So I literally just bought a 2005 dodge Dakota 4.7 automatic, it only has 87k miles on it so I figured for the price it would be a good rig for awhile. Seemed to run great and couldn't feel any problems with the trans soo I bought it.


few days later I was holding steady at 40mph and then I found the problem. It would go up and down in rpm (aprox 200rpm variance) and really vibrate bad when it did that. It was only around that 40 mph mark though never did it at slower speeds or interstate speeds.


I immediately took it to the transmission shop and he said bad news....your tran has milky (moisture) in the fluid. So not only is my radiator screwed up but my automatic trans also needs an overhaul.


Now I don't know wether to rebuild the one I have or buy a used one with a warranty. Can I just cap off the lines at the radiator and run an external cooler for the trans? My trans is the 545rfe correct?

 

Capping off the lines at the radiator and using an external cooler will make things easier. This way you don't have to swap the radiator right now. You do have the 545rfe trans. Might be cheaper if you can find one out of a junkyard then rebuilding. Always ask the tranny guy if he can find one to swap with and compare the price. In your case, there might be more wrong with it then what was found. Other components could have been weakened or rust could be starting due to the excess moisture.

Also check your coolant. If it was getting the water from there, your coolant will need to be replaced. Make sure to get as much as you can out, you don't want tranny fluid running through the engine block's water passages or block heater.

 

I would say Do the following,

Cap the transmission part of the radiator.

Run an external cooler.

Flush the coolant.

And just drop the transmission pan, change both filters, fill back up and do a fluid flush from the front lines by the new cooler.

Milky fluid does not mean the transmission is gone.

The engine rpm issue might be a sensor in the engine.