I have a 02 3500 with an auto, and it has a built in transmission temp warning light. Does any one know at what temp he transmission is when this light is activated? I'm wondering if I should put in a transmission temp gauge or does the light come on at a low enough temp to prevent damage.

If the light comes one of two things, either the sending unit is defective or your tranny has exceeded 255-260 degs at which things begin to fry in your tranny. In April when my tranny temp light came on it was too late to save my tranny. Coolers were plugged and didn't flush so required replacement and with remanufactured tranny bill came to $3800. :'(<br><br>No one should go without tranny temp gauge. Install sending unit in-line just before fluid enters cooler. This will give you warning in time to take remedial action before tranny goes. <br><br>Smell your fluid on dipstick if it smells burnt, some damage may have already been done, change fluid immediately. ???

Thanks for the info, it sounds like the trans temp light is just as useful as a oil pressure light. By the time it's on, it's too late. I would think anything over about 210 deg would cause damage.

I asked the dealer about this when I was having tranny woes, and they said the light will come on around 220-230. Definitely get a gauge!<br><br>Mike

Damage starts around 255 degs., seals begin to fry and become brittle. Plastics distort and become pliable. Standard non-synthetic fluid rapidly loose lubricating abilities. <br><br>The tech who replaced my tranny said that temp light should come on at 255degs Pulling a 15% grade for one mile my tranny temp light did not come on when temp was at 240 degs. It sure came on when the tranny went. Engine temp was still under 200 degs. <br><br>