The Popular AW4 Automatic Transmission And Common Problems Associated With It

Posted by 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.

The AW4 transmission used in many Jeeps


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.

Internal view of the AW4 transmission


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.

Investing in a good transmission cooler is important


If your customer’s AW4 has made it last shift, I strongly recommend you replace it with a re-manufactured transmission over one that has been simply rebuilt. I made this recommendation for two good reasons. First, the re-manufactured transmission is going to include upgrades and modifications designed to make them last longer. A rebuilt transmission will not. Second, a re-manufactured transmission will include a much better warranty. Usually three years compared to an average 90 days for a rebuilt transmission. And get this – if the re-manufactured transmission fails within the warranty period that will also cover your R&R cost to replace your customers transmissions.  That could save your shop a lot of money in the long run.


2 Responses to “The Popular AW4 Automatic Transmission And Common Problems Associated With It”

  1. owen palmer says:

    My tranny has worked fine for 267,000 miles , I regularly change fluid and filter and than I cracked the bell housing and pump seal started leaking ..every time I checked fluid it was always over full mark whether engine off or at idle , in neutral .
    I have replaced bell housing (new) and pump seal with old torque converter reinstalled …still I can not get a proper fluid reading at idle , in neutral , it shows way over max. With 4 QTS. Fluid added ????
    Sincerely owen palmer

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