LIKE2BUILD wrote: Typically I don't like to use it on my truck while towing in OD because the cruise control on GM vehicles is very aggressive. The slightest drop in speed (say from 62MPH to 58MPH) will cause it to shift from 4th down to 2nd gear and then back to 4th when the set speed is regained.
KJ
I noticed that GM's 6.0L gasser does have a more aggressive shift feel to it when going up hill with a heavy load in the back. Then I noticed with a brand new 6.6L Diesel and a similar heavy load, the shifting is less frequent up hills and the transitions from down shifting is a whole lot smoother. The diesel tranny shifting is minimal and I can stay in 5th or even 6th gear with no problems.
I believe it's because the diesel engine produces more torque than the gasoline engine, therefore making shifting with a load behind it more managable and there is less "searching" for gears when going up hill. I noticed that the tranny on my diesel can stay in 5th or even 6th gear and it doesn't need to downshift as frequently as my gasser did.
So, I may be looking at this all wrong, but what is the difference between your foot maintaining speed going up a hill and the cruise control maintaining speed going up a hill? I can understand steep up / down hill, but outside of that and slick roads....why not?
Rick & Joan
Rogers, Arkansas
2005 32ft Jayco Eagle TT
2005 GMC Sierra 2500HD
JaycoRickJoan wrote: So, I may be looking at this all wrong, but what is the difference between your foot maintaining speed going up a hill and the cruise control maintaining speed going up a hill?
None really, except that cruise control will typically be more steady and therefore to some degree return a better fuel economy.
I use it when I can, but there are times (like the OD interstate example I gave) where my foot can be more efficient than the rapid jump to 2nd gear. AirSupport is right, the factor is torque and on the 6.0L gasser, the tranny is trying to hit peak torque and stay there for the acceleration. However, with my foot and "easily" allowing the tranny to drop into 3rd, I can gently accelerate back up to my desired speed.
LIKE2BUILD wrote: Typically I don't like to use it on my truck while towing in OD because the cruise control on GM vehicles is very aggressive. The slightest drop in speed (say from 62MPH to 58MPH) will cause it to shift from 4th down to 2nd gear and then back to 4th when the set speed is regained.
KJ
I noticed that GM's 6.0L gasser does have a more aggressive shift feel to it when going up hill with a heavy load in the back. Then I noticed with a brand new 6.6L Diesel and a similar heavy load, the shifting is less frequent up hills and the transitions from down shifting is a whole lot smoother. The diesel tranny shifting is minimal and I can stay in 5th or even 6th gear with no problems.
I believe it's because the diesel engine produces more torque than the gasoline engine, therefore making shifting with a load behind it more managable and there is less "searching" for gears when going up hill. I noticed that the tranny on my diesel can stay in 5th or even 6th gear and it doesn't need to downshift as frequently as my gasser did.
I have an 04 Dmax. Shifting depends on your load, and load is relative. Same load behind the 6.0 gas and the Dmax, of course the Dmax shifts less. A larger load behind the Dmax and it shifts frequently also........way to much if you ask me. On cruise this truck does not hesitate to run 3000 in 4th on slight (IMO) inclines, GM cruise does not want to give up those mph.
JaycoRickJoan wrote: So, I may be looking at this all wrong, but what is the difference between your foot maintaining speed going up a hill and the cruise control maintaining speed going up a hill?
Many RV'ers (subconsciously or often intentionally) let up pressure on the accelerator while climbing hills to avoid a downshift.
I know that I can use CC comfortably with my setup, but if I get into a hill and leave it engaged it can catch you off guard when the tranny slams down a gear in an attempt to maintain the speed. When not using cruise control you maintain a steady pressure on the accelerator which will allow the vehicle to slow while maintaining the gear - the CC simply presses harder and harder until it forces a downshift.
Milage can be better in the flats while on CC if the vehicle can maintain the gear, but using CC on the hills where its constantly hunting for gears can actually negatively effect milage since it causes the engine to work harder for brief periods, whereas a light foot could simply bleed hill-climbing speed for fuel efficiency instead.
So, the answer to the original question is yes and no, depending on terrain.
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