShift
Automatic

Transmission
E249567
Note:
When pressing the button on the
gearshift lever, you can cycle through the
available drive modes.
See
Drive Control
(page
267
).
Your vehicle has a SelectShift Automatic

transmission gearshift lever. The
SelectShift Automatic transmission gives
you the ability to change gears up or down
without a clutch.
In order to prevent the engine from running
at too low an RPM, which may cause it to
stall, SelectShift still automatically make
some downshifts if it has determined that
you have not downshifted in time.
Although SelectShift makes some
downshifts for you, it still allows you to
downshift at any time as long as the
SelectShift determines that damage to
the engine does not occur from
over-revving.
SelectShift does not upshift, even if the
engine is approaching the RPM limit. It
must be shifted manually by pressing the
+ button.
Note:
Engine damage may occur if you
maintain excessive engine revving without
shifting.

Page 208

Manual (M)
Moving the gearshift lever to the manual
(M) position allows you to manually select
the gear you desire. Only the current gear
displays. Use the buttons on the gearshift
lever to manually select gears. Press the
+ button to upshift or the
–
button to
downshift. Return the transmission to a
different gearshift position to deactivate
manual control.

Page 268

Tow/Haul
–
For improved
transmission operation when
towing a trailer or a heavy load.
This mode moves upshifts to higher engine
speeds to reduce the frequency of
transmission shifting. This mode also
provides engine braking in all forward
gears, which slows your vehicle and assists
you in controlling your vehicle when
descending a grade. The amount of
downshift braking provided varies based
on the amount you press the brake pedal."

As always folks READ THE MANUALS, MANY of the old recommended procedures of the days gone by have been changed or removed and no longer apply to newer power train systems.