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Wasn't sure how to title this to attract attention to the strange issue. Just wondering if someone has an explanation.

The situation: 2.0 engine, auto 4 (2011) Soul. I find the car drops too quickly into 3rd gear on moderate hills while in Cruise, when it seems the engine still has power to make the climb in 4th. This results in the usual sudden high rpms, downshift, noise, etc., and the fellow beside you thinking you want to race. Annoying. So, I have often shifted the trans over to manual shifting mode, and left it in 4th gear (this stops it from shifting, even in cruise, until things get drastic, I presume, which they don't.... easily handles almost all hills w/o needing to manual shift).

Now, at highway speed (in cruise), the engine is turning over about 2700 rpm. As the engine comes under load, it will take a jump up about 300 rpm more and gain some added power. It's still in 4th gear, and maintaining the same speed. When the load eases as I reach the crown of the hill, the rpm's will drop back to 2700 again. It's not a gradual thing, it does it in one action. It's not a shift into 3rd, which is far more dramatic, and the dash indication stays at 4th gear. So what is taking place with this rpm increase? And how is it being managed, considering that the car speed does not increase with it? Is there a torque converter lockup or the like that is being released at that load point, allowing some excess rpm's to be lost in the converter? Explanation?

This is nothing new, always performed this way, not really an indication (I hope) of anything wrong, just seems to be the way the engine/trans is being managed by the computer(s). But I don't see how an increase in rpm of about 300 is being absorbed into the system, providing a boost in power, of course, but no increase in car speed. (Our last car was a Caliber with a CV (constant velocity) transmission.... this behavior was normal there, as the rpm's rose on the hills while the car speed remained the same... can't see how it happens in a conventional transmission, however, as there should be little variance in the rpm vs car speed in a given gear (4th). This isn't a slippage of random rpm's, this is a very definite raise of an exact amount in response to load, and a drop back to the normal rpm's after load.

Anyone with some significant mechanical knowledge know if my practice of shifting into manual for this purpose might have any potential for any damage? Don't want an opinion here off the top of your head if you aren't familiar with the mechanics of automatic transmissions. I downshift if the hill is too steep and I feel/hear the engine go under too much load. For most hills in my not remotely mountainous area, the engine is quite capable of handling things in 4th.

Anyone have an explanation for this rpm increase? Thanks. :think
 

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Most likely the torque converter clutch releasing which causes a loss in the efficiency of power transfer between the engine and transmission causing the engine rpms to increase to maintain the same speed.
 

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Yep, your torque converter is definitely unlocking to provide some extra horsepower in the upper RPM band. However, I would say that leaving it in the automatic mode is much better while going up a gradual incline rather than forcing it to stay in fourth. 2700 cruising RPMs while going up a hill is pretty low for a 4-cylinder engine.

I realize that while that spike in RPMs from 4th to 3rd is drastic and slightly annoying, it's better for your engine in the long run.
 

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Yep, your torque converter is definitely unlocking to provide some extra horsepower in the upper RPM band. However, I would say that leaving it in the automatic mode is much better while going up a gradual incline rather than forcing it to stay in fourth. 2700 cruising RPMs while going up a hill is pretty low for a 4-cylinder engine.

I realize that while that spike in RPMs from 4th to 3rd is drastic and slightly annoying, it's better for your engine in the long run.
So, what do you think of using the OD lockout button on the 4 spd in the mountains? Heading for the Rockies soon.
 

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I was born and raised in the Rockies in Montana. The rule of thumb over long-painstaking mountain passes, is if your car goes from OD and downshifts, gains speed, then goes back into OD, then repeats the process, Just shift into the lower gear and stay there. This prevents the switching back and forth and keeps the car at one speed and RPM.

It's much safer for you, and the drivers around you keeping a constant speed, plus in the winter, the last thing you want is drastic torque shifts so you don't spin out.
 
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