Disappointed in towing performance

Ray Pickle · October 13, 2020

I can only guess there is a powertrain issue in your truck. This truck would benefit from a deeper axle ratio, but in my personal experience I have not had ANY problems maintaining 55 up any pass I have been on. That includes numerous passes through the continental divide. I will admit that I will typically pull a grade like the Eisenhower tunnel pass at 40 to 45 mph just because it is easier on the truck and therefore my wallet. That being said those grades are the rare exception both in grade and elevation.

GearHead71 · October 13, 2020

4 minutes ago, Ray Pickle said:

I can only guess there is a powertrain issue in your truck. This truck would benefit from a deeper axle ratio, but in my personal experience I have not had ANY problems maintaining 55 up any pass I have been on. That includes numerous passes through the continental divide. I will admit that I will typically pull a grade like the Eisenhower tunnel pass at 40 to 45 mph just because it is easier on the truck and therefore my wallet. That being said those grades are the rare exception both in grade and elevation.

Heading eastbound up to Eisenhower is definitely one spot I can't maintain 55mph. Maybe I just need to learn patience and take it at 45. Haha.

But that was the spot where it was embarrassing. My father in law passed me in his 2014 Tundra and my buddy passed me in his 2019 Ram 1500 (we all have similar weight trailers). I was the only one that couldn't maintain the speed limit in my brand new "big" truck.

Ray Pickle · October 13, 2020

As someone has already mentioned , big boy truck weighs 7k empty. There is more to competent towing than how fast you can pull a 7% grade at 11k ft. I guarantee you my gasser will pull my 5th wheel up the "ike" faster than astock Tundra or 1500 5.7! Clearly neither of those vehicles should even attempt but?

GearHead71 · October 13, 2020

So just to have some hard numbers to look at I looked up the gearing for the 6 Speed:

Gear	Gear Ratio
1st	4.03
2nd	2.36
3rd	1.53
4th	1.15
5th	8.5
6th	0.67

Other stats:

Front and Rear Gear Ratio: 3.73:1

Engine Redline: 5600RPM

Max Torque: 464 @ 4000RPM

Max HP: 401 @ 5200PRM

Tire Size: 265/70R17 (without actually measuring my tires, that's about a 99.3 inch circumference)

Given this, here are the engine RPMs at 3 different MPH (RPMs in bold are above redline):

55MPH:

Gear	Engine RPM
1st	8794.345637
2nd	5150.038636
3rd	3338.796234
4th	2509.552725
5th	1854.886797
6th	1462.08724

60MPH:

Gear	Engine RPM
1st	9593.831604
2nd	5618.223966
3rd	3642.323165
4th	2737.693882
5th	2023.512869
6th	1595.004262

65MPH:

Gear	Engine RPM
1st	10393.31757
2nd	6086.409297
3rd	3945.850095
4th	2965.835039
5th	2192.138942
6th	1727.921283

As you can see (take the trailer out of the equation), at 60MPH the LOWEST gear I can use is 3rd and the RPMs are only at 3642. That's a little below where the max torque is, and well below max hp. I'm going to play around with what re-gearing will look like (either 4.10 or 4.56).

Take even 55MPH. Your options are either almost 5200 RPM (screaming) or 3340 (no power). This is exactly what I've been experiencing.

To me, it still seems like it's missing a gear between 2nd and 3rd. Either that, or maybe they should have "shortened" the gap between 2nd and 3rd. At 60 MPH it's a 2,000 RPM jump between 2nd and 3rd (even though you can't use 2nd gear) but only a 900 RPM jump between 3rd and 4th; 715RPM between 4th and 5th. I know those shouldn't be linear, but still seems like a big gap.

Edited October 13, 2020 by GearHead71

GearHead71 · October 13, 2020

1 hour ago, Ray Pickle said:

As someone has already mentioned , big boy truck weighs 7k empty. There is more to competent towing than how fast you can pull a 7% grade at 11k ft. I guarantee you my gasser will pull my 5th wheel up the "ike" faster than astock Tundra or 1500 5.7! Clearly neither of those vehicles should even attempt but?

I'm with you! And I LOVE the truck and the towing other than this one issue. Unfortunately for me, the times it struggles and can't maintain the speed limit kill the rest of the experience. Maybe a re-gear will help me, or maybe I just need to get over this one instance of under-performance (that would be cheaper haha)

Edited October 13, 2020 by GearHead71

Ray Pickle · October 13, 2020

If your truck is 2wd rear gearing is reasonable. I would put 4:10 in mine if it was 2wd. Not going to invest in 2 gearsets for the improvement in the occasional steep mountain towing I do. Probably worth it if you live in that area and tow heavy often through that terrain.

GearHead71 · October 13, 2020

10 minutes ago, Ray Pickle said:

If your truck is 2wd rear gearing is reasonable. I would put 4:10 in mine if it was 2wd. Not going to invest in 2 gearsets for the improvement in the occasional steep mountain towing I do. Probably worth it if you live in that area and tow heavy often through that terrain.

Mine is 4WD. We tow in the mountains about 6 times a year. The only thing that makes me nervous is I'm only towing 5500lbs. I bought this truck so we could get a bigger camper (around 9500lbs). Given how it struggles now in the mountains, I'm not sure how much worse it will do with the larger camper.

I'm going to call around and see how much a re-gear is. Also, not sure the jump to 4.10 would be enough of a difference. Might need to go up to 4.56 and at that point you need a new carrier as well...

kenny_r · October 13, 2020

I have a 2017 6.0 and to me it seems like it will pull all day long at 3500rpm. I’m usually loaded around 8k traveling up to 7k ft elevation. I wanna say I’m locked into 4th.[emoji848]

ShotgunZ71 · October 13, 2020

Most of the time, if I'm in rolling hills or mountainous area, I'll lock out 5th and 6th on the interstate to keep the RPM above 3000. If the highway speed is slow enough, I'll lock out 4th as well. I just like to stay in the 3-4k range when going up and down inclines, so the speed doesn't vary so much and also so that you have a bit better engine braking. I've not had any issue with my truck and camper getting up to speed on any grade yet. That's pulling a 42', 14.5k lb 5th wheel, also.

However, I will say that if I encounter a normal driving situation (grade or otherwise)where the truck will not maintain speed or even attempt to maintain or gain speed, I will absolutely look at other options. Those will likely be a Ford with the 7.3 gas engine or a diesel, be it Duramax or Powerstroke.

I feel that there is something amiss with the OP's truck or programming, etc. The truck should in no way struggle up that grade with that light of a load. Something doesn't make sense, especially since the truck has performed that poorly multiple times for him.

Colossus · October 14, 2020

So is the performance the same with what the OP encountered as well as with what that truck video group that tests the trucks? 6.6 just sucks in the mountains?

KARNUT · October 14, 2020

When I was pulling back in the day up to the late 90s, some in the early 2000s. The HP and TQ was around 165-200 and low 400 in diesel. You had one transmission gear choice after 45 mph shift to one to one or 4th gear or drive in auto. Usually 410 gear. Gas engines depending on gearing, I ran 410. I could downshift even at 60. Gas engines could be had with 300HP around 400 TQ. I used 3/4 ton at that time Ram V-10. My trailer along was 7500 lbs.
Maintaining HWY speed in drive or 4TH with a stick wasn’t a problem at 3K RPMs. I was left with one gear to down shift when needing. As soon as I lost speed on a hill I did that and maintained speed. Seems there’s either a know how problem or a gearing problem. I would want 3K at 60 in a drive gear not over drive. With the gear spacing you should be able to have over drive empty driving. And two gears for hill pulling and maintaining speed. Remember my trailer was 7500lbs. My tractor was 14K more and had a cab. I can’t believe GM would miss the boat that bad. Something’s amiss.

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GearHead71 · October 14, 2020

17 minutes ago, KARNUT said:

When I was pulling back in the day up to the late 90s, some in the early 2000s. The HP and TQ was around 165-200 and low 400 in diesel. You had one transmission gear choice after 45 mph shift to one to one or 4th gear or drive in auto. Usually 410 gear. Gas engines depending on gearing, I ran 410. I could downshift even at 60. Gas engines could be had with 300HP around 400 TQ. I used 3/4 ton at that time Ram V-10. My trailer along was 7500 lbs.
Maintaining HWY speed in drive or 4TH with a stick wasn’t a problem at 3K RPMs. I was left with one gear to down shift when needing. As soon as I lost speed on a hill I did that and maintained speed. Seems there’s either a know how problem or a gearing problem. I would want 3K at 60 in a drive gear not over drive. With the gear spacing you should be able to have over drive empty driving. And two gears for hill pulling and maintaining speed. Remember my trailer was 7500lbs. My tractor was 14K more and had a cab. I can’t believe GM would miss the boat that bad. Something’s amiss.

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I really hope something is amiss. I love this truck otherwise but this is really making me regret my decision. I'm not a Ford guy but looking at the 7.3 gas with the 10 speed is making me wonder.

I really think if my truck had the 10 speed I wouldn't be having this problem. It just needs a gear between second and third to bring the engine RPMs back near the power band at 60 miles an hour

KARNUT · October 14, 2020

I really hope something is amiss. I love this truck otherwise but this is really making me regret my decision. I'm not a Ford guy but looking at the 7.3 gas with the 10 speed is making me wonder.

I really think if my truck had the 10 speed I wouldn't be having this problem. It just needs a gear between second and third to bring the engine RPMs back near the power band at 60 miles an hour

I hear you. I definitely wasn’t a Ram guy when I had my V-10. Diesels at the time didn’t have enough gear spacing for downshifting on hills. You had to be at 45 mph before going down to 3rd gear. The gas could go at 60. I was pulling pretty heavy. My V-10 had no problem pulling my empty 7500lb trailer in 5th overdrive. It was 300hp 400 ft lbs of TQ. It had a 355 gear. Our auto V-10 had 410. My Cummings diesels had 355. My gear spacing on the diesel was 45 in third 60 in fourth 92 in over drive. Maintaining speed in the diesel was harder than the V-10. Different game now.

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Ray Pickle · October 14, 2020

Again TFL tests require they do no manual shifting for the sake of uniformity. I would make a significant bet the g.m. and Ford would be within 30 sec. Going up the Ike if both where maually shifted to their best advantage. If the Ford was equipped with standard 3.55 I believe it would be behind. What their test does prove is that Ford has been less conservative in their tuning choices relating to shift strategies. The 2 engines are nearly identical in torque from 2800 rpm up to over 4500 rpm. In spite of the significant displacement differences. The G.M. gets better mileage and the Ford with optional 7.3 and optional 4.30 pulls a little better. The 10 speed transmission is an advantage, but on a gasser with a 1k to 6k operating range, not as significant as for a diesel .

GearHead71 · October 14, 2020

I did the same exercise for the Ford 7.3 (w/ 3.55 and 4.30) as well as the RAM with the 6.4 (3.73 and 4.10). I know I'm only looking at one specific speed range (55-65MPH) but that's where mine is struggling. What you can see from the data below is at 60MPH both the RAM and Ford (in BOTH axle gear options) have a gear (or TWO) in the 4000-5000 RPM range whereas the GMC does not. (I had a hard time finding redline for the RAM 6.4L hemi with the 8HP75 trans as well as the for Ford 7.3 with the 10R140, but this will get us close enough).

RAM 2500 6.4L Hemi (redline: 5800 RPM)
Diff Gears	3.73
			55 MPH	60 MPH	65 MPH
Gear	Gear Ratio	Final Drive	Engine RPM	Engine RPM	Engine RPM
1st	4.71	17.5683	9782.917	10672.27	11561.63
2nd	3.14	11.7122	6521.945	7114.849	7707.753
3rd	2.1	7.833	4361.81	4758.339	5154.867
4th	1.66	6.1918	3447.907	3761.353	4074.799
5th	1.28	4.7744	2658.627	2900.321	3142.014
6th	1	3.73	2077.053	2265.876	2454.698
7th	0.83	3.0959	1723.954	1880.677	2037.4
8th	0.66	2.4618	1370.855	1495.478	1620.101

RAM 2500 6.4L Hemi (redline: 5800 RPM)
Diff Gears	4.1
			55 MPH	60 MPH	65 MPH
Gear	Gear Ratio	Final Drive	Engine RPM	Engine RPM	Engine RPM
1st	4.71	19.311	10753.34	11730.92	12708.49
2nd	3.14	12.874	7168.894	7820.612	8472.329
3rd	2.1	8.61	4794.483	5230.345	5666.207
4th	1.66	6.806	3789.925	4134.463	4479.002
5th	1.28	5.248	2922.352	3188.02	3453.688
6th	1	4.1	2283.087	2490.641	2698.194
7th	0.83	3.403	1894.962	2067.232	2239.501
8th	0.66	2.706	1506.838	1643.823	1780.808

Ford F250 7.3L Gas (redline: 5500 RPM)
Diff Gears	3.55
			55 MPH	60 MPH	65 MPH
Gear	Gear Ratio	Final Drive	Engine RPM	Engine RPM	Engine RPM
1st	4.615	16.38325	9123.022	9952.387	10781.75
2nd	2.929	10.39795	5790.104	6316.477	6842.85
3rd	2.132	7.5686	4214.579	4597.723	4980.866
4th	1.773	6.29415	3504.901	3823.528	4142.156
5th	1.519	5.39245	3002.789	3275.77	3548.75
6th	1.277	4.53335	2524.398	2753.889	2983.38
7th	1	3.55	1976.819	2156.53	2336.241
8th	0.85	3.0175	1680.297	1833.051	1985.805
9th	0.687	2.43885	1358.075	1481.536	1604.998
10th	0.632	2.2436	1249.35	1362.927	1476.504

Ford F250 7.3L Gas (redline: 5500 RPM)
Diff Gears	4.3
			55 MPH	60 MPH	65 MPH
Gear	Gear Ratio	Final Drive	Engine RPM	Engine RPM	Engine RPM
1st	4.615	19.8445	11050.42	12055	13059.59
2nd	2.929	12.5947	7013.366	7650.944	8288.523
3rd	2.132	9.1676	5104.983	5569.072	6033.162
4th	1.773	7.6239	4245.373	4631.316	5017.259
5th	1.519	6.5317	3637.181	3967.834	4298.486
6th	1.277	5.4911	3057.722	3335.697	3613.672
7th	1	4.3	2394.457	2612.135	2829.813
8th	0.85	3.655	2035.289	2220.315	2405.341
9th	0.687	2.9541	1644.992	1794.537	1944.082
10th	0.632	2.7176	1513.297	1650.87	1788.442

GMC 2500 6.6L Gas (redline: 5600 RPM)
Diff Gears	3.73
			55 MPH	60 MPH	65 MPH
Gear	Gear Ratio	Final Drive	Engine RPM	Engine RPM	Engine RPM
1st	4.03	15.0319	8794.729042	9594.25	10393.77
2nd	2.36	8.8028	5150.263161	5618.469	6086.675
3rd	1.53	5.7069	3338.941795	3642.482	3946.022
4th	1.15	4.2895	2509.662134	2737.813	2965.964
5th	0.85	3.1705	1854.967664	2023.601	2192.235
6th	0.67	2.4991	1462.150982	1595.074	1727.997

I did look at what would happen if I re-geared to 4.56 (4.10 wouldn't be a big enough change) and that would get me from being stuck at 3600 RPM at 60 MPH with no power to 4450 RPM which is closer to the max torque. I feel like that would solve my problem but my gas mileage would take a hit (this is also my daily driver) and I need to look and make sure I'm not just moving this problem to a different gear/speed range.

GMC 2500 6.6L Gas (redline: 5600 RPM)
Diff Gears	4.56
			55 MPH	60 MPH	65 MPH
Gear	Gear Ratio	Final Drive	Engine RPM	Engine RPM	Engine RPM
1st	4.03	18.3768	10751.73309	11729.16	12706.59
2nd	2.36	10.7616	6296.300272	6868.691	7441.082
3rd	1.53	6.9768	4081.923481	4453.007	4824.091
4th	1.15	5.244	3068.112421	3347.032	3625.951
5th	0.85	3.876	2267.735267	2473.893	2680.051
6th	0.67	3.0552	1787.508976	1950.01	2112.511