Understanding the Components of the Transmission Valve Body

Posted by on Monday, March 31st, 2014

A typical transmission valve body

Example of a transmission valve body.
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The transmission valve body is made up of three major components:

  • The upper valve body.
  • The lower valve body.
  • The manual valve body.

The transmission’s valves manage fluid direction and pressure. They accomplish this through hydraulic circuits that connect to the main transmission housing. The valves receive oil from the governor, which varies fluid pressure in accordance with vehicle speed.

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Transmission Components: Examining the One Way Clutch

Posted by on Friday, March 28th, 2014

Typical sprag clutch

A typical sprag clutch.
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A one way clutch, also known as a “sprag clutch,” is a type of freewheeling clutch that helps transmissions to transfer torque and shift smoothly between speeds. When this component starts to go bad, problems can range from annoying clicking sounds to complete transmission failure.

A one way clutch can be identified by its resemblance to a roller bearing, but instead uses stationary sprag bearings shaped like the number “8.” The clutch rotates easily in one direction, but binds the moment direction is reversed. Built-in springs soften the clutch’s reaction to the change, keeping the driver from feeling a backlash.

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Diagnosing Torque Converter Problems: Procedures for All Vehicles

Posted by on Thursday, March 27th, 2014

torque converter diagram

Diagram of a typical torque converter.
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Torque converter problems can be the most challenging of all automotive repair issues to diagnose. Fortunately, there are a number of signs to look for, and a few basic tests that will reveal if a faulty torque converter is at the heart of the vehicle’s problems.

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The A413 Transmission: Three Speeds Never Felt so Good

Posted by on Wednesday, March 26th, 2014

A413 transmission

A413 transmission.
Image source: EBay

The A413 transmission is one of the more common gearboxes you’re likely to see if you work on Chrysler vehicles. While lacking the bells-and-whistles of newer units, it’s a solid performer within the limits imposed by its three speeds.

The A413 is part of Mopar’s legendary series of Torqueflite transmissions, which dominated Chrysler vehicles from 1956 up into the 2000s. Like all gearboxes in that series, it has a reputation for reliability and ease of use. One of the key limitations of its design is that it was created to work with six and eight cylinder engines. This fact becomes problematic with today’s higher-revving four- and five-cylinder motors. Nonetheless, the Torqueflite transmission series is like the original Volkswagen Beetle: its sheer popularity ensures that you will be seeing it on the road and in your shop for many years to come.

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Troubleshooting for the Ford 4F27E Transmission: A Step Forward for Electronic Gearboxes

Posted by on Tuesday, March 25th, 2014

Ford 4F27E

Ford 4F27E.
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In recent posts we’ve looked at the rough transition the auto industry has had from classic hydraulically controlled transmissions to electronically managed units. While some of the early electronic efforts were less than spectacular, car makers sometimes actually learn from their mistakes. Case in point: the Ford 4F27E transmission, which represents solid gains over earlier versions.

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PCM Reprogramming: A Step-by-Step Guide for Transmission Technicians

Posted by on Monday, March 24th, 2014

PCM reprogramming

Technician reprogramming a PCM.
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Please note: in this article we will be using the term “PCM” to refer to the electronic control module (ECM) unit that controls the transmission. On most vehicles, PCM refers both to this component and to the engine control module (ECM). Chrysler, however, still refers to the transmission control module (TCM) separately from the engine module, and so do some technicians.

Now that we’ve covered the basics of transmission PCMs, let’s talk about reprogramming. PCM reprogramming is one of those skills that some old-school transmission technicians approach hesitantly. Many of us old-timers grew up in an era in which auto repair was done with a few hand tools and a lot of elbow grease, along with a good ear for what was going on under the hood. Any mention of a programmable “whatchamacallit” just doesn’t sound right to us.

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Understanding the Transmission PCM: Your Automobile’s Personal Computer

Posted by on Friday, March 21st, 2014

PCM diagram

Diagram showing how the PCM functions as part of a car’s electronic systems.
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Understanding the components of a modern transmission is one of the factors that separates run-of-the-mill technicians from great ones. Take the transmission PCM, for example. We all know that it’s the brains of the operations. But how does it do the thinking? Let’s take a peek inside the typical PCM and see if we can find out.

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Tips for Automatic Transmission Troubleshooting: Mastering Ohm’s Law

Posted by on Thursday, March 20th, 2014

Diagram of Ohm's Law

A diagram showing the basics of Ohm’s law.
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As computerized components become more integrated with automotive systems, the need to understand how these units work will become ever greater. This is certainly true when it comes to automatic transmission troubleshootingFortunately, most electronic issues come down to basic malfunctions which can be diagnosed relatively quickly, especially if the technician has a good understanding of fundamentals like Ohm’s law.

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The Chrysler A-604 Ultradrive Transmission Series: Too Much, Too Soon

Posted by on Wednesday, March 19th, 2014

Ultradrive transmission

The Ultradrive A-604 transmission.
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The A-604 Ultradrive transmission series was a classic example of “too much, too soon.” Introduced in 1989, it was the first transmission to use adaptive shifting and other capabilities that were considered remarkable for the time. The problem was the 1980s technology that went into the A-604; it simply wasn’t up to the job. From a business perspective, this boondoggle may have been a case of poor inter-departmental communication. From a technical point of view, it was simply a mess.

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How to Check Transmission Fluid: Technological Changes Lead to New Maintenance Rules

Posted by on Tuesday, March 18th, 2014

Transmission fluid level

The results of a transmission level check.
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Good automotive maintenance comes back to knowing the basics. But those basics never remain the same for very long, thanks to ever-advancing technology. Take checking transmission fluid as an example: this was once a fairly simple task.  First, check the level. Then smell the fluid; a burnt odor, commonly known to as “pink stink,” was the most common warning sign. Lastly, look at the color on the stick. Anything other than a bright cherry hue was cause for concern.

Those are the basics that every shade tree mechanic from coast to coast knows. But today’s professional needs to be aware of changes that have happened over the last few years that have rewritten the rules about how to check transmission fluid. Let’s start with a look at how the fluid itself has changed.

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