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  #1  
Old 06-27-2012, 09:15 PM
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First gear mystery

Ok, I admit that I have an obsession for how things work, but I don't understand automatic transmissions. If I put mine into first gear and start up a steep hill, I assume that I am in first gear and it will stay there. However, when I reach a point where the hill starts to level off, I noticed that something inside has just downshifted - as I see and hear a 300-400 RPM drop. So what's going on? Is first gear really two different ratios?
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Old 06-27-2012, 11:25 PM
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Re: First gear mystery

don't drink and post my friend
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Old 06-28-2012, 12:03 AM
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Re: First gear mystery

If you are observing this while holding first gear, then it's likely the torque convertor lock up clutch engaging. With the clutch unlocked, the torque convertor allows a speed difference between the engine and the transmission but when it locks the engine speed will drop and match the speed of the transmission.

It can sound like it has changed up a gear.
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Old 06-28-2012, 12:30 AM
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Re: First gear mystery

Most excellent. Off to study torque converters next...
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Old 06-28-2012, 01:35 AM
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Re: First gear mystery

Here's an explanation of how this transmission works. Unfortunately doesnt show the torque converter...

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Old 06-28-2012, 05:45 AM
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Re: First gear mystery

you can't really read a general article on transmissions and expect it to apply here. Dodge transmissions are retarded and don't really follow any normal rules.

Your Jeep probably shifted into overdrive going up the hill at a slow speed and then finally realized it was in the wrong gear and then downshifted.

If you can't tell, I hate the transmission in my Jeep.
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Old 06-28-2012, 06:32 AM
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Re: First gear mystery

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Originally Posted by DanS View Post
Ok, I admit that I have an obsession for how things work, but I don't understand automatic transmissions. If I put mine into first gear and start up a steep hill, I assume that I am in first gear and it will stay there. However, when I reach a point where the hill starts to level off, I noticed that something inside has just downshifted - as I see and hear a 300-400 RPM drop. So what's going on? Is first gear really two different ratios?
If the rpm's dropped at a constant mph, then that would be an up shift, not a down shift.
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Old 06-28-2012, 06:59 AM
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Re: First gear mystery

Guys ... DanS did state that he put the transmission into first gear. So it's not in Drive, and cant up or downshift.
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Old 06-28-2012, 11:46 AM
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Re: First gear mystery

Quote:
Originally Posted by savvas View Post
Guys ... DanS did state that he put the transmission into first gear. So it's not in Drive, and cant up or downshift.
So??? The transmission isn't smart enough to shift correctly let alone limit gears and some of the other BS it is supposed to do.
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Old 06-28-2012, 05:10 PM
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Re: First gear mystery

I think this is exactly what's happening. Obviously the car can be stopped with the engine still running, so disengagement or slippage of some type is necessary. As the car speeds up, eventually the engine and transmission speeds roughly match and can be "locked" together. I imagine what I've noticed is that point when this occurs and it feels like a gear change when I have first gear selected. Tks to Savvas and others.
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Old 06-28-2012, 05:30 PM
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Re: First gear mystery

Here's a good video about how a torque converter works (warning - heavy metal music).

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Old 06-28-2012, 07:51 PM
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Re: First gear mystery

Interesting video. Thanks Dan S.
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