Normal cruise control speed variations?
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Senior User
Joined: Mar 2004
Posts: 115
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From: Central WI
Normal cruise control speed variations?
Does anybody else have an issue with the speed dropping 3-4 MPH while on cruise? I have had this happen under light loads and with all the power available I would think it would hold the speed better.
Senior User
Joined: Nov 2003
Posts: 284
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From: WV
I have the same issue, but mine is all the time. I have set it on 70 mph, and look down and be running 74 to 75 mph. And also happen the other way 4 to 5 mph slower. this is on flat land also. I notice it does do it alot worse when i am in West Virginia. Don't know what it is.
My company truck which is a 3/4 ton chevy doesn't do this even with on of our big generators on the back. Just thouht it was normal operation for the 6.0, but it is frustrating.....
PSDboy
My company truck which is a 3/4 ton chevy doesn't do this even with on of our big generators on the back. Just thouht it was normal operation for the 6.0, but it is frustrating.....
PSDboy
Post Fiend
Joined: Oct 2002
Posts: 11,314
Likes: 4
If you are in hilly terrain, cruise is the least effecient mode for your mpg....
the engine typically will coast, then accelerate hard uphill-
and that happens with any vehicle short of those with the laser predictive cruise setups that anticipate a hill and accelerate before it....
Even if you use cruise, u might get into the habit of accelerating slightly to give a slower fuel usage to "get ready" for the hill so you're accelerating on the flats and not on the uphill....
Much betta for your mpg !
the engine typically will coast, then accelerate hard uphill-
and that happens with any vehicle short of those with the laser predictive cruise setups that anticipate a hill and accelerate before it....
Even if you use cruise, u might get into the habit of accelerating slightly to give a slower fuel usage to "get ready" for the hill so you're accelerating on the flats and not on the uphill....
Much betta for your mpg !
Got Diesel?
Joined: Jan 2004
Posts: 4,345
Likes: 22
My March 2003 6.0 holds just fine on cruise control.
As Ron Propeel says about his cooking machine "Set it and forget it!"
I am running the most recent flash for my March 2003 truck (December 2003 flash)... if that makes a difference for anyone.
Thanks,
Jeff
As Ron Propeel says about his cooking machine "Set it and forget it!"
I am running the most recent flash for my March 2003 truck (December 2003 flash)... if that makes a difference for anyone.
Thanks,
Jeff
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Posting Guru
Joined: Nov 2002
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From: Texas
My '04 doesn't vary the speed on level surfaces, but when climbing a hill, it will lose mph slowly, then pour the coal to it--much less effecient than using my foot. Its really not a problem to me, and I just don't use it in hilly terrain. The cc in my old '02 V10 was much more constant in all types of driving--BUT, I don't want it back just because the cc operated better.
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Senior User
Joined: Apr 2004
Posts: 379
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From: hillsborough NJ
Originally Posted by jdadamsjr
If you are in hilly terrain, cruise is the least effecient mode for your mpg....
the engine typically will coast, then accelerate hard uphill-
and that happens with any vehicle short of those with the laser predictive cruise setups that anticipate a hill and accelerate before it....
Even if you use cruise, u might get into the habit of accelerating slightly to give a slower fuel usage to "get ready" for the hill so you're accelerating on the flats and not on the uphill....
Much betta for your mpg !
the engine typically will coast, then accelerate hard uphill-
and that happens with any vehicle short of those with the laser predictive cruise setups that anticipate a hill and accelerate before it....
Even if you use cruise, u might get into the habit of accelerating slightly to give a slower fuel usage to "get ready" for the hill so you're accelerating on the flats and not on the uphill....
Much betta for your mpg !
Senior User
Joined: Mar 2004
Posts: 394
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From: s.f. bay area
I recall reading in another thread last week about a new flash for the 04 trucks that improved the cruise control operation after coming down a hill and having the truck undershoot the desired speed, and then pour on the diesel to get back to speed. I have experienced this myself coming down a hill with 8000 lb trailer on the back. Note this isn't a slow down approaching an uphill, but a bad undershoot recovering from a higher the desired speed from a downhill run.
Post Fiend
Joined: Oct 2002
Posts: 11,314
Likes: 4
Oh, that is a different problem n6nfg...
I could see where the tolerances could be adjusted for that via computer tweaking...
but alfama - there are cruise controls that do anticipate the hills and do just that slight acceleration....
not sure how they work, but always thought that was neat...
wonder how it does when a truck is in front of it so it doesn't "see" the hill !?!
I could see where the tolerances could be adjusted for that via computer tweaking...
but alfama - there are cruise controls that do anticipate the hills and do just that slight acceleration....
not sure how they work, but always thought that was neat...
wonder how it does when a truck is in front of it so it doesn't "see" the hill !?!
New User
Joined: Jun 2004
Posts: 18
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From: southeast Texas
I can second the "bad undershoot" of the cruise to recover coming down a hill. My 04 has done it 2 to 3 times running w/o a load. Aside from a few instances I'm very pleased with the cruise and the truck my first 9000 miles.
Originally Posted by n6nfg
I recall reading in another thread last week about a new flash for the 04 trucks that improved the cruise control operation after coming down a hill and having the truck undershoot the desired speed, and then pour on the diesel to get back to speed. I have experienced this myself coming down a hill with 8000 lb trailer on the back. Note this isn't a slow down approaching an uphill, but a bad undershoot recovering from a higher the desired speed from a downhill run.
Senior User
Joined: Apr 2004
Posts: 379
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From: hillsborough NJ
i had a vehicle that it would actually downshift to a lower gear when it was going down hill. to slow it down, the first time it did it i was completly unprepared for it so it was surprising