2015 Chevy 2500 (Gas)

[Timcharlie]

Hey guys,
Had an experience recently that I had not encountered before. We own a 2016 Cougar 32FBS and tow her with a 2015 Chevy 2500 (gas). Our last trip took us into the Endless Mountains of PA. Numerous hills along the way and on the way down on those hills, I noticed the RPM's would rev close to 5000. I had the truck in Tow Mode so was this the trucks way of assisting in braking?

Thanks for your responses.

Tim

[Tbos]

My 2014 1500 Silverado will do the same thing. You need to disable the engine braking or shift it into manual and control it that way. It's only happened a couple times but it is unnerving.

[bsmith0404]

That is exactly what it is. The truck is using the engine/transmission to control speed. It sounds bad, but realistically the engine components can handle the stresses. The fuel system isn't really dumping any fuel into the chamber, so the combustion process isn't taking place. Your engine is just pumping air and using the compression process as an engine brake. That is why the computer downshifts and increases RPMs to give more compression strokes.

[KY_wildcat]

To disable engine grade braking hold on the tow mode selector button for 5 seconds. Mine annoys me on minor hills sometimes, but if I am in an extended braking situation I leave it on.

[TAZ23]

That is exactly what it is. The truck is using the engine/transmission to control speed. It sounds bad, but realistically the engine components can handle the stresses. The fuel system isn't really dumping any fuel into the chamber, so the combustion process isn't taking place. Your engine is just pumping air and using the compression process as an engine brake. That is why the computer downshifts and increases RPMs to give more compression strokes.

X2
It's supposed to do that. Your transmission is down shifting to help control speed going down hill. Gas engines on Ford, Chevy, and Ram all do it. I just let it go, It saves on the brakes, and the engine is built to handle the RPM's.

[Timcharlie]

Guys,
Thanks for the responses. I was thinking that was the case but wanted to get other feedback. It can be a little unnerving, but now that I know for sure, it will settle my nerves, as well as my wife's nerves, on our next trip.

Tim

[shov]

As mentioned above, it is the way these engines were designed and perfectly normal operation. Higher engine RPM's under deceleration is completely different than high RPM's under acceleration. Don't be concerned it's your truck and computers way of keeping you safe and those around you.

[CaptnJohn]

The GAS engine is designed that way. It will run high RPM climbing mountains too. It downshifts the transmission to brake and climb. Diesel is a whole different ball game.

[msubobcats]

Also I thank you for the great explanation.

[Turbocohen]

Tim, I am a former dealer tech from long ago and more recently worked for a GM supplier. What you describe is normal tow haul mode operation. If you perform normal routine maintenance there is no need to worry about decel mode engine braking. The ECU is programmed to manage brake input which shifts the trans and fuel off-wide open throttles the engine for additional braking under some cases. Leave it in tow haul mode and notice that the ECU lets you tap/shift the transmission with the brake and throttle pedals. Tap the brakes once and ecu downshifts a gear, tap again, etc. Tap throttle and it up shifts. Hold throttle open while on level or hilly ground and the ecu will hold the low gear. Over time the algorithm learns how you drive and will adapt somewhat.

[jmak]

Much better to have your engine rev up to keep your speed under control than over using your brakes and having your brakes overheat.

[Desert185]

I wish folks in sedans traveling the Sierra knew how to do this by downshifting their autos. I'm tired of following the brake light brigade and smelling hot brakes.

I drove my cousin's Subaru the other day and used the paddle shifters. Hardly touched the brakes.

[busterbrown]

A new pet peeve discovered after several long trips with our trailer over hilly countryside: those drivers who brake incessantly when coming down from an elevation forcing me to change lanes or engage my own brakes. Tow haul mode active on my SUV is sliced bread when navigating the mountains.

[MissJordan]

Sounds normal to me, living in the mountains of western Montana that would drive me nuts, our gasser didn't last long and we went diesel after the first couple trips


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[Desert185]

Turbo power going uphill and exhaust brake going downhill. Nothing like a diesel TV in the mountains.

[Turbocohen]

Agree, but often times after arriving at the destination its nice to have the convenience and cost savings of a gas vehicle. I have both and while pulling the Ram diesel gets it done well but the Suburban HD has the passenger capacity.

http://www.gmfleet.com/chevrolet/suburban-hd-heavy-duty-suv.html

[JRTJH]

Agree, but often times after arriving at the destination its nice to have the convenience and cost savings of a gas vehicle. I have both and while pulling the Ram diesel gets it done well but the Suburban HD has the passenger capacity.

http://www.gmfleet.com/chevrolet/suburban-hd-heavy-duty-suv.html

This quote is from the link you posted. As such, it pretty much eliminates the vehicle as an option for anyone who's a member of the forum....

"Suburban HD is available only to Fleet buyers. The listed features are based on the LS trim level unless otherwise noted."

[Turbocohen]

They offered the 2500 through 2013 then when the model change over occurred there was a delay. The 2018 civilian model is supposed to return about this time next year per my dealer.

[JRTJH]

They offered the 2500 through 2013 then when the model change over occurred there was a delay. The 2018 civilian model is supposed to return about this time next year per my dealer.

Let's hope it's more functional than the one in your link. The max trailer towing capacity listed (in two places on that website) is 3,000 pounds. Yes, there's only three zeros behind that three. You could hardly tow a "good sized pop-up with it....

[Turbocohen]

Yeah I know they say this. Its the "GSA SPEC" they issue because the model is mostly for armored up fitters. Its the same mechanicals as a pre 2015 2500 HD suburban adapted to the new body style. I have towed 11,000 with mine no prob..