Mechanics

TRANSMISSION DOES NOT SHIFT INTO LAST GE

1998 Dodge Avenger

Transmission problem
1998 Dodge Avenger 6 cyl Front Wheel Drive Automatic 130000 miles

My transmission does not slip into the last gear until the car has warmed up. Was the car made to do this, or is the transmission bad? If I can remember correctly, I think the car shifted fine in the summer. The car shifts all gears good besides this problem that I have been having. After about five minutes of driving, the car finally shifts into last gear, and continues to do so until parked for a while. If it is a bad transmission, is there anything I could do to improve my transmission performance besides replacing the transmission itself?
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Hunter132
January 17, 2010.




Some automatic transmissions will not shift into overdrive when they are cold because engine rpm will be too low for the transmission's front pump to move the thickened fluid through the cooler.

More commonly, you are likely feeling the torque converter lock up. It feels like it is shifting to a higher gear, but to prove this is what you're feeling, hold the gas pedal steady, then lightly tap the brake pedal. That is the signal for the converter to unlock. You will hear engine speed pick up and will see it on the tach, then rpm will go back down in two or three seconds. In the summer, it is common for lockup to occur within one or two miles of starting a cold engine. In the winter, my Caravan doesn't go into lockup for about seven miles.

When you start out, you should easily feel three definite upshifts since you have a four-speed transmission. If you only feel two upshifts, application of overdrive is likely being delayed because of cold temperatures. When transmission fluid is cold, it is too thick to flow freely to provide proper lubrication. Keeping engine rpm up helps the pump to move this thick fluid.

Caradiodoc

Caradiodoc
Jan 18, 2010.
So this is normal? I do feel the first three upshifts, but the fourth doesn't come until I'm well away from home. (Does not go into overdrive) Will changing my transmission fluid help? -Thanks for your response.

Tiny
Hunter132
Jan 18, 2010.
Leave it alone; everything's working properly.

It's going into overdrive when you feel the third shift. One shift puts it from first to second gear; the second shift puts it in third gear; the third shift you feel is putting it into overdrive, (fourth gear).

That fourth " shift" isn't a gear change shift. It's the torque converter physically locking up. The torque converter is two fans facing each other in an enclosed bagel. One fan spins transmission fluid, and the fluid spins the second fan. The lack of a solid mechanical connection between the two fans is what allows the engine to stay running when the car is stopped but in gear.

The second fan will never turn as fast as the first one, and that is a source of loss in gas mileage. To overcome that, Chrysler was the first company to incorporate a lockup mechanism in 1977 to increase fuel mileage. It simply joins the two fans mechanically after the engine is warmed up, the transmission is in third or fourth gears, and vehicle speed is above 35 mph. It will unlock when you tap the brake pedal or completely release the gas pedal in preparation for coming to a stop.

Caradiodoc
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Caradiodoc
Jan 19, 2010.
Thanks for your post. I know little about cars and I get a little nervous when things don't work out perfect.

Tiny
Hunter132
Jan 19, 2010.

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