Prepare The A340F Transmission In Your Tundra For A Little Off Road Fun

Posted by on Monday, January 13th, 2014

The A340F is a four-speed automatic transmission designed and built by Toyota. It comes from a family of transmissions that include the A340H, A340E, A341E, A343F and A350E. The A340F was first put into production in 1985 and was eventually taken out of production at the conclusion of the 2004 model year.  It was used exclusively in four wheel drive trucks. It could be found in the 4Runner, the 4-Pickup, the T-100, the Tacoma and the Sequoia. It could also be found in the very popular Tundra full sized pickup.

Toyota Tundra

Toyota Tundra image from

The Tundra is a very capable truck and a large, dedicated group of owners have used many off them for a little off road fun, while still maintaining them for daily use. Unknown by many of these owners, taking a vehicle off road can be very hard on an automatic transmission. Let’s take a look at a couple of things you can do to prepare the A340F transmission in your Toyota Tundra to better handle the stresses of off road use.

The biggest problem you are going to run into when using your Tundra off road is the generation of excessive heat.  Overheating is the number one destroyer of all automatic transmissions, regardless of make or model, and the A340F transmission is no exception.

Ideally you want to keep the temperature of your transmission under 200 degrees. For every 20 degrees you go beyond this limit, you severely risk cutting the life span of your transmission by a factor of two. To better understand this concept, let’s take a look at what happens to your transmission as it reaches 260 degrees, which is not hard to do, nor is it uncommon. At that temperature, the life span is reduced to 1/8th what is considered normal.

Toyota a340f

Toyota a340f image by

In addition, at temperatures as low as 240 degrees, the organic oil based transmission fluid can start to turn to varnish. Once this occurs, you are almost guaranteed a complete failure of your A340F transmission. The best way to ward off overheating is to install an aftermarket transmission cooler. You should search for the biggest transmission cooler that will fit your Tundra. For the most efficient operation, mount the cooler in the transmission line coming out of the factory cooler. Also be sure to mount the cooler in a location that will see adequate air flow when the vehicle is in motion.

Another good idea is to swap out your organic transmission fluid for a synthetic transmission fluid. Synthetic fluids have much better properties under extreme temperatures (both hot and cold) and will not break down nearly as easily as their organic cousins.

Eventually, due to high mileage or abuse, you will be faced with a decision to replace the A340F transmission in your Toyota Tundra. I highly recommend going with a re-manufactured transmission over one that was simply rebuilt. A re-manufactured transmission comes with a much better warranty; three years compared to an average 90 days for a rebuilt transmission. 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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