The Inevitable Comparison: GM 6.6 vs. Ford 7.3

ShotgunZ71 · February 3, 2020

33 minutes ago, Ray Pickle said:

Comparing TFL times up the Ike gauntlet 7.3 vs. 6.6 is not about the engines at all but about transmission tuning choices. The 7.3 ran much closer to its horsepower peak the majority of the run staying between 4200 and 5k for almost the entire run. GM allowed truck to follow more of an economy strategy thus having engine turn between 2600 and 4k way too much of run. Clearly no one with any towing experience would ever so that. I get why they do it for uniformity in testing but it does not offer any insight into real world performance.

Precisely. Most who are towing will lock out upper gears, knowing that keeping the engine around 4000-4500 is where it does it's best work and will pull at that RPM as long as you want or need. I'm not sure the 10-speed would help all that much if the programming is still based for economy.

In my truck at 70 mph in 4th gear is 3000 and 70 mph in 3rd gear is 4000. That being said, I know what gear I need depending on the incline, mountain, etc. to maintain my speed. With most of our camping trips in the flatlands, I just put it in drive and turn on Tow/Haul mode and let it go.

SierraHD17 · February 3, 2020

Once again.. Ford can actually do reasonable transmission tuning and GM... well they use the same transmissions and still can't figure it out. Also nice to see a real rear axle gear as opposed to GM... won't surprise me if they drop to 3.42 when the release the 10 speed. Gm doesn't have a clue.

Can't wait for it and all the guys making spreadsheets trying to show people why they think you don't need the deeper rear end gearing with more transmission speeds. Always a good time.

Edited February 3, 2020 by SierraHD17

Ray Pickle · February 3, 2020

Reasonable transmission tuning? If reasonable, educated, experienced people, where the only ones towing we could agree. But that is not the case. We can both 2nd guess tuning strategy because the 2 manufacturers oppose one anotherk in their approach. But if the G.M. truck would've downshifted, "with different tuning strategy", to 3rd and 2nd if necessary the rear gearing wouldn't have mattered in the least, the times would've been very close. Its amazing how much more intelligent some proclaim to be regarding automotive engineering than those who have a huge staff of automotive engineer specialist who get their marching orders from a fortune 500 company that has been building trucks for over 100 years. Yea they don't have a clue!

TXGREEK · February 3, 2020

Sent from Above

SierraHD17 · February 3, 2020

39 minutes ago, Ray Pickle said:

Reasonable transmission tuning? If reasonable, educated, experienced people, where the only ones towing we could agree. But that is not the case. We can both 2nd guess tuning strategy because the 2 manufacturers oppose one anotherk in their approach. But if the G.M. truck would've downshifted, "with different tuning strategy", to 3rd and 2nd if necessary the rear gearing wouldn't have mattered in the least, the times would've been very close. Its amazing how much more intelligent some proclaim to be regarding automotive engineering than those who have a huge staff of automotive engineer specialist who get their marching orders from a fortune 500 company that has been building trucks for over 100 years. Yea they don't have a clue!

Its pretty straightforward.. if you think reasonable is dropping the engine to sub 3000 rpm with a load on it you are nuts. Gm is too focused on a mpg based strategy and even in "tow haul" that remains true. Ask any engineer with them if that was what they wanted or the directive they were given and the answers will likely vastly vary. The numbers say it all when the competing company keeps their engine in its powerband and best you by 3 minutes with the same load on the same hill with an engine that makes almost identical power. Sure 4.30s in the gm would help but allowing it to drop in rpm that much was the problem... no different than the 6.4 powered Ram they tested a few years ago. But hey.... Gm's awesome factory tuning keeps the aftermarket alive and well.

Edited February 3, 2020 by SierraHD17

Ray Pickle · February 3, 2020

If you actually tow at that rpm under that load you may qualify as crazy. They are obviously emphasizing fuel economy over towing performance in their algorithms. Evidenced by the better mpg posted by tfl in both towing and wmpty testing. I don't necessarily agree with the strategy but I understand why they do it. There are a lot of "bench towing experts"and/or novices who really could not find their backside with both hands and they are protecting their powertrains from potential abuse and warranty expense from those groups. For the rest and the majority we manually select the proper gear/gears for the job. You further assume GM could not tune to hold these gears? Only the aftermarket can?! Funny...

SierraHD17 · February 3, 2020

Yep... And there is still people that think this is an old 350 that will toss a rod at 4 grand of sustained load too... At least you don't agree with the strategy and in the case of a GM truck would likely do as the rest of us would and shift into M to hold a more useful gear...

Edited February 3, 2020 by SierraHD17

dieselfan1 · February 3, 2020

On 2/1/2020 at 11:42 PM, 2016HD said:

I think Mr truck Or should i say mr Ford needs to stop doing the driving!

I couldn't agree more

He's just sitting there steering.

Drive the goddamn thing.

In last year's 6.0 he put the cruise on and let the thing bog down to like 20 mph. Jesus Christ downshift it!

I take TFL with a grain of salt.(you guys should too)

Kind of like what the weather man does for his job.

dieselfan1 · February 3, 2020

1 hour ago, TXGREEK said:

Sent from Above

Oh my.

I can also go buy ($30,000 ish) a 755hp LT4 crate motor and drop it in my Gen V Camaro. With boost though.

You wanna go Bro?

Edited February 3, 2020 by dieselfan1

ShotgunZ71 · February 4, 2020

GM could easily create a transmission flash update that would take effect in Tow/Haul mode to help in this regard. However, I’m in the “put it in M” and I’ll decide how high it shifts. I will say, though, even in D the truck usually stays in 5th on flatlands. I’ve thought about locking out 5th and 6th even then to keep RPM up a little more. Usually not an issue keeping speed on flatlands, though.

dieselfan1 · February 4, 2020

Precisely. Most who are towing will lock out upper gears, knowing that keeping the engine around 4000-4500 is where it does it's best work and will pull at that RPM as long as you want or need. This^^^^^

You could keep that rpm up for hours if you had too. As long as it gets enough air and stays cool.
Not the same motor but in the same motor family I had a 2011 5.3/3.73 6spd that I towed a 8000 lb trailer on a 1650 mile trip out west on some long grades and windy and I ran that thing at 3500- 4200 rpm for at least two hours straight at one point. Never even used 5th or 6th gear at all. [emoji123]
Had to stop and refuel. Temperature gauge never moved. She really likes the fuel at that rpm , I think I got about 5mpg. That thing only had 315hp 338tq too.
Moral of the story is they don't mind running at that rpm one bit. Not one bit.
Pour the coal to it and go.

Sent from my Pixel 3 using Tapatalk

BTW this was not long after Ford came out with their Ecoboost. I remember passing a guy in one on a long 4-5% grade in my 1/2 ton Chevy pulling a big ass trailer and the motor singing along about 3800- 4000 rpm. The look on his face was priceless [emoji23]

C/K Man · February 5, 2020

Looking at the videos, there is a lot to like about the 7.3L. Crank and main caps look good, oil pump/windage tray is clever, big valves and sturdy valve train. Large cooling passages. Head bolts go deep in the block, longer than I originally thought. On the other hand, bore spacing is very tight, head gasket sealing surface is minimal, large front cover has 3 water passages (potential leak paths into crankcase), VVT components appear to be inaccessible unless timing cover removed. Typical Ford, for every good feature you find one questionable one.

At the end of the day you have an engine that compared to the new GM 6.6L gas is a little over 10% larger, produces a little less than 10% more horsepower, and makes essentially the same torque with similar curves.

kenny_r · February 5, 2020

Looking at the videos, there is a lot to like about the 7.3L. Crank and main caps look good, oil pump/windage tray is clever, big valves and sturdy valve train. Large cooling passages. Head bolts go deep in the block, longer than I originally thought. On the other hand, bore spacing is very tight, head gasket sealing surface is minimal, large front cover has 3 water passages (potential leak paths into crankcase), VVT components appear to be inaccessible unless timing cover removed. Typical Ford, for every good feature you find one questionable one.

At the end of the day you have an engine that compared to the new GM 6.6L gas is a little over 10% larger, produces a little less than 10% more horsepower, and makes essentially the same torque with similar curves.

At least the 7.3 in a good looking truck....can’t say the same for the new gm hd’s.lol. There are some things I just can’t look past. I would trust the 6.6 dependability over the 7.3 even though they are equally new.

C/K Man · February 5, 2020

Yes, while the 6.6L is technically new, there really isn't anything in it that has not been in one LS/LT or another.

I like the look of the new GMC Sierra HD's, the Silverado HD not so much........

MTU Alum · February 6, 2020

The 6.6 gas is slower due to engine oil temps. This motor has alot of heat rejection at gcw and high rpms. ECM commands the TCM to stay in higher gear to lower rpms and cool oil temps. You won't be allowed to manually shift around it.