Driving in M5 all the time

bowtiemark · July 4, 2019

29 minutes ago, MikeNH said:

Driving in M5 will not hurt anything other than a loss of fuel economy at higher speeds. In town in every automatic I've ever owned I've locked out overdrive when possible. Driving in M4 or M5 on these trucks is how to do that.

M6 is essentially the same as D, AFM will will activate and make that awful noise. I also feel like it causes hesitation.

You need to check the oil level on your dipstick periodically and look for the level dropping.

I drive in M4/M5 and switch to M6 on the highway generally. On long trips I just use D but there generally is no real difference other than I think grade braking is disabled in "M" mode.

thanks man! you made it real clear! plan on sticking with m5 from now on, truck feels better when in that gear..

Cowpie · July 5, 2019

As a side note, even with my 2500 with 4.10 diffs an no AFM, I generally dive around in M5 most of the time unless I will be going 65 mph or greater. I live rural, and on the rolling hills in my area, being in top gear even with the 4,10 causes a lot of shifting on every little mole hill If I keep RPM's at 2100 or more (that is the point where the L96 6.0 in my 2500 hits 90% torque), it stops a lot of the shifting on many hills in my area. And allowing the trans to go into top gear and shifting all the time on every hill puts more strain on trans and fluid, and also negatively affects fuel economy. Even more so than leaving the trans in M5 and keeping the RPM's a little higher. Fuel use is a function of how much power is needing to be applied. Keeping the RPM's at a point where rotational inertia of the motor is less of an issue and keeping shifting to a minimum actually takes less power and fuel than running RPM's much lower and having to feed fuel to an engine that is below its optimum RPM band where it takes more fuel to overcome rotational inertia and move the vehicle.

Just something else to consider along with the AFM argument. AFM is not the only reason to consider running in M5. I followed this same procedure when I had a 2013 1500 5.3 for a while. That pickup was a poor choice for various reasons so I traded it for a 2500.

Edited July 5, 2019 by Cowpie

Donstar · July 5, 2019

I agree with using m4 or m5 when you want to keep your truck out of the higher gears. These times for me are usually when I use tow/haul mode. For everyday driving I simply use D. My truck automatically finds a way to keep me moving forward smoothly and comfortably. I would far, far prefer a 4, 5 or 6 spd. truck duty manual for total control but this isn't a choice.