Why Gravity May Not Be Your Friend When Changing Your Automatic Transmission Oil


For an automatic transmission to work correctly over the long term, the lubricating fluid has to be in good condition. It's well-engineered by the manufacturers to cope with challenging conditions, but it will inevitably degrade as time goes by. As an owner, you can do your part by replacing the fluid at recommended intervals but must ensure that all of this lubricant is properly removed during a service visit. How can this be accomplished, and what can happen if you do not pursue these goals?

Trusting the Force of Gravity

The traditional way to remove old oil from an engine or a gearbox is simply to open the plug at the bottom of the sump pan and let gravity take over. This approach may be perfectly okay with the internal combustion engine, but it does not always work when it comes to an automatic transmission.

Getting around the Design

Problems arise due to the design of the transmission system. The lubricant has to be pressurised within the torque converter to enable the vehicle to change gears automatically, and as the converter is configured in such a way, some of that lubricant may become lodged within internal passageways. It may tend to stick to tiny particles of contamination (like microscopic metal shavings) and may not always flow through to the drainage area.

Drying in Place

The problem may be compounded when the vehicle is not in motion. As soon as the driver turns off the ignition switch, this will shut down the internal pump, and any lubricant already within the torque converter will stay in place. It may tend to adhere to the converter's outer surfaces, and some of it will dry in place, especially in high ambient temperatures.

Dealing with Stubborn Lubricant

However, good mechanics have a solution. They will attach a machine designed to pull the lubricant from the torque converter during a replacement cycle. This machine will also send a cleaning solution through to ensure that all of that contamination makes its way into the collection pan. Once this process has been completed, the mechanic can then introduce a fresh batch of lubricant to afford the proper levels of protection.

Handing the Job to the Professionals

So, if you think you can change the automatic transmission fluid yourself and do not need to bother a professional, perhaps you should think again. Make sure that you replace all of the fluid, not just some of it, so you can avoid future problems. 

For more information about automatic transmissions, contact a local mechanic. 


1 August 2022

Keeping Your Car in Good Condition

Cars are wonderful things. Unfortunately, they also have lots of technology and moving parts which can go wrong if they are not properly cared for. We hope that this blog will give you all of the info you need to service your car. We will be looking at subjects such as how to change the oil in an engine, how to replace a worn brake pad, and how to check the electrical systems on your vehicle. Everything you read on this page has been written by keen amateurs who have a really big passion for servicing their autos. We hope you love what you find here.