Towing...what gear/RPM is best? - Page 2 - Fiberglass RV


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Old 04-27-2014, 10:37 PM   #15
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Does the fact that I have 175k on the odometer matter here? I seem to be getting the impression that 4th is the way to go, generally...
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Old 04-28-2014, 01:04 AM   #16
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I have had and driven a 27' Class A and a 24' Class C motor home and they both had automatic transmissions. The only time I used the Overdrive, the setting that lets the motor run the slowest, was either downhill or on the level. You can do the same, it is easier on the engine. At 175k miles on the engine, keep the oil changed and be kind to the engine.
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Old 04-28-2014, 06:50 AM   #17
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Folks, part of the reason to run a higher RPM is to protect the transmission. Less stress on gears.
More research would be needed to find out how stout his tranny is.

PS.... Mike "(Example: when my uncle blew my dad's Model A engine by trying to climb Pike's Peak in top (3rd) gear.)"

Cool.... I have read about the climb many times. Wow!
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Old 04-28-2014, 11:38 AM   #18
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I am towing with a 2003 manual 4cylinder subaru forester. The only mention the manual makes about recommended gears and towing that I can find is the statement: "...if your vehicle is equipped with an automatic transmission, avoid driving with the gear selector lever in 'D' when towing a heavy trailer to prevent fluid overheating. A lower gear should be used."

I have experimented with driving the same route in both 4th and 5th (philly to assateague) in the same direction so that prevailing winds are at least similar if not identical, and have found MPG to be measurably better when using 5th and therefore lower RPMs the whole (mid-atlantic coastal, flat) way.

I'd like to hear more about this higher RPMs = less engine stress business. Dumb it down for us non-gearheads please!
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Old 04-28-2014, 12:58 PM   #19
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Originally Posted by jen b View Post
I'd like to hear more about this higher RPMs = less engine stress business. Dumb it down for us non-gearheads please!
Think about going up a hill on a 10 speed bike. If you drop down to a lower gear you pedal faster to keep up the speed but you can make it up the hill without much effort. Keep it in a higher gear and it is a lot of work.

Every engine has an optimum RPM for power output (called a torque curve when graphed out) Torque - Wikipedia, the free encyclopedia

I once had a 69 Chevelle with a 2 speed powerglide transmission. Dropped a 350 LT-1 into it with a high lift cam and a few other goodies. It sounded mean. It would almost stall out trying to do a fast take off from a stop. A lot of work at low RPM's. Put the pedal to the metal at anything over 50 MPH and it would leave most other vehicles behind. Lots of power at the higher RPM. No good on the 1/4 mile drags, but great on the ovals.
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Old 04-28-2014, 01:48 PM   #20
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The Flex comes with a 6 speed automatic. If you select "sport" it enables a more aggressive shift pattern and limits it to 5 speeds. This mode is suggested in the manual if the transmission shifts too much while towing in the 6 speed mode. Last year I went to one of the Indiana get togethers in "Sport" and came back in the 6 speed mode. In "Sport", at my 65 MPH cruising speed I ran about 700-800 RPM higher than the same speed in 6 speed mode. Miles per gallon turned out the same either way. So I'm returning to my normal procedure which is what the manual recommends for my vehicle. 6 speed mode in the flatlands, 5 speed when I notice the transmission "hunting" a bit.
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Old 04-28-2014, 04:53 PM   #21
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If terrain is rolling hills or involves long stretches of even gradual uphill you may find yourself downshifting to maintain power. If you have to shift more than you want to shift stay in a lower gear. Adjust speed.

Going down hill shift up to improve fuel economy. That is if you don't need the engine and lower gear to prevent picking up too much speed (engine braking) on the down hill.

Whole point of having that many gears is to allow engine to spend more time in the "sweet spot" of it's power output.

Automatics with overdrive have an OD off feature in part because the slight push/pull of the trailer from minor changes in throttle, bumps or small brief changes in up/down grade of road can cause the transmission to keep shifting back and forth between OD and next gear down. Hard on the transmission to shift back and forth in highway gears.
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Old 04-28-2014, 04:55 PM   #22
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Think about going up a hill on a 10 speed bike. If you drop down to a lower gear you pedal faster to keep up the speed but you can make it up the hill without much effort. Keep it in a higher gear and it is a lot of work.
As a bike rider I understand what you are saying Roy. Perhaps that is another reason why I like to stay out of the low RPM range when towing.
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Old 04-28-2014, 08:26 PM   #23
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Rpm

I just thought of something while reading this post.

A good indication of how the engine likes the gear ratio.

With the trailer connected and running down the road put the transmission in 4th gear and push down on the gas pedal for 4 or 5 seconds and watch the speedometer, noting an increase in speed.

Next try the same thing in 5th gear and note the speedometer change.
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Old 04-28-2014, 09:09 PM   #24
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With my '05 2.7 5 speed tacoma, I never use 5th gear when towing, 4th gear is good up to about 85 mph. WAY faster than I drive anymore. Let the RPM's do the work, these engines are not made for low end torque
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