Disappointed in towing performance

[GearHead71]

Quick stats first:

 

Old Tow Vehicle:

2017 Ram 1500 Laramie

Crew Cab

5.7L gas

5'7" bed

3.21 Gears

Max Towing: 8500lbs

Max Payload: 1280lbs

 

New Tow Vehicle:

2020 GMC 2500 SLE

Crew Cab

6.6L Gas

6'9" Bed

3.73 Gears

Max Towing: 14,500lbs

Max Payload: 3200lbs

 

Camper:

26' Jayco Travel Trailer

Roughly 6000lbs

Roughly 600lb tongue weight

 

Quick story:

I bought the camper last year and towed it with the Ram 1500.  The Ram only struggled on steep grades up in the mountains but I decided to upgrade to the GMC 2500 mostly for the drastic increase in payload but also to "future proof" us in case we decide to get a larger camper down the road.

 

The GMC 2500 was a bit disappointing in the mountains.  The road the RAM struggled on the GMC was really hurting on.  At 55mph driving up relatively steep grades the truck was constantly hunting for gears.  Worse than that though, it would get "stuck" in a gear it wouldn't downshift.  At one point, I had it floored at 55mph and it couldn't keep up, it eventually slowed to 45mph and still didn't downshift.  Finally, I put it in "low" and forced it to down shift which it did.  The kind of embarrassing part was my father-in-law was towing a similar size trailer with his 2014 Tundra and my buddy was towing a similar size trailer with his 2019 Ram 1500 and both were following me.  Neither of them struggled as bad up that same incline and could have easily passed me.

 

Do I just need to leave it in "L" and force it to downshift.  I was trying to trust the powertrain engineers and leave it in tow/haul mode thinking the truck would do what it needed to to maintain speed.   It seems like the culprit is the 6 speed transmission.  It's like it needs another gear.  At 55mph climbing hills it's either redlining in 1st gear or only at 3000RPM in 2nd gear with no power.  (I could be mistaken, it might be hunting between 2nd and 3rd, but I think it was between 1st and 2nd).

 

One positive I will say is the truck did AWESOME on downhill grades.  It would downshift right when I wanted to and the engine braking was really impressive.  Barely used the brakes at all.

 

I can give more details if needed, but now I'm worried about getting a larger camper given how much the truck struggled with the relatively light camper we currently have. 

Edited September 1, 2020 by GearHead71

[newdude]

With the 6 speed, the culprit was them switching back to 3.73 gears as they had 4.10 gears 2015-2019.  If GM wants to keep those 3.73s, it NEEDS the 10 speed.  

 

That said, sometimes manual mode does give you more what you want with the 6 speed as you can pick the gear to keep it in the power.   

 

Did you have tow/haul on?  

[GearHead71]

2 minutes ago, newdude said:

With the 6 speed, the culprit was them switching back to 3.73 gears as they had 4.10 gears 2015-2019.  If GM wants to keep those 3.73s, it NEEDS the 10 speed.  

 

That said, sometimes manual mode does give you more what you want with the 6 speed as you can pick the gear to keep it in the power.   

 

Did you have tow/haul on?  

Yeah, I was thinking about looking into regearing it.  It's so new that I wasn't sure if any shops around me would have done one yet though.  Do you know if the front/rear axles are the same as the 2019s?

 

I did have tow/haul mode on.

[Logan Lanfear]

If im not mistaken the Ram that you had came with an 8 speed right? The Hemi for that year also had 395 horsepower. Comparing that to the 2020 GMC 6.6 with only 401 horsepower. The drawback seems to be the 6 speed that your GMC.  I would use manual mode on hills to keep the truck in the power band. Im assuming the truck felt much more planted with the 3/4 ton suspension.  A larger camper could still be very much in your future.  You're just working with a an equally powerful engine with a heavier truck. 

[GearHead71]

39 minutes ago, Logan Lanfear said:

If im not mistaken the Ram that you had came with an 8 speed right? The Hemi for that year also had 395 horsepower. Comparing that to the 2020 GMC 6.6 with only 401 horsepower. The drawback seems to be the 6 speed that your GMC.  I would use manual mode on hills to keep the truck in the power band. Im assuming the truck felt much more planted with the 3/4 ton suspension.  A larger camper could still be very much in your future.  You're just working with a an equally powerful engine with a heavier truck. 

You are correct, the RAM had an 8 speed.  it definitely feels like the 6 speed in the GMC could use at least one more gear.  Trying to maintain 55 mph up a hill you are either screaming in one gear or only at around 3000RPM in the other gear with no power.

 

I will try keeping it in manual mode next time, but I also don't want to just leave it in that lower gear and redline all the way up the incline.  I'm wondering if re-gearing will help.  I'll have to see what that does to each gear range though, it might just move the problem to a different speed or different pair of gears.

[Tomato]

I would also try putting it on cruise control. My Duramax's have always done well at maintaining a tight speed range on steep grades with cruise on (and tow/haul on).

[gSwift]

This is the main reason I went with the diesel, for the 10 speed. If the gasser had at least an 8 speed I might would have considered that more.

[flyingfool]

whats the trans temps durring the tow?  if you get over a certain temp, the tcm defaults into high temp shift tables.. start there before spending big money on gears,  get the tcm tuned..

[GearHead71]

I would also try putting it on cruise control. My Duramax's have always done well at maintaining a tight speed range on steep grades with cruise on (and tow/haul on).

I will try that, thanks.

This is the main reason I went with the diesel, for the 10 speed. If the gasser had at least an 8 speed I might would have considered that more.

Yeah, I'm wishing the gasset had at least an 8 speed too.

whats the trans temps durring the tow?  if you get over a certain temp, the tcm defaults into high temp shift tables.. start there before spending big money on gears,  get the tcm tuned..

The transmission temp was steady during the entire 4-hour trip. I was actually really impressed that it never crept up.

 

I haven't heard about tuning the TCM. I will look into that, thanks!

 

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[Londart2020]

2 hours ago, Logan Lanfear said:

If im not mistaken the Ram that you had came with an 8 speed right? The Hemi for that year also had 395 horsepower. Comparing that to the 2020 GMC 6.6 with only 401 horsepower. The drawback seems to be the 6 speed that your GMC.  I would use manual mode on hills to keep the truck in the power band. Im assuming the truck felt much more planted with the 3/4 ton suspension.  A larger camper could still be very much in your future.  You're just working with a an equally powerful engine with a heavier truck. 

And probably only weighed 4500 lbs, and the new truck is more than likely 7500+

[Colossus]

I'd give it a year or so and you'll then see some performance tuners come out which will help with your situation and which will also allow you to re-calibrate the onboard computer(s) to take advantage of re-gearing it... or maybe you don't have to do it if you re-gear the diff, only the tire size.. I may be confused.  You were doing the right thing though by upgrading to a 3/4 ton to safely tow! 

[ShotgunZ71]

I've not had any situations where the truck struggles. Most of my trips have been in relatively flatlands or rolling hills. On a trip home in the rolling hills, I put the transmission in M4 and it performed well at interstate speeds. I have found that keeping the RPM in the 2500-4200 range makes it happy. What I always remember is that in these new gassers, 70 mph is 3000 RPM in 4th gear and 4000 RPM in 3rd gear. Kind of gives you an idea of where you need to be for moderate to steep inclines (and descents). The torque curve on these engines is pretty flat, so you don't necessarily have to keep it at 4000, just keep it above 3000 and you should notice a difference.

[Hagar68]

Another viewpoint:

8k lb travel trailer. 

=original TV was '13 tundra, 5.7, tow pkg, 4.3 gears

=Bought '19 chevy 2500 duramax

,=15 months later, traded for 20 gmc 2500 gasser

 

Gasser is 2000 lbs heavier than tundra empty, and on a camping trip the truck  weighs 9700 lbs including 1000 lb tongue wt plus remaining 7k lb trailer wt.

 

 i'm very pleased so far with towing.  haved pulled up a couple of 7% grades 2-3 miles long and was able to pass some but not all traffic, nothing like the diesel but completely respectible.

 

First time i pulled it had some downshift burps but has done fine since then.  its a little noisier than tundra but to be expected with weight and

gear difference.

 

Tow/haul, chevron 89 octane, 10% ethanol

You might have the dealer see if any codes stored in engine or trx.

 

I think i read gm completely redesigned the axles for strength, so might be hard to do gear swap

 

I have banks idash left over from the diesel and banks said they would eventually tune this engine.

 

I really wonder if you have a trx programming problem.

 

[GearHead71]

1 hour ago, Hagar68 said:

Another viewpoint:

8k lb travel trailer. 

=original TV was '13 tundra, 5.7, tow pkg, 4.3 gears

=Bought '19 chevy 2500 duramax

,=15 months later, traded for 20 gmc 2500 gasser

 

Gasser is 2000 lbs heavier than tundra empty, and on a camping trip the truck  weighs 9700 lbs including 1000 lb tongue wt plus remaining 7k lb trailer wt.

 

 i'm very pleased so far with towing.  haved pulled up a couple of 7% grades 2-3 miles long and was able to pass some but not all traffic, nothing like the diesel but completely respectible.

 

 

First time i pulled it had some downshift burps but has done fine since then.  its a little noisier than tundra but to be expected with weight and

gear difference.

 

Tow/haul, chevron 89 octane, 10% ethanol

You might have the dealer see if any codes stored in engine or trx.

 

I think i read gm completely redesigned the axles for strength, so might be hard to do gear swap

 

I have banks idash left over from the diesel and banks said they would eventually tune this engine.

 

I really wonder if you have a trx programming problem.

 

What is trx programming? I'll ask the dealer and see if they can look at it. 

 

We are camping again this weekend (in Breckenridge). I'm curious to see how it does. 

[Hagar68]

Transmission is controlled by a computer.  I just 

Wondered if there were some error messages or codes set that would lead the dealer to a problem that is preventing the downshifts and hurting drivability.

 

I haven't been up a hill yet where I could not maintain the speed limit, AND while staying under 4500 rpm.  I do not normally use cruise in the mountains as it seems to keep rpms too high.