Don’t Let Excessive Heat Destroy The 4L80E Transmission In Your Hummer H1

Posted by on Tuesday, July 22nd, 2014

The 4L80E is a four speed automatic overdrive transmission developed and produced by General Motors.  It is the predecessor to the TH400 three speed transmission, and in fact shares some component in common with this transmission. The 4L80E comes from a family of transmission that includes the 4L85E, a slightly heavier duty version of the 4L80E. The 4L80E is a heavy duty transmission capable of handling up to 440 lb-ft of torque.  It comes with a fairly steep first gear ratio of 2.48:1 and a final overdrive gear ratio of 0.75:1 (25% overdriven). This transmission was first introduced to the lineup in 1991 and was available as recently as 2013. The 4L80E automatic transmission could be found in a variety of vehicles, including the Chevrolet Silverado 2500HD / 3500HD, the Sierra 2500HD / 3500HD, the Avalanche ¾ ton, the Rolls Royce Silver Spur, the Bentley Turbo R, The Jaguar XJR and the Aston Martin DB7. It could also be found in the Hummer H1.


The Hummer H1 is an extreme heavy duty sport utility vehicle. It was originally designed solely for US military use. Eventually, Hummer was acquired by General Motors and a civilian version of the vehicle was created. It was built between 1991 and 2006, when the high cost of gas finally forced GM to stop producing it. The H1 had an incredible 16 inches of ground clearance, and could handle slopes with up to a 60 percent grade. It could also makes it’s way through water as deep as 30 inches. It was available only with 4 wheel drive, and could be ordered as a pure SUV or as a pickup truck with a tiny pickup bed.

The H1 is a status symbol of the rich, and can be found used for everything from hauling golf clubs to hauling heavy trailers. Hauling heavy loads can really take a toll on the 4L80E transmission.  Towing is usually the number one cause of automatic transmissions overheating, and overheating is the number one killer of all automatic transmissions, regardless of the make or model. Ideally, your transmission should not get warmer than 200 degrees. For every 20 degrees you go beyond this recommend maximum limit, you risk cutting the life span of the transmission by a factory of two.  Therefore, it is critical that you take steps to stop the 4L80E transmission in your Hummer H1 from overheating.

Start off by installing an aftermarket transmission cooler to supplement the factory transmission cooler.  The larger the physical size of the cooler, the better it will cool, therefore it is recommended that you purchase the largest cooler that will fit the front of your Hummer H1. Look for a cooler that is made of a stacked plate design. These types of cooler are much more efficient and durable than the more commonly found fin and tube designs.

Next, install a deep sump aluminum transmission oil pan. Most deep sump transmission pans will add 3 – 4 quarts of fluid capacity to your 4L80E transmission.  This extra fluid will help keep your transmission running cooler.  Aluminum is much better at dissipating heat than the thin sheet metal that the stock transmission pan in made of. This will also help remove unwanted heat from your transmission. When shopping for a transmission pan, look for one that has built in cooling fans.

Sooner or later, due to high mileage or abuse, you will be faced with a decision to replace 4L80E transmission in your Hummer H1.  I highly recommend doing so with a re-manufactured transmission over one that was simply rebuilt. A re-manufactured transmission will include major internal modifications and upgrades designed to make it both stronger and more durable. A rebuilt transmission will not include this feature. A re-manufactured transmission also comes with a much better warranty; three years compared to an average 90 days for a rebuilt transmission. And in the rare event that you need to contact the company that re-manufactures transmissions, they are just a quick phone call or email away!


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