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 > Ideal V8 rpms when towing?

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Siletzspey

Shedd, OR

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Posted: 10/08/19 12:31pm Link  |  Quote  |  Print  |  Notify Moderator

My F350 SRW 4x4 with 6.2L gas has a 3.73 axle and 18" tires. I carry a 9'6" NL truck camper which puts me at about 11,000lbs total.

When cruising at 70mph, I turn 1,800rpms in 6th gear, and 2,300rpms in 5th gear. On a mild up slope the engine seems fine in 6th at 1,800rpms (e.g. I don't get any odd sound or sensation of lugging).

Is there any thought on what a good rpm is for the engine and transmission when towing a load? With my prior 1997 Ford Expedition, the TOW button would disable the highest gear (OD).

I also plan to upgrade to a slightly larger 18" tire so I can go from 3,640 to 4,080lbs per tire, and estimate 6th gear will drop to 1,700rpms, and 5th to 2,200rpms. I wonder if I will want to purposely avoid 6th?

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2oldman

New Mexico

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Posted: 10/08/19 12:41pm Link  |  Quote  |  Print  |  Notify Moderator

1800 rpm seems about right.

jimh425

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Posted: 10/08/19 12:45pm Link  |  Quote  |  Print  |  Notify Moderator

No idea what ideal might be, but 1800 seems pretty low if you can do it. Lower is generally better MPG, and I doubt that the electronics will let you go lower than you should.

One thing to consider is a tuner. Then, you’ll have more control over shift points and can update your speedometer to work with the bigger tires. But, it might be possible that a slightly larger tire just makes your speedometer dead on.


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RCMAN46

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Posted: 10/08/19 12:53pm Link  |  Quote  |  Print  |  Notify Moderator

Install a vacuum gauge. With a gas engine the vacuum will give you an indication if you are lugging the engine. Go with the gear that will give the best vacuum.

noteven

Turtle Island

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Posted: 10/08/19 01:09pm Link  |  Quote  |  Print  |  Notify Moderator

My 6.2 F350 in carry the camper mode runs same rpm as OP said. If head or cross wind has it shift from 6 to 5 a lot I select to limit top gear to 5. It sometimes choose gear 4 and runs along at 2500 rpm for miles. It never sounds like it is “lugging” or frantic, seldom revving above 3500rpm unless you apply lotsa throttle. This is on 87 E10 gas.

This would be a super fun engine if it had “EcoBoost” stuff.

The cruise control allows more mph drop before downshift than I like. I can get it to hold speed and not shift in manual throttle mode.

I’m going to try some 91 gas once I get road tripping. A friend tows with a 5.4 Ford and the engine management likes 91.

time2roll

Southern California

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Posted: 10/08/19 01:12pm Link  |  Quote  |  Print  |  Notify Moderator

I usually recommend close to the rpm associated with the peak torque rating.
Maybe a little lower if lightly loaded and a little more if running heavy.


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Grit dog

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Posted: 10/08/19 01:12pm Link  |  Quote  |  Print  |  Notify Moderator

^ Or don’t worry about it. If the engine can’t pull it, it’ll downshift. If the downshifting gets annoying in the hills, lock out 6th.
To the OP, just put it in tow haul (or don’t, won’t hurt anything either way) and drive.
Your mpg will be about 90% dependent on speed, wind, aerodynamics and hills and about 10% on which gear you pick.
Personal preference, I prefer higher rpms with a bit more throttle response. But again, shift it into D and enjoy the scenery.

Edit. The ^ was to the vacuum gauge suggestion.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

Kayteg1

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Posted: 10/08/19 02:31pm Link  |  Quote  |  Print  |  Notify Moderator

Observing engines efficiency was always my hobby and also boredom killer when I cover long distance.
Each engine has it "sweat spot" and you have to find it on your own as no publications will give you that.
Modern engines pull strong at 1000 rpm, while 1200 rpm gives them good torque for hills climbing.
I am talking diesels in case you did not notice [emoticon]
My 6.7l Powerstroke cruise 60 mph at 1600 rpm and it is good for pulling 8000 lb trailer on 14 miles steep grades I am facing whenever I go on West Coast.
I can only wish I could get lower differential ratio as after all those years of playing with gears, now pulling heavy set on steep grades without downshifting just doesn't sound right.
With gasoline engine you have to observe pinging. Modern engines will adjust timing to protect the engine, but that leads to less power, gear shifting and whole Hell break loose.
When I was driving gasoline car - going across Sierra I always filled with Premium to avoid the hassle.





Bob Shaw

Newnan Ga

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Posted: 10/08/19 02:55pm Link  |  Quote  |  Print  |  Notify Moderator

Torque, rpms, sweet spot... it all sounds great, right? Try this try towing your trailer over the same route at different speeds, and see how much your fuel mileage changes at the different speeds. Then pick the speed/fuel mileage you can live with. You'll be surprised how fast your fuel mileage drops the faster you go. When I was working, I was in a hurry, and towed at 75 mph and used to get 4.5 - 5.5 mpg. After I retired, I tried slowing down to 62-65 mpg and my fuel mileage climbed to 8.5 - 10 mpg. I guess I'm not in that much of a hurry any more.

NRALIFR

Truck Camping Out West

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Posted: 10/08/19 03:44pm Link  |  Quote  |  Print  |  Notify Moderator

I think mine is at the right rpm when it goes “bubbita bubbita bubbita bubbita bubbita..........”.

Just like that. Puts the boss to sleep. [emoticon]

[emoticon][emoticon]


2001 Lance 1121 on a 2016 F450


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