Automatic Transmissions


The general consensus seems to be that automatic transmissions are better for plowing snow, for many reasons. I will not go into them here. What I’d like to talk about is how to keep them operable, while using them to plow snow, and tow. Since I plow with an auto myself, and burned one up (in a sense), I’d like to help you NOT burn yours up with some suggestions. When I had my GM TH350 rebuilt two years ago, it cost me about $1,000. Most automatic transmissions work the same way, and most of the principles are the same. I am going to generalize in my recommendations. Some of your trucks may already have some of the features I’m going to talk about, and some of you should add these features. Some of you may also know the tips I’m about to recommend too.


The worst enemy of an automatic transmission is HEAT. It’s common for transmission fluid temperatures to exceed 350 degrees. A “normal” operating temperature would be approximately 200 degrees. I’ve actually seen a transmission that caught fire due to overheating! Anything you can do to help your trans run cooler will extend its life. One simple thing you can do, is not shut your truck off after heating up the trans. One way of heating up the trans rapidly would be pulling a trailer up a long steep hill. Shutting the truck off when you get to the top to say, “mow a lawn” would be a bad thing, the same as towing a boat up a long boat ramp, then parking the truck in a parking lot at the top, and shutting it off. Plowing a driveway, and shutting the truck off to shovel the walks is a bad practice to get into. The same as plowing a parking lot, and shutting the truck off while you go grab a cup of coffee is not a good idea. When you shut the truck off, the trans fluid stops circulating through the cooler. Letting the truck idle for say 10 minutes, or more, or maybe even less (depending on the vehicle) will help bring the transmission fluid temperature down. This is also why it’s a good idea to keep a full or near full tank of fuel. Many of us never shut our trucks off when plowing, myself being one of them. In addition to plowing, just running your truck in 4wd generates more heat than normal. Add to it driving in 6” of snow or more, and that’s even more of a strain, which generates more heat. Especially heavy wet snow, it gives more resistance to your tires, which makes the trans run hotter. The extra weight of the blade on the truck, and ballast in the back adds to it all too.


There are a few things to keep in mind about automatic transmissions. When you drain the fluid in the pan only, you are only draining a small percentage of the total amount of fluid in the transmission. For example: The GM TH350 transmission holds approximately 21.5 pints (about 11 quarts) of fluid. Draining the fluid in the pan only removes about 8 pints (4 quarts). This means that inside the transmission and torque converter, there is still 7 quarts of fluid. So in this case, you’d be changing less than half of the fluid. For the half hour or less it takes to drain and add 4 quarts, it’s worth it. Compare the cost of time and fluid to having your transmission rebuilt, and you’ll see the savings potential. You could drain the four quarts, run the truck for a day, and drain the pan again, adding another 4 quarts. This will replace much of the fluid with fresh fluid. It will be “diluted” fresh fluid, but it’s still cheap insurance against having your transmission rebuilt. Fluid should be drained when the transmission is hot, never “first thing in the morning”. The main reason most trans pans don’t have a drain plug, is because if they did, many people would just drain the four quarts, and think they just changed all the fluid in the transmission. It’s also because most people wouldn’t remove the fluid pan, and change the filter or filter screen as well as the fluid. It’s possible for you to drain the fluid in the torque converter yourself, but it’s a much more difficult job than just draining the fluid in the pan. Not only that, but if you want to go that far, you should have your transmission flushed at a reputable shop.


 What you can do


There are a few modifications you can make to help your transmission last longer, aside from letting your truck idle after putting a load on the transmission. 




















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