I had to replace the pan gasket because the new gasket would let all the fluid out on the floor and it still had the looped line for a cooler, and about 1/8' of sludge in the bottom of the pan. I installed a cooler for him but told him that I am not responsable if the tranny takes a dump on him. How to Install a GM Turbo 350 Automatic Transmission. Turn the integral nut at the tip of each oil cooler pipe in a counterclockwise direction with a flare-nut. Read the tech article on a TH200-4R Transmission Swap - Tech Article, brought to you by the experts at Chevy High Performance Magazine.

The GMT800 generation of General Motors’ fullsize trucks and SUVs is one of the most popular among truck enthusiasts—and for good reason. They’re thoroughly modern vehicles, but still relatively easy to work on, and were the first models to utilize the LS-type V-8 engines.

It was also the first generation of GM’s lovable oddball, the Avalanche. However, GM made some interesting choices with the standard configurations, some not always favorable to owners. One of which was the lack of a proper factory transmission cooler for Avalanche 1500 models. In online forums, there are plenty of horror stories about premature failure of the 4L60E transmission. Most are related to excessive heat or owners tuning their engines to produce more power than the factory transmissions were designed for.

Since we’re not planning on doing major engine upgrades that will push the trans beyond its limits, we decided to install a B&M SuperCooler transmission cooler to give us an extra measure of confidence when towing. We selected the model #70264, which has a 14,400 Btu rating. We found the cooler made a significant difference in terms of cooling and preventing heat soak.

Previously, we could get the transmission fluid to spike to 190 degrees or more with just a few wide-open-throttle runs, or on prolonged uphill grades. Afterward, we made repeated WOT runs and went up a steep, prolonged grade at full throttle, and the transmission fluid temperature remained steady at 150 to 160 degrees. A difference of 20 to 30 degrees can mean the difference between transmission failure or making it to your destination safe and sound when towing.

Follow along as we knock out this install in just a couple of hours.