2020 Freightliner vs 3500 GMC Dually at the Ike

Measuring the time required to tow a trailer up a hill is an accurate method of measuring rear wheel hp. It surprises me that the GM didnt smoke the Freightliner.

What percentage of each vehicles towing capacity is the trailer at that weight?

bguy wrote:
What percentage of each vehicles towing capacity is the trailer at that weight?

And how close is each to the rear axle weight rating ? This is a perfect example that "payload" is primarily a registration class derived number. This Freightliner is likely capable of being registered up to class six.

They praise the performance of the engine brake on the Freightliner over the performance of the exhaust brake on the GMC, however, if more weight had been loaded into the trailer the Duramax would have held 50 mph yet the Freightliner would have required additional brake applications. Comparing two trucks on one hill with only one weight in tow doesn't really offer an honest comparison. I'm having trouble understanding why the GM slowed down as much as it did going up the hill ..... something doesn't add up. Even back in 2015 (with 396 HP and 765 lb ft) the Duramax towed 19000 lbs up the Ike in just under 10 minutes. link

Duramax FTW!!!

Anyone know what the gross weight of each combination was?

Also when the pickup goes into downshift run to the governor upshift nope can’t pull it downshift try again upshift nope can’t pull it mode why not select the lower gear and let it pull near its max power rating, like a truck driver does it?

4x4ord wrote:
They praise the performance of the engine brake on the Freightliner over the performance of the exhaust brake on the GMC, however, if more weight had been loaded into the trailer the Duramax would have held 50 mph yet the Freightliner would have required additional brake applications. Comparing two trucks on one hill with only one weight in tow doesn't really offer an honest comparison. I'm having trouble understanding why the GM slowed down as much as it did going up the hill ..... something doesn't add up. Even back in 2015 (with 396 HP) the Duramax towed 19000 lbs up the Ike in just under 10 minutes. link

**** man....that new Dirtymax driver is a sand baggin bisnatch then! He must have stock in Freightliner!

Looks to me that the GM de-fueled and/or ****** timing (cutting power) because EGT's were probably getting too hot. Big difference between initial power and sustained power.

The GM's 445 horsepower is barely sustainable towing that heavy of a load with a stock turbo in a deleted truck without getting the EGT's too high so I doubt an emissions intact truck can sustain that. It would have to de-fuel/****** timing to keep the EGT's in check.

ShinerBock wrote:
Looks to me that the GM de-fueled (cutting power) because EGT's were probably getting too hot. Big difference between initial power and sustained power.

The GM's 445 horsepower is barely sustainable towing that heavy of a load with a stock turbo in a deleted truck without getting the EGT's too high so I doubt an emissions intact truck can sustain that. It would have to de-fuel to keep the EGT's in check.

You may be right but isn't it surprising that the 2015 Duramax out performs the 2017? I would have thought the turbo on the 2017 would pump more air and be capable of higher power with lower EGTs.

4x4ord wrote:

You may be right but isn't it surprising that the 2015 Duramax out performs the 2017? I would have thought the turbo on the 2017 would pump more air and be capable of higher power with lower EGTs.

Not really, the 2015 may have had a more conservative tune that did not need to defuel/cut timing to keep EGT's in check. While a larger turbo can help reduce EGT's, there is still the DPF and SCR trapping heat and restricting flow. Outside temps also play a big role in EGT's and sustainable power as well. If the outside temps were a lot cooler with the 2015(which it looks like it was from the snow in the background) than they were in this test with the 2017, then the 2015 could sustain higher power levels without having to de-fuel/pull timing. If you really want to be surprised, the 385 hp 2014 Ram 3500 towed that same trailer that 2015 GM in the link you posted even quicker in 9:38( LINK ).


What a lot of people don't know is that just like a gas engine will pull timing and reduce power if knock is detected, so will a diesel if EGT's or other temps get too high.