Don’t Let Your 4L80E Transmission Overheat. Discover The Importance of Keeping It Cool

Posted by on Thursday, October 25th, 2012

General Motors first started using the 4L80E 4 speed automatic transmission in 1991.  It was an option in heavy duty pickup trucks, vans and bare chassis’ (think motor homes) from General Motors brands Chevy and GMC. They could be found behind all sizes and kinds of different motors, including small blocks, big blocks and diesel engines. Since vehicles equipped with these transmissions were often designed as work vehicles and heavy duty vehicles, they are subject to heavy use and is some case abuse.



Heat is the number one cause of transmission damage. It is not a well-known fact, but these transmission are really designed to be keep under 200 degrees at all times in order to maximize the life of the transmission. For every 20 degrees the transmission gets over 200 degrees, it cuts the life expectancy by a factor of two.  Let’s put this in perspective. At 220 degrees the life of the transmission is cut in half. At 240 the life of the transmission is cut to a quarter. At 260 degrees the life of the transmission is cut to 1/8th.

Most owners have no idea what temperature their transmission is running at. Therefor the first item that should be recommended to your customer is a transmission temperature gauge. The transmission gauge sensor should be mounted into the transmission pan for the most accurate readings. The ideal time to install a temperature gauge is when the truck is having its transmission fluid replaced as part of its regular scheduled maintenance program. Aftermarket transmission temperature gauges are available from a number of companies including Autometer, B&M and TCI.

Transmission Temp Gauge


To prevent the transmission from reaching unacceptable high temperatures, the customer should be sold a deep transmission pan.  The ideal pan should be made of aluminum and include cooling fins.  The aluminum deep pan helps keep transmission temperatures in check by increasing the overall fluid capacity by 2 – 3 quarts of oil.  The properties of aluminum dissipate heat better that the stock steel pan and the cooling fins provide more air to surface contact to help speed up that process.

Finned Transmission Pan


An aftermarket transmission cooler is another add on that should be sold to the customer.  You want to mount the aftermarket cooler in line with the factory cooler and place it in between the factor cooler output line and the transmission input port.  The bigger the cooler the better your chances of keeping the transmission cool.  The cooler needs to be mounted in a place where it can pick up moving air as the vehicle is in motion. There are coolers available that have a built in fan equipped with on/off sensors. They are recommended for maximum cooling or to mount in positions where airflow in inadequate. Cooler are available from many companies including the companies mentioned above.

Rebuilding a 4L80 can be very expensive and you don’t need to spend your child’s college tuition to discover that fact.   I deep pan, cooler and gauge will probably set the customer back around $300 plus your installation time.  That is a bargain. This should be an easy sell and something that is recommended to all of your customers with heavy duty vehicles when they buy a new or re-manufactured transmission.

Sooner or later due to high mileage or abuse, you will be faced with a decision to replace your transmission. I highly recommend you replace it with a re-manufactured transmission over one that was simply rebuilt. A re-manufactured transmission will include major modifications and upgrades designed to make it both more durable and stronger. A rebuilt transmission will not. A re-manufactured transmission also comes with a much better warranty: three years compared to an average 90 days for a rebuilt unit. Let’s not forget to mention that after-sales customer service is top notch for companies that re-manufacture transmissions. They are a quick call or email away in the rare event you may need to contact them.

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