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Easy Transmission Fluid Change (Example: 1989 Chevy 3500)

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I write about maintaining and troubleshooting cars and other motor vehicles!


Why Change Transmission Fluid?

We don't often think about changing the fluid in the transmission like we do the oil, but they both should be changed periodically if you want your transmission to last a long time. Besides, changing the fluid provides the opportunity to check that everything is running as it should. Metal in the fluid reservoir can mean there is trouble brewing with your transmission!

Regardless of your driving habits, the parts in a transmission wear down. The transmission parts are always rubbing against one another just like the pistons in the engine.

Because of this friction, you need to change the fluid; not because the fluid itself has broken down, but because the metal parts in the transmission break down. Even though the transmission fluid helps reduce the friction between these moving parts, as well as cool them off, some friction remains, and this friction will cause micro-particles of metal to collect. There is a magnet in the fluid reservoir just for the purpose of collecting these "micro metals." They need to be removed, so they do not re-enter the transmission system and cause more breakdown of the moving parts in the transmission.

When Should You Change the Fluid?

An automatic transmission can go up to 100,000 miles before it needs to have the fluid changed. A manual transmission should be changed before 50,000-60,000 miles. Here's a good article about when (and whether) to change your fluid.

There are a few transmissions on the market that are not serviceable at all. Check your owner's manual to find out if this is the case with yours.

If you want to do this, let's get started. The photos and the video at the end show me changing the fluid on a 1989 Chevrolet 3500.

Parts List

First, we need to get our tools together:

  • 1/2" Socket with ratchet.
  • Screwdriver, or other prying device.
  • Catch basin to collect old fluid in.
  • A funnel.
  • Some sort of deflector if desired (to deflect fluid from going everywhere).
  • Lint-free rag to clean the fluid reservoir and the magnet inside of it.
  • Shop towels, and plenty of them just in case of a spill!

And get our parts together:

  • One new transmission filter (It will normally have a new gasket in the box with the filter).
  • Transmission fluid for your type of vehicle. I used Valvoline Dex/Merc for this truck (Most auto parts stores will be able to look up what your vehicle requires. Don't mix fluids, or use the wrong type of fluid. It can damage your transmission!).
  • Make a gasket, or gasket sealer, if you have a leaking pan.

Step-By-Step Transmission Fluid Change

Here we go! The video below provides the same instruction as you will find here.

You have your tools, and replacement parts ready, right! Ok...

  1. Disconnect the negative battery cable (I know, I know, just be safe and do it).
  2. If your vehicle sets low to the ground; Use a jack to lift the front end and set it on jack stands. Do not leave the vehicle on the jack, use jack stands.
  3. Underneath the vehicle, locate the transmission fluid reservoir pan. It will be the semi-square item with the drive-line going into the upper part of it.
  4. The bolts holding the reservoir on, for the Chevy 3500 are 1/2". Remove all but 3, or 4, of these bolts. Leave the 3, or 4, at one end of the reservoir pan. Loosen them, and it will allow the reservoir pan to lower the opposite end. This will help you reduce the risk of a transmission fluid shower. As you loosen the bolts have your collection container below the reservoir pan to catch the fluid as it starts to pour out as you lower it.
  5. When the transmission fluid has stopped flowing out of the tilted reservoir pan, put your hand under the center of the reservoir pan to balance it. Go ahead and remove the 3, or 4, bolts the rest of the way. Hold the reservoir in position until you've removed the bolts all the way, then use two hands to lower it down.
  6. Empty the fluid from the reservoir pan into your catch basin, and allow the fluid from the transmission case to drip into the catch basin as well.
  7. There is a bolt holding the filter in position, and a tube feeding down into the filter from the transmission. Remove the bolt, and the filter should slide right off of the tube.
  8. Take this moment to inspect the transmission parts, but do NOT touch anything unless you totally know what you're doing!! But do inspect that there isn't any scoring, or broken items. Take a lint-free cloth and wipe the contact edge of the case. Remove any sealant that may be on the edge.
  9. Get out from under the vehicle for a minute and clean the reservoir pan with a lint-free cloth. Remove the magnet and wipe it clean, then wipe the reservoir pan clean. Remove any sealant that may be on the lip of the reservoir pan.
  10. Replace the magnet into the reservoir pan!

Finish It Up

11. Take out your new gasket. Personally, I like to set the gasket on the clean reservoir pan and start 2 to 3 screws at random holes through the gasket before I slide back under the vehicle. (By starting a few screws I know that the gasket is in its proper place when I set it back up on the case. Then I just finish screwing them in. It makes mounting the reservoir pan much easier).

12. Now you have your gasket set how it's supposed to go on the reservoir pan. Slide yourself, and the reservoir pan, AND your new filter back under the vehicle.

13. Set the filter in place, with the tube going into the hole on the filter, and line-up the hole where the bolt goes to hold the reservoir pan in position. Install the filter bolt.

14. At this time, if you have a leaking reservoir pan, and want to put gasket maker, or sealant on it, now is the time to do that.

Scroll to Continue

15. Take your reservoir pan and set it up into position and finish screwing in those bolts you put in back in step #11, the ones holding the gasket in place.

16. Now put in the rest of the bolts, and torque to the specification for your vehicle. The specification can be found in the manual for your vehicle, or online there are several websites more than happy to provide you with specifications.

17. Now your done under the vehicle. Yeah!

18. Remove the vehicle from the jack stands.

19. With the vehicle back on the ground, open the hood, and locate the transmission fill. Pull the dipstick out, put in a funnel, and fill with the appropriate transmission fluid, and amount. Both of these are very important!! The wrong fluid, and over-filling, or under-filling can all damage your transmission! Put the dipstick back in.

20. Start the vehicle's engine, but DO NOT REV it. Move the gear selector through each gear, including reverse with the engine running.

21. Shut the engine off. Get down and look under the vehicle for any leaks. If the reservoir pan is leaking, try to re-torque the bolts.

If that doesn't stop the leak...

  • The rubber gasket may be twisted, or off position. Loosen all the reservoir pan bolts and use a jack to lower the reservoir pan enough to manipulate the rubber gasket and make sure it is in place. Then, re-torque the bolts.

If it still leaks...

  • The reservoir pan may be bent. Loosen all the bolts and use a jack to lower the reservoir pan enough to get some gasket maker in there and then re-torque the bolts.

If it still leaks...I don't know, buy a new reservoir pan?!

When you have no leaks, right on! Either way, check the fluid level again. The filter will have absorbed some fluid since it is new. And you're good to go another 50,000, or 100,000 miles!

Nice work!

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2018 Joanna


WheelScene from U.S.A. on March 02, 2018:

Awesome, comprehensive article thanks for sharing!

The images and video at the bottom help to really explain Transmission Fluid Changes.

We made a post you might want to review and reference!

Thanks for sharing!

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