The Ally overheated and the temp hit 240 degrees for about 15 mins while running empty. Yesterday i changed the inner and outer filters and flushed out the cooler. I have done 4 flushes since i have owned this truck anyways I had the hose and jug setup to catch the oil. Started the truck and oil started pouring out of the transmission fitting for the return line. I checked to make sure i pulled the right oil line. I had to stuff a rag in the hole and hold it in there to complete the flush. To me it would appear that there is no oil circulation through the cooler if i have pressure on both lines. Any ideas what is happening and a possible solution. The old oil came out black and had a slight burnt smell.:(

mine did the same thing while flushing ,but have never had any temp issues with it as of yet,definitely was not expecting oil to come out of the trans though ,very messy:(

Depending on temperature, you're going to get some flow out of open port.

The oil makes a loop out through the coolers and back in. Be sure that your cooler's flowing freely and not plugged.

I blew out the cooler, transmission is running at 140 degrees now and shifts are firmer. Thanks for the replies.

I blew out the cooler, transmission is running at 140 degrees now and shifts are firmer. Thanks for the replies.

Glad to hear you got it straightened out. Don't know how many miles you have but heads up that it might come back again eventually.

The LU clutch paper on the '03 and earlier converters has been known to flake off at high mileage/number of cycles. This loose paper can obstruct the cooler and cause what you described. Allison switched from Aisin Seki to US made LU clutch material and then a US converter with the 6 speeds.