Bionic Man wrote:
Repeating myself, but I find it hard to believe that when EVERY modern vehicle I drive runs 200* normal operating and that is deemed as too hot. I can buy that with the older fluids but with the new synthetics I’m just not convinced.
But that is just it. Just because the sump is reading 200F(which is abnormally high unloaded in all the 68RFE trucks I have driven in the Texas heat) does not mean that it is 200F in hotter parts of the transmission. You may be reading 200F at the sump, but it may be 250-270F at the line going to the cooler. You can check it with a laser temp gun the if you have one.
Also, I do remember seeing
this thread over at the Cummins forum where I guys said that his temp unloaded in a 68RFE was 190F and Transengineer stated that that was about 20F higher than normal for unloaded. He also stated that it might be getting that hot due to the thermal bypass valve being stuck.
So if you are seeing 200F unloaded in a cold state like Colorado, I would definitely check that valve. It may be fine when unloaded, but could cause the cooling system to have to work over time to keep it in check when loaded.
