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Discussion Starter · #1 ·
2009 Sonata I4
I've noticed that while in cruise control any hill causes the transmission to downshift two gears, 5th to 3rd. Is this normal or should it go down to 4th unless it's a very steep hill?
 

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As the owner of a manual transmission Sonata I can't say what's normal for an automatic Sonata, but I may still be able to help with your question. My minivan will do the same thing. First the torque converter unlocks, which is good for a 300 rpm increase. If that's not enough, it will downshift from fifth to fourth gear (about 3,100 rpm at 70mph). And if that isn't enough, it will downshift to third (about 4,200 rpm at 70 mph). When fully loaded and travelling through mountains, the cruise control will use third regularly. (It is sometimes annoying.) If drive without cruise but maintain exactly 70 mph up hills, it will still downshift to third. However if I drive without cruise and let my speed slip just a few mph, like from 70 mph to 68 mph, it will not downshift. Like the Sonata, my minivan engine gets its peak torque at 4,000 rpm. If the engine is asked to work hard, that's where it wants to be. (It certainly won't hurt the engine.) Based on my car, I'd say it is normal. But if no one confirms what is normal for an I4 Sonata, you can always check with your dealership.
 

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I don't know if this helps, but I live in West Virginia (the Mountain State), and at the slightest hint of a hill when the cruise is on, my car (pretty much the same as yours) immediately goes to fourth, then to third. If you live in a more mountainous region, what you are experiencing may be normal, but if you live in a "normal*" area, you may want to have your **** looked at.

*not a major North American mountain range.
 

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Discussion Starter · #5 ·
Thx for the responses. I'm talking about moderate hills, like going over an overpass. I'll be in cruise at 110kph at 2200rpm and it instantly goes to 3000rpm. Feels like the kickdown is a lot more sensitive in cruise control. Engine is allowed to work a lot more out of cruise before a downshift occurs and out of cruise it'll go to 4th(2600rpm) and not directly to 3rd. This is with an unloaded car.
Does anyone know if the cruise control is adjustable? I've had manuals before and the inclines I'm talking about wouldn't be long or steep enough to require a downshift.
 

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I can only guess when saying this sounds normal. In several cars I've driven in the past (rented included), when my foot was resting (just touching, not pressing) on the gas pedal, whenever I would tap the Cruise Control just slightly to accelerate, I would notice the gas pedal traveling down significantly, and the acceleration well noticed. Nowadays, on long trips, whenever I use then CC driving my Sonata, I leave my foot resting aside, so I'm not sure, but I'm guessing your/my/our Cruise Control is behaving similarly....
 

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QUOTE (Pierre @ Jul 18 2010, 08:30 AM) index.php?act=findpost&pid=342630
Thx for the responses. I'm talking about moderate hills, like going over an overpass. I'll be in cruise at 110kph at 2200rpm and it instantly goes to 3000rpm. Feels like the kickdown is a lot more sensitive in cruise control. Engine is allowed to work a lot more out of cruise before a downshift occurs and out of cruise it'll go to 4th(2600rpm) and not directly to 3rd. This is with an unloaded car.
Does anyone know if the cruise control is adjustable? I've had manuals before and the inclines I'm talking about wouldn't be long or steep enough to require a downshift.
This may have no direct relevance to the cruise control, but based on your numbers it sounds like your car doesn't downshift to third. It only goes to fourth gear. If it hit third gear, the rpm would exceed 4,000 rpm at 110kph (69 mph). It is very likely the first jump from 2,200 rpm to 2,600 rpm was the torque converter unlocking. Even though the rpm increased by 400, it was still in fifth gear. It didn't downshift yet. However the jump from 2,600 rpm to 3,000 rpm at 110kph sounds like a downshift from fifth gear to fourth gear. (I base that on the mathematics of the gear ratios.) You might find that to be good news. It seems like your transmission is not bouncing around that much at all. It is only dropping one gear.

I agree 100% with Mamania's cruise control comment. When I operate the cruise, sometimes I lightly rest my foot on the pedal to monitor how much the computer depresses the gas pedal as the car goes up hills. Sometimes the gas pedal moves a couple inches. That would explain, or at least be consistent with the transmission's need to downshift. As mentioned before, when I drive my minivan fully loaded (wife, two kids, full gas tank, and A LOT of luggage) it will downshift all the way to third (4,000+ rpm) going up steep hills. So Pierre, if your car only downshifts to 3,000rpm at 110kph, that's minimal.
 

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Discussion Starter · #8 ·
I guess what you're saying makes sense. So there's about 400rpm of slippage with the torque converter unlocked. Didn't think of that. The cruise control appears to have a very small deadband because the speedometer doesn't budge. Was expecting to hear a bit of work out of the motor before a downshift but I hear no change. Also expecting a bit of speed loss, may be a good thing if there isn't any!
 

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It is downshifting to 4th as mentioned above.
You can double check by pushing the shifter briefly to the right (shiftronic mode) and read which gear it's in on the dashboard.

I often leave the car in shitronic mode so it doesn't downshift to 4th with the cruise control.
 
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