Skip to main content

How to Inspect The Transmission Fluid on a Used Prius

Looking to buy an older model used Prius, but not sure how to inspect the transaxle fluid to see what kind of problems may be lurking in the purchase? Here’s an informative video by a popular Toyota Maintenance channel that demonstrates where to find the transaxle drain and filler plugs and what the color in the transmission fluid could look like after 176,000 miles, telling you something about the car’s history.

Is That Used Prius a Keeper?

Buying a used car can be difficult especially when you know nothing about its maintenance history and the kind of driver(s) that previously owned it. However, there is some pleasure in buying a used car in that you might find a diamond in rough that others have passed on simply because it looked too old and dirty on the outside to warrant any investigation into it.

Cosmetics aside, however, taking the time to do at least a cursory inspection of a used vehicle can help you decide whether that used car has potential; is a problem; or, is potentially a problem. In this article we will take a look at the Prius transaxle in particular.

A Transaxle is a combination of the transmission, differential, and ancillary systems around the axle that have been integrated into one assembly. You will usually find a transaxle system in cars where the engine is placed at the same end that drives the wheels. The operation of a transaxle is essentially the same as that of a regular transmission, with the difference being that instead of connecting a long driveshaft to the rear axle, the transmission's output shaft drives a large gear that meshes directly with the differential's ring gear. In other words, the transmission/drive system are all contained in one box.

With this in mind and including with your cursory inspection, you may benefit by getting underneath the Prius and removing the transaxle drain plug momentarily, as you collect a sample of the transaxle fluid for a visual and olfactory sniff test that can be diagnostic for a potential and expensive problem. In fact, if the transaxle has been overly damaged, a replacement can run between $3,000 and $6,000 with another $800 to $1500 in labor added to the bill.

Both the color and smell of the transaxle fluid can reveal whether there may be problems with the transaxle system, which will be discussed in videos below. But for now, just know this color coding of used transmission fluid problems.

If the Collected Used Fluid is:

Red and Transparent---this is a like-new condition of the transaxle fluid and a good indication that a vehicle has been maintained.

Light Brown and Semi-transparent---this is still a good indication and there is no need for an immediate changing of the fluid.

Dark Brown and Opaque---this is what you will commonly see in a used vehicle. At this point enough oxidation from its long miles of use tell you that it’s time for a well-deserved change.

Very Dark Brown of Black---this fluid has never been changed and could be an indication of some serious wear on the transaxle. Proceed with critical eye on this vehicle before reaching your final buying decision.

Light Pinkish---a major indicator of trouble here as either coolant and/or water has gotten into the system, necessitating a transmission rebuild or replacement. Definitely expect a large repair bill.

How to Check Transaxle Fluid

But wait, can’t you just check the transaxle dipstick and not bother with going under a vehicle? Yes, you can. However, it is not unusual to find an older model Prius vehicle that has a magnetic transaxle drain plug designed to trap bits of metal that may be present as a transaxle wears down or is abused. By going under the Prius and getting a good sample of the fluid and an idea of the amount of gunk settled at the bottom of the transaxle, you can also take a look at the magnetic drain plug and see if there is an unusual amount of metal wear present.

That said, let’s get to the nitty gritty of the Prius transaxle and watch this very informative and entertaining Toyota Maintenance YouTube channel to learn where the drain and filler plugs are located, plus what plugs you could accidently mistake as being the correct ones to remove that could make a mess of things during your inspection.

2008 Toyota Prius Hybrid Transaxle Fluid Check

Changing the Prius Transaxle Fluid

Now that you have a good demonstration of how to find, access and remove the drain plug and collect a sample of transaxle fluid for inspection, let’s take this a step further with another video of the same model of a Prius and learn how to finish the job by changing the fluid that is simpler than you would imagine when a fill plug is located not under the hood, but under the engine.

2008 Toyota Prius Transmission Fluid Change

And Finally…

I hope that you have enjoyed this article and the videos. If you have ever worked on the transaxle or have any experience with Prius transaxles, please let us know in the comments section below.

Be sure to watch for more articles about vehicle maintenance and repair to help keep you informed of what to watch out for and what you can do to ensure that you remain safe on the road and have a good automotive experience.

And it you decide to take your Prius or any other vehicle to a service center to check your transmission or other fluids for you, be sure to check this warning out first.

COMING UP NEXT: How Some Car Repair Garages Hide Their Brake Repair Scam

Timothy Boyer is Torque News Tesla and EV reporter based in Cincinnati. Experienced with early car restorations, he regularly restores older vehicles with engine modifications for improved performance. Follow Tim on Twitter at @TimBoyerWrites for daily Tesla and electric vehicle news.


KEVIN L MORRIS (not verified)    December 10, 2022 - 1:24AM

Prius transmissions do not have clutches. There are NO friction materials in them what so ever.
This means the fluid should NEVER darken unless there is something wrong.
EX: If it is brown, it has been overheated.
If it is blackened in the least little bit, walk away! The surfaces of the gear teeth have been worn off or there is a major lubrication problem.

There are NO repair parts available and your ONLY options are to put a used one in from a low mileage wreck or buy a new one (if it's available).

Ghulam Rasool Khatti (not verified)    January 18, 2023 - 7:52AM

What about transaxle oil for Toyota Aqua
How can we check and verify either filled oil is okay or need to be charged..