Hill decent assist

beetle · May 7, 2014

I think what you are noticing is something these trucks do. Basically when coasting down a hill, then fuel supply will be shut off while coasting. So the speed of the wheels are driving the motor. This might feel like its "grade braking" but its not, its a fuel saving feature and has been discussed in another thread. If you shifted into neutral, you would find that the truck freely coasts down the hill. But while in drive, it uses the wheel speed to control the coasting of the vehicle and keep the engine driving so that when you do reengaged the gas, it doesn't have to rev up.

Make sense?

This can be tuned out with a custom tune. As simple as turning on/off a value in the PCM/TCM

*EDIT*

Found it:

from this thread: http://www.gm-trucks.com/forums/topic/160536-question-regarding-transmission-behavior/

I know about the fuel shut off but my tranny will downshift to hold the speed back, sometimes the tach will read as high as 4000 rpm. I'd rather wear out my brakes than scatter the engine, sustained high rpm's without any load is a big no-no.

Silverado-Hareek · May 7, 2014

I know about the fuel shut off but my tranny will downshift to hold the speed back, sometimes the tach will read as high as 4000 rpm. I'd rather wear out my brakes than scatter the engine, sustained high rpm's without any load is a big no-no.

Yeah I hate the way this system feels. My brakes on my 2007 Silverado lasted 95,000 miles before they needed changing so I'm not sure why they felt like a longer life was needed on these new trucks. I'd prefer the truck to coast rather than downshift and pull back using the engine.

fondupot · May 7, 2014

I know about the fuel shut off but my tranny will downshift to hold the speed back, sometimes the tach will read as high as 4000 rpm. I'd rather wear out my brakes than scatter the engine, sustained high rpm's without any load is a big no-no.

I honestly haven't done any mountainous driving where this would come into play. But I'd rather have the engine reving up instead of riding the brakes. Lots of vehicles have this built in now to control downhill descents. If its only for a short period of time, i think it will be ok.

But like I said, if you dont like it you can get it tuned out with a custom transmission tune. One other member says it's as easy as flipping a switch.

beetle · May 7, 2014

I honestly haven't done any mountainous driving where this would come into play. But I'd rather have the engine reving up instead of riding the brakes. Lots of vehicles have this built in now to control downhill descents. If its only for a short period of time, i think it will be ok.

But like I said, if you dont like it you can get it tuned out with a custom transmission tune. One other member says it's as easy as flipping a switch.

Getting that feature tuned out will be a priority, need to do some research on how.....thanks all.

TJay74 · May 7, 2014

I am pretty sure there is no way to tune out the hill descent feature. It is controlled via the BCM which no tuners have access to other than maybe Chris White.