I have a New 2005 Dodge Dakota SLT 4.7 V8 w/ Automatic Transmition. I have noticed that in cold weather, the last few days have been 6 degrees in the morning, that the RPMs are higher than they normally are. On the highway I am doing 75 at 2000rpms, but in the cold it seems to bounce back and forth between 2300 and 2800 but it does not feel like it is shifting. After I have driven the truck for a half hour to 45 minutes it seems to work fine. I have never owned an Automatic. Is this Normal?

 

That's normal with automatics. The torque converter is a fluid coupling rather than a mechanically locked device like the clutch in the manual transmission vehicles you've driven. It's basically a hydraulic pump and a hydraulic motor coupled closely together, instead of the spring-loaded plates with friction elements you're familiar with. The extra slippage in the torque converter means the engine turns faster, helping to warm it up. The lost energy in the converter is converted directly into heat in the transmission fluid too. There is a clutch inside the torque converter which engages when the powertrain is warmed up in order to give better fuel economy and drivetrain efficiency, which is why your RPMs are lowest when your truck is warmed up. Some of the RPM variation could also be from the closeness of 4th and 5th gear (.75 and .69 IIRC). That shift is very hard to detect. My truck goes from direct-ratio 3rd to 4th to 5th in about a second under light acceleration.

 

Thank you ptschett. That makes sence. When I talked to the Dodge Service Manager (before I came to this site) He had never heard of this happening. I guess that is why he is the manager and not actualy working on the car.

 

PT, have you had a chance to do any towing yet? I have an 05 QC V8 Auto with tow package. When hauling 2 place open snowmobile trailer with 2 sleds down the highway, the trans won't come out of 3rd gear (with and w/o tow/hual mode on). This is with cruise on. If I hit the cancel and resume button it would shift into 5th and run there for several miles then shift back to 3rd.