I have this same problem especially in the summer months. I am a mechanic and when i went to a class for a certification through work I asked the instructor. He wasnt too familiar with the issue and mentioned it being electrical or the sensor as possibilities but youre exactly right when the sensor tells the computer the fluid is hot and it trips your trans temp light the light being on is why you arent shifting properly, that would be the transmission telling the computer it needs to cool down and the computer may have it skip gears or turn off the overdrive, things like that. which explains why it drives fine when the light is off. I did a trans fluid exchange and still had the same problem even after. I have yet to figure out what it is but my guess may be something with the sensor or just overheating from use in which case adding a trans cooler may not be a bad idea! the trans fluid echange itself wont solve the problem thats more of preventive maintenance but since we already have a problem it will continue no matter how many times we change the fluid. that being said oil breaks down and gets contaminates and older used oil/transfluid that has broken down can be easier to heat up so the exchange may help but wont solve the issue. hopefully I wrote that in a semi coherent way... if not i did type it at 4 am lol

 

I'm wondering if the temp sensor can be pulled and bench tested?
Any one have specs for that unit?
Then again, maybe the harness connector is dirty and/or corroded and a good cleaning of the contacts might help?

 

for the price they quoted for 375, is that a transaxle service? I have had mine done several time do to my extreme driving every 40000 miles or so and that's what I pay, they flush tranny, new filters and fluid, change out transaxle fluid, and frt and rear diffs

 

Is there a permanent ATF gasket available for the Dakotas ?

 

Don't know what you mean. ATF is a liquid and a gasket is a solid.

Do you mean the transmission pan gasket? Most of the parts store sell a filter kit which includes the gasket. The gasket isn't rated as "permanent", it's usually replaced each time the pan is R & Rd.
HTH

 

Both my K2500 Chevy Suburban and my Wife's 2000 Mustang have what I term a permanent (or reusable) transmission pan gaskets which came as OE. They are thicker than the crap cork gaskets, and have metal grommets around the bolt holes so they cannot be over compressed. Much cleaner and more efficient than cork, or silicone gasket seal. Just wondered if Dodge/Ram had caught up yet.

 

I'm having the same problem and have had a few qualified persons recommend the bench test but have not had a chance to research what the specifications are, not even what a new one will cost. I might get to it by end January so will advise if I get there.

 

just do your Red Green imitation and put duct tape over it. ok ill be serious now. i think most have the fluid in at the rear left side. here is an EXTERANL filter, i found. have one on my 01 dak. my idea is when you put a new filter in side this one will help from having to do the inside one as often.*
the old auto zone 2210 magenfine filter is no longer available at auto zone. BUT i did find the same thing as JX-160 brand-- ATP. at a real parts house uses 3/8" tube. a JX-150 for 5/16 tube. ONLY use high pressure hose. If you must. SAE J1019 217 psi working. NOT fuel hose for a carb engine.