Bilybobjef

As of late I've noticed that my transmission (5AT) has been acting a little wierd I think. When I'm cruising on the highway at like 70 lets say and completely let off the gas to coast, the engine stays at the RPM's it was at when I was on the gas at 70 instead of dropping to 1000 something like I thought it used to. It sounds like my engine is winding down and the car slows down quicker than it used to. I'm going to call the dealership tomorrow to schedule something but just wanted to know if anyone else experiences this or am I wrong and its supposed to hang at the same RPM whether or not I'm on the gas. I'm pretty sure not because at lower speeds it doesn't. Thanks for the help everyone.

dom

You said,

And then

If its staying at the same RPM then it should'nt be slowing at all I think? Or did I misunderstand what you were saying?

Bilybobjef

I'm sorry I meant it stays at the same rpm that it was at when I was on the gas maintaining speed but then slows down what feels like faster than it used to and the rpm's drop gradually as the speed drops. My concern is that it doesn't drop the RPM's to a coasting 1000 something instead it only drops as the car slows. Its tough to explain and understand I think, sorry about that

sauceman

There's absolutely nothing wrong there. If it dropped immediately to 1000rpms, then you should be concerned, because it isn't supposed to.

With higher rpms, there's higher oil pressure in the torque converter, which makes your tranny move. Since you are already moving, and at high enough rpms, the torque converter drives your engine, much in that way a standard transmition would.

Viking

Bilybobjef did you used to own a Manual Transmission?

cheepung

that was my concern as well. i used to drive 5 speed and i just does not like the AT on TSX. The car just keep going unless you apply some brake. If i let go the gas on my 5 speed, the car will slow down right away. I used this method if i need to slow down my car without applying any brake to save fuel and brake pad. The TSX just keep going even you let go the gas.

Chee

Bilybobjef

Yes I did own 5speed but something felt different. Thats why I asked because I can never remember if it used to do it or not. I did notice that at like 20-40 it will drop the rpm's and coast but above it wont. Thanks for the help all, guess I can cancel that appointment

dom

My AT slows down on its own just fine.

iamhomin

Okay I'm really confused. But from my understandings (if I'm comprehending your post correctly), the RPM's are supposed to drop when you coast without gassing.

I don't think there's anything wrong with your car..

slo007

That's how automatic transmissions work. The RPM stays high at high speeds because there's no more gears for it to shift up to.

The RPM goes down at low speeds because the transmission shifts up to save fuel. If you go into SS mode, you'll see the car is in 4th or 5th gear at barely 40 mph (no acceleration). When you accelerate, the transmission will down shift to the desired gear and the RPMs will go up again accordingly.

Viva 5AT!

drchaos

There is also the issue of torque converter lockup. It usually happens in higher gears (3-4-5).

In "regular" use like starting from a stop the torque converter does not mechanically couple
engine to transmission, it happens only by a turbine turning fluid which turns another turbine. There
can be some slippage and torque multiplication. At higher speeds and if acceleration is not strong
the transmission computer will tell the torque convert to lock-up, meaning to activate a direct
mechanical linkage. This will feel a bit like half an upshift in slow motion. RPMS will go down a bit and for a little
while RPM and car speed will be proportional just like in a manual. But if you either brake more
or step on the gas more it will unlock and the ratio between engine and transmission will vary
once again depending on load etc.


So it's not just 5 gears but 5 gears either with or without TC lockup.

Bilybobjef

That sounds a bit like what is happening. I have an appointment on the 20th and will definitely bring that up to the tech on the drive. Thanks for the additional information.

slo007

Now can someone explain what over drive means in terms of our 5AT TSX? How does it work?

drchaos

Nowadays overdrive doesn't have much of a mechanical meaning other than the fact that
in the highest "overdrive" gears, the input to the transmission will be turning slower than
the output.

On traditional manual transmissions back in olden days, in the higest gear, there was a
1 : 1 ratio between the engine RPM and the RPM of the driveshaft. There was of course
another gear ratio in the differential.


In my message about the torque converter lockup---that is a completely normal
and designed in feature of the transmission. It gives you more efficiency, closer
to a manual.