I am starting to think I may need to have the c6 in my E250 rebuilt. The previous owner had used the van to pull his travel trailer. He said he over heated the trans once. He had it checked out and added a cooler. Trans checked out okay and never overheated after adding the cooler. After having the van for a bit I added a trans temp gauge in the port next to the kick down bar on the drivers side. It always seemed to run on the warm side. It would get up to about 185* if the outside temp was in the 90's and I had the CC set for 65mph. Just here recently I noticed that it would shudder a little shifting from 2nd to 3rd under constant light throttle...like it couldn't decide if it wanted to shift or not. If I let off it shifted immediately and if I gave it a little more throttle the RPM's would come up and it would shift fine. I figured I would flush the trans and add a larger cooler that I had purchased (from a 6.0l). I replaced the filter and flushed the trans. I went ahead and just bypassed the auxiliary cooler so I could still drive it while I mounted the larger aux cooler I purchased....so it is just running through the stock radiator one. After the flush it is back to shifting perfect agian, but it is heating up very quickly and getting hot.....between 200* and 215*. Any idea what could be causing it to heat up? It doesn't appear to be slipping. Is there anything else I can check?

I do think my gauges may read a little hot. The water gauge goes up to about 207* and then the thermostat opens....though the thermostat opening is supposed to be 192*.

 

Synthetic and a cooler. C6s run warm anyway. Especially if they have a higher converter in them.