evil_goat

When Cruising at 55mph, my rpm is 1750. I confirmed that this is normal with an online calculator. When I let off the gas, the rpm drops quickly to 1250 and I am even still traveling at the same speed. This also happens at lower speeds too, and the rpm goes down to 1000. Is this normal? If it is, then why does it happen? Is the torque converter what causes it? Also my transmission is the AW4.

jpz

Are you asking if it is normal for your RPM to decrease when you take your foot off the gas pedal? I'm confused by your question.

If that is your question, then yes that is normal for an Automatic transmission.

evil_goat

Yes, assuming that the speed remains the same.

Spencer_P

Yes.

jpz

I'm still not fully understanding what you are asking.

I'm wondering if this is your first vehicle with an automatic transmission. If it is, then that may explain some of my confusion.

When you let off the gas, your speed will slowly drop because you are no longer providing power to the drivetrain. In a stick shift, you will tend to see the RPM immediately remain the same or slowly drop as speed drops (assuming you still have the clutch engaged).

In an automatic transmission you will see a more rapid drop in RPM as well as speed slowly drop because at that point the transmission disengages the lock up (assuming it was locked) and you have no mechanical connection between the engine and transmission.

If that is not what you are asking, then my only answer left is Colonel Mustard used the knife in the kitchen.

evil_goat

You have given a good answer. This is my first vehicle with an automatic transmission because it is my first vehicle ever. So based on your answer, stick shift cars are more effective at engine braking?

jpz

Yep, a stick would do better with engine braking because the engine and transmission are mechanically connected (again, assuming you keep the clutch engaged).

boxburn

Put it in 1-2 and you'll feel the engine braking pretty well, although it doesn't change gear into 2nd until around 40mph. 3 also gives engine braking when it is in 3rd. D provides no engine braking. A manual will always provide better engine braking as the engine (with clutch engaged) is in a direct mechanical connection to the wheels, whereas an auto has a fluid coupling (torque converter) in the middle which allows slip. It wouldn't surprise me if some or most modern autos can give pretty good engine braking in any gear though.

doublechaz

Being your first I'll also put it out there that if you use the gear selector to manually select a lower gear to achieve engine braking, don't shift down too far at speed and over rev the engine. You probably knew, but just in case...

My 2009 Chrysler 300 has pretty much zero engine braking in the normal D drive selection. It has very minimal engine braking when manually selecting 3. The only other selection is 1 (yes it skips the option of 2 becuase it seems Chrysler engineers are jerks) and that has huge engine braking, but can only be selected from about 23mph or slower.

evil_goat

Sometimes I need to put it in gear two for engine braking when I am going down a winding road at 30-40 mph. Since it is in the 1-2 selection, do I have to be afraid of it going into gear 1 when I don't want it to?

IJM

If you have the selector in 1-2 and are in 2nd gear coasting downhill, the transmission will downshift when you get below a certain speed (depends on tire diameter and gearing). There's no need to worry about overrevving the engine, but it could cause some oversteer if it happens while you're turning on loose or slippery surfaces.