Cruise Control Issue
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Cruise Control Issue
Hey everyone. I have a question...and I am not sure if its me or not so I am needing some feedback.
While cruising down the WV turnpike on the way to the Daytona 500 I have the cruise set at 70 or so MPH and I noticed a few times that as you would get to the bottom of a small downhill grade and just as the truck would start to go up the next one, their would be a little "jerking" sensation as if they truck was trying to "miss" just ever so slightly. The RPM's never moved off 2135 the entire event...this happened only a few times.
I could watch as we went down the long grades on the turnpike the boost would go down to almost 1 or nothing and then as we started up and the boost gauge just started to show some activity, it was like the truck had to catch up with itself.
Is this normal for cruise control behavior when going up and down long grades like the WV Turnpike for example. Never really noticed it much else except their. And can't remember if I have ever run into that before or not...doesn't ring a bell but then again, not sure.
Thanks for the thoughts,
RC
While cruising down the WV turnpike on the way to the Daytona 500 I have the cruise set at 70 or so MPH and I noticed a few times that as you would get to the bottom of a small downhill grade and just as the truck would start to go up the next one, their would be a little "jerking" sensation as if they truck was trying to "miss" just ever so slightly. The RPM's never moved off 2135 the entire event...this happened only a few times.
I could watch as we went down the long grades on the turnpike the boost would go down to almost 1 or nothing and then as we started up and the boost gauge just started to show some activity, it was like the truck had to catch up with itself.
Is this normal for cruise control behavior when going up and down long grades like the WV Turnpike for example. Never really noticed it much else except their. And can't remember if I have ever run into that before or not...doesn't ring a bell but then again, not sure.
Thanks for the thoughts,
RC
Go Bills !
Joined: Jan 2008
Posts: 2,778
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From: Buffalo, NY
Subscribing.. When i was on the thru way i felt it once with the camper. Truck empty on the way home from Florida it happened a couple times.. My heart stopped thinking something was wrong for that couple seconds.. It was slight but i noticed it. I was thinking/guessing it had to do with the turbo. Curious to what others will say. It rarely happens so it is tough to nail down. I might have only felt it 5 times the entire time i owned the truck.
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Danskool....interesting. I have had the CPS recall and that is replaced. Oil was new pre-trip. The only thing that is not changed out lately was the fuel filter. I am going to do that as soon as the outside temp allows me to be outside. It is 12 here so maybe this coming weekend.
Yeah I agree...rarely. I don't think that I noticed it anymore or maybe but once or twice the rest of the trip....interesting indeed!!!
Yeah I agree...rarely. I don't think that I noticed it anymore or maybe but once or twice the rest of the trip....interesting indeed!!!
Senior User
Joined: Nov 2006
Posts: 174
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From: Raleigh, NC
I've had a little jerking while going on a slight downhill grade before. It's like the truck can ALMOST maintain the speed it's set at from gravity, but then the cruise gives it some gas, decides it doesn't need it, then turns it back on, and so on.
Never had it happen uphill before, though....
Never had it happen uphill before, though....
Laughing Gas
Joined: May 2007
Posts: 1,100
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From: Davis, Ca.
I would think the trans may be searching a little on cruise going down hill, a good enough of a grade and your truck can coast and maintain a speed. I have done this many times while not on cruise, but I am able to controll the throttle myself, and if I give it some throttle trying to maintain a certain speed I will get a little buffeting like the trans is looking for the correct gear. A figure this is from the lower rpm's at a given speed since you are basically coasting. The manuals do recomend not using cruise in the hills.
Cargo Master
Joined: Mar 2006
Posts: 2,502
Likes: 2
From: Bend Oregon
is it maybe the TC going from free to locked when the motor comes back from idle? I used to feel this before I installed the tugger kit in the tranny, It keeps the TC locked longer to aid in maintaining speed down hill while towing; I haven't noticed the described clunk since then.
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Elder User
Joined: Dec 2009
Posts: 864
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From: Fort Campbell, KY
Drive line slop / back lash. I have a Detroit locker, and that behavior is VERY pronounced. Speed is read from the VSS (mounted on rear ring gear) and adjustments are made to fueling as PCM/GEM (not sure which) compares the actual speed to the desired speed and makes corrections.
If your truck is "chipped" the factory corrections will be "more juice" than needed, causing to much acceleration, at which time the computer pulls back on the coals. On slight down hills, this phenomena is exacerbated by the ease at which the truck can accelerate. If the hill is steep enough, no problem because you maintain a speed higher than called for. Same with up hill, you need constant coal to maintain.
May want to chalk the wheels, place in neutral, and see how much play you have in your drive shaft. May be the sum total of a few things (little slip yolk, little on the back lash, maybe a U-joint checking out) you get the idea.
If your truck is "chipped" the factory corrections will be "more juice" than needed, causing to much acceleration, at which time the computer pulls back on the coals. On slight down hills, this phenomena is exacerbated by the ease at which the truck can accelerate. If the hill is steep enough, no problem because you maintain a speed higher than called for. Same with up hill, you need constant coal to maintain.
May want to chalk the wheels, place in neutral, and see how much play you have in your drive shaft. May be the sum total of a few things (little slip yolk, little on the back lash, maybe a U-joint checking out) you get the idea.
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Posting Guru
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I do have a new tranny that is not in my signature. It is a heavy duty tranny with a bigger cooler. I can feel it shift different at take off than the old one being a little bit firmer. But I have always had a little "clunk" just after starting out that I was always told it was a little slip which seems common.....
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Thanks for the info guys. I look forward to reading some more as people post!!! Guess I am not the only one to have noticed then....
