The Popular AW4 Automatic Transmission And Common Problems Associated With It
Posted by Regis F. on Tuesday, May 28th, 2013
The AW4 automatic transmission was designed jointly by AMC and Jeep. It was actually produced by Aisin-Warner. It has four forward speeds and shares many common parts with Aisin- Warner’s 450-43LE transmission. It first went into production in 1987 and lasted until the end of the 2001 model year. It was used in many popular Jeep vehicles, including the Jeep Cherokee and Jeep Comanche. One thing to note when swapping out the AW4 transmission is that it came with two different input splines; early units used a 21 spline shaft and later ones used a 23 spline shaft. Customers that own Jeeps seem to keep them forever, so you are likely to see one roll through your shop every now and then. Here are a couple of common problems associated with the AW4 transmission.
Problems associated with the transmission throttle valve cable: If your transmission starts to act funny, like it sometimes is slipping and yet other times going into gear very hard, try checking the adjustment of the transmission throttle valve cable. They are relatively easy to check and easy to adjust, but there are different methods for different year vehicles. Refer to the shop manual for the proper adjusting instructions for your vehicle.
Problems associated with one of the solenoids: This transmission has a number of different solenoids. The solenoids are used to control certain functions within the transmission electronically, such as moving a valve in the valve body. The main component in the solenoid is a coil of wire that when energized, creates a magnetic field. It is this coil of wire that will give you the most problems. It is not uncommon, especially in high mileage vehicles, to have this wire either break or internally short out. The quickest and easiest way to check a solenoid is to use an ohm meter. A properly working solenoid will usually return a reading of 20 – 30 ohms. Any reading outside this range may indicate a bad sensor.
Problems associated with over heating: This transmission is notorious for overheating. It was originally designed to operate at a maximum temperature of around 200 degrees. Here is a good fact to know; for every 20 degrees you go above 200 you cut the life of the transmission by a factor of two. At that rate it won’t take long to fry the transmission.
I would do a couple of things to control the heat. First, install the largest cooler that will fit the vehicle. Next, talk the customer into investing in a deep sump aluminum pan. Make sure the pan is aluminum and not steel (aluminum dissipates heat better). Finally, convince them to convert over to synthetic fluid. Synthetic fluids behave much better under higher temperatures than conventional fluids do.