I have a question for some of you veteran travelers concerning which is better on the transmission when driving in hilly terrain.
Do you let the vehicle slow down as you go up hills then pick up speed on the down side to keep the transmission from down shifting, or... do you give it more gas when it starts to slow there by have it down shift and gain the speed back?
thanks
Bob & Deb
W Ma.
04 GMC 1500 4X4, 5.3L
06 Starcraft 18SB
I will let the speed drop if it is just a small hill. Anything larger and I will shift into a lower gear myself. I will not wait for the transmission to do it for me.
This way you can keep the RPMS up where you want them, instead of the engine lugging down, and then the transmission shifting.
moparmaga2 wrote: I will let the speed drop if it is just a small hill. Anything larger and I will shift into a lower gear myself. I will not wait for the transmission to do it for me.
This way you can keep the RPMS up where you want them, instead of the engine lugging down, and then the transmission shifting.
As everyone else has said, let it tell you what it wants. If you have a vacuum gauge, downshift by that versus engine rpm drop as it's faster, more accurate and better for the drivetrain. Bottom line is that you and the vehicle have to work some.
moparmaga2 wrote: I will let the speed drop if it is just a small hill. Anything larger and I will shift into a lower gear myself. I will not wait for the transmission to do it for me.
This way you can keep the RPMS up where you want them, instead of the engine lugging down, and then the transmission shifting.
How does one determine the optimum RPM to keep it at?
moparmaga2 wrote: I will let the speed drop if it is just a small hill. Anything larger and I will shift into a lower gear myself. I will not wait for the transmission to do it for me.
This way you can keep the RPMS up where you want them, instead of the engine lugging down, and then the transmission shifting.
How does one determine the optimum RPM to keep it at?
I would like to know optimum RPM range also. My 5.7 GM makes peak torque at 2,800 RPM's. Does that mean I want to keep it at 2,800 RPM's on hill/mountains? It seems a lot of people are with gassers are towing in the 4,000 RPM range when climbing steep hills. Don't you lose torque when you go above the peak torque RPM's?
Quote: I will let the speed drop if it is just a small hill. Anything larger and I will shift into a lower gear myself. I will not wait for the transmission to do it for me.
This way you can keep the RPMS up where you want them, instead of the engine lugging down, and then the transmission shifting.
That's me...
Quote: would like to know optimum RPM range also. My 5.7 GM makes peak torque at 2,800 RPM's. Does that mean I want to keep it at 2,800 RPM's on hill/mountains? It seems a lot of people are with gassers are towing in the 4,000 RPM range when climbing steep hills. Don't you lose torque when you go above the peak torque RPM's?
That's correct, different engines have their own optimum torque range...You 5.7 is a "mid range" engine, that is it makes it's max torque kind of mid way in the rpm range. The Dodge Hemi and Chevys 5.3 are "revers" that make their max torque at around 4000 rpm and are designed to run in that rpm range when needed to.
You are also correct in stating that reving an engine past it's max torque rpm means the torque actually starts dropping...but most of the time when an engine is running those rpm's the trucks in a lower gear to get the mechanical leverage it needs to climb a hill...a gear low enough that the truck can pull up the hill with less then the max rated torque needed, but the extra rpm is now used to keep up a desired speed.
In other words, when you drop your truck down to 2nd gear to climb, you don't need full throttle because the gear is so low, but if you want to tow faster you give it more throttle and rpm...
To answer you original question about you 5.7L, I wouldn't run it at 4000 rpm or more for any length of time...
I'm sure I'll hear replies on that one...
* This post was
edited 05/31/08 07:48pm by loufish *
"I won't camp next to you, if you don't camp next to me!"
2004 Titan King Cab, 2wd, 5.6L V-8, 5 Speed Auto Trans, Tow Package.
2004 Jayco Qwest Baja P/U
I'll back out of it on any hill where I know there's a possibility of the transmission staying in 4th/lockup if I do so, but then again I'm a diesel guy so letting it work down into it's torque curve is beneficial versus downshifting and letting it roar up the hill on horsepower alone.
If there's zero chance of it pulling a grade without downshifting then I'll usually still back out of it anyways until the downshift occurs, and then put my foot into it to maintain whatever speed it downshifted at.
I could leave it on cruise control and maintain highway speed up allot of grades, but it costs more fuel, and I'm seldom in that much of a rush. If someone else wants to tear by me at 75MPH getting 2MPG up a grade while I pull a grade at 55MPH and get three times that, then all the power to them - I'll be passing them again at the next fuel stop.
* This post was
edited 06/01/08 09:08am by PrivatePilot *
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