6 speed transmission questions.

Are you in charge now? You finally posted some factual information, not "I am going by memory". Maybe we better quit while we are ahead.

This thread has been long on facts, and short on comprehension.
And consistent with who posts what.
Add something or move on please.

Nice to see some facts quoted.

That's when using cruise control, grade braking is when using the brakes. De-activate cruise and the vehicle momentarily upshifts and freewheels, until it figures out that you need engine braking. That's not unique to GM, they all screw up the transition I believe the functionality is similar to the 2013's, mine was a 2011 and acted much the same. Except the hill start feature....

GM -
"Tow/Haul mode, activated by a button on the shift lever, modifies the standard six-speed transmission’s shift mapping to take full advantage of the Sierra’s powerful new EcoTec3 engines. Under acceleration, shift points are higher for more power, while downshifts are initiated earlier to promote engine braking, reducing wear on the Sierra’s disc brakes.

With Tow/Haul mode engaged, Sierra’s Trailer Grade Braking is activated when the driver lightly applies the brakes. This feature initiates downshifts to assist with braking on long downgrades. In addition to slowing the vehicle more efficiently, Auto Grade Braking can reduce brake rotor temperatures by 100 degrees Celsius during a braking event.

For drivers who prefer full control over their truck’s shifting, improved TapShift controls on the shift lever are backed by a patent-pending shift algorithm that improves shift response time by up to 60 percent compared to previous systems. When the TapShift controls are in use, Sierra’s Trailer Grade Braking is deactivated because the driver is manually controlling gearshifts."

http://www.gm.com/article.content_pages_news_us_en_2013_may_0531-gmc-sierra-trailering.html

According to my GM owner's manual:

"Vehicles with a six speed
automatic transmission and a
gasoline engine have Cruise
Grade Braking to help maintain
driver selected speed.
Cruise Grade Braking is enabled
when the vehicle is started and
Cruise Control is active."

Bank of Dad wrote:
What is the trailer braking feature? I did notice as I went downhill(not in tow haul) it did seem to drop down a gear on its own. I felt it downshift. What happens in t/h mode?

When going down a grade of any sort, the transmission will downshift to use the engine as a brake to slow the vehicle down. I'm going by memory here, but I believe on the GM's, tapping the brake once will initiate a drop of 1 gear, a second tap 2, and so forth. Or just hit the brakes sufficiently to control your speed, and it will drop gears appropriately.
Or use the "manual" shift control feature to manually drop to whatever gear lets you use the brake pedal only to adjust your descent speed and not control it.

TomG2 wrote:
It's called hijacking a thread. You wanted to talk about how great your Ford is, the OP asked about a Suburban.

Not really, to many people the Ford manual control is useless, and the GM manual function is mis-understood. ;-)
Anything more to add Tom?

What is the trailer braking feature? I did notice as I went downhill(not in tow haul) it did seem to drop down a gear on its own. I felt it downshift. What happens in t/h mode?

It's called hijacking a thread. You wanted to talk about how great your Ford is, the OP asked about a Suburban.

Bank of Dad wrote:
Gheeese. All I wanted to know was how to use the 6 speed.

Having put 120 000miles on my 2 different GM 1 tons, I would just put it in tow haul, and leave it. It will shuffle a bit, but the computer eventually "locks out" gears progressively as it finds the truck unable to pull them. That way you keep your trailer braking feature. That was my experience that got ME the best results. Sorry for getting off topic.

Saying the same thing five times does not make it true. For me to respond five times makes me the fool.