Rear Differential Fluid Change on Prius AWD

Since my 2021 Prius LE AWD just went over 25,000 miles, I decided to change out the fluid in the rear differential. (Every 3-years or 25,000 is my rule.)

In comparison to the rear diff in my Tundra, the only thing similar is that it has a drain plug and a fill plug...amount of fluid and fluid type isn't the same.

Tools: Two crush washers (90430-A0003), a 10mm Hex socket (a short one is better but you can manage with a regular one), and 2 Qts of Toyota WS transmission fluid. (You'll use about 1.4 Qts) A pump to refill the fluid or a funnel with a long hose, which is what I did since I hate those pumpers.

Get the car up on jacks or a lift, needs to be level. Remove fill plug which is on the passenger side and a bit hard to spot...not a lot of room in there. I used my 3/8 socket with a short extension. (The 10mm bolts can strip pretty easy to make sure you have it seated in there very good before cranking on it.) Then remove the drain plug on the other side, a bit lower, and drain all of the red transmission fluid. Note: Toyota must have gorillas to install those fill plugs...they are always super tight when it's the first time of servicing.

Note: I've never seen a drain plug with no magnet on it but mine didn't have one. I'll probably buy a replacement with a magnet for next service.

Replace the crush washers and I think the torque spec is 29-37 ft/lbs but I just give it a good snug pull and watch the washer get crushed. Fill with the WS until it overflows. (Be careful to ensure you get over a qt in there...you can get a false reading with it coming out since there's not a lot of room and the air can push fluid out.) I move the hose around a bit when it's almost full to ensure I get it full.

Note: I did it at 25,000 miles but, from now on, will go 50,000 miles...the TS oil that came out was very, very new looking...which is good.

 

Good question...so I pulled out my unused (worthless) Warranty and Maintenance guide from the glove box and had to search for a bit...it does say, at 60,000 or 5 years to replace if tow or hauling stuff and never in the regular section.

One funny thing in there a lot is "Re-torque drift shaft nut (AWD)" and not a single Toyota tech/mechanic I've asked said they've ever found one lose...not even The Car Care Nut on YouTube. (I asked him when he used to do live Q&A sessions.) But, yeah, it says to go ahead an wait 10,000 between oil changes...nope.

 

Wow does it really say 144 months (12-years) before changing spark plugs? Nope. 100,000 miles or 10-years is a good rule...even when you have a pretty big job of removing a ton of stuff (wipers, plastic and metal cowls, exhaust manifold, etc.) to get to the 3 back plugs in the V-6's. For the 4-cylinders, it's usually a 30-minute job even when you have to remove parts of the wiring harness on the old 4-cylinders to get access to the coils. For me, the scariest part is those crappy plastic clips (ignition coil connector)...SO easy to break the tabs so I keep a stash of spares for that reason...they are not hard to replace when you know how.
My 2014 Tundra hits 10 next summer so I'm already planning on a 100% inspection and, probably, replacing, a bunch of stuff....belts, plugs, hoses, caps (radiator and fuel), etc. With OEM stuff, of course.

 

The rear motor in the AWD is very easy to access and drain and fill. As with most rear areas, there's not a whole lot of room to get the quart of Toyota WS transmission fluid up there for the refill, even with a pump, so I used a funnel with a long hose and stood on the right side of the car to pour it in and stopped when it started coming out. (Took about 1.4 qts to refill)
You'll just need a 10mm hex socket bit, two crush washers (90430-A0003), and two quarts of Toyota WS transmission fluid.
As with most 10mm hex bolts, they can be in there very firmly so ensure you have that socket seated as far in there as you can get and might need a breaker bar, especially in older or rusty vehicles. (My daughter's 2012 Sienna was a real bear to break free.)
I changed out mine at 25,000 miles and inspected what came out so I'm changing my service from 25,000 to 40,000 miles...it was super clean coming out.
If you don't have a funnel with a long hose, this is what I used...(and use the same one for the transmission oil change in my 2017 Prius...just need another set of eyes underneath to watch)