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Discussion Starter · #1 ·
I changed the diff fluid on my 2021 CVT this weekend after reading up on the forums. Went mostly smoothly but ran into a few things nobody mentioned, so I wanted to post what I learned. Mileage was 24k, was running the factory diff oil up to this point. The oil was dark brown with a hearty dollop of metal shmoo on the drain plug magnets.

Fill & drain plug specs
My front diff has 8mm internal hex for the fill and check, and T70 for the drain. Rear diff has 10mm internal hex for both plugs. The front fill took some force to get off but not as bad as others on the forum have said. I had a 2' breaker bar and it wasn't hard. Torque spec is 50 Nm on all plugs except the T70, which is 70 Nm. All plugs except the rear fill have washers, which I reused (I'll update if anything leaks 馃榿).

Access
Access to the front diff fill is a bit tough, there is a large metal plate almost directly under it. I could get the ratchet/breaker up near the diff in the space between the plate and the diff, then observe from the wheel well side. On the back you will need a ratchet extension to open the fill, otherwise the head of the ratchet hits on nearby parts.
I think a transfer pump or bottle-bags are absolutely necessary for this. There isn't enough space above the diffs to get a rigid bottle in and tilted. I had a bottle-bag and was able to squeeze it "uphill" like a ketchup packet, but also had a pump and ended up using that for the rest.

Avoid splashing the oil when you drain it
As everyone says, make sure you can crack the fill/check ports open before you drain. But, leave the fill/check plugs threaded in when you open the drain. When I did the front diff, I had all the plugs out and the oil came out like an avalanche. It's a big drain and it points straight down. This resulted in a lot of oil splashing out. On the back, I cracked the fill plug but left it in while draining, and it was much more civilized.

Don't drop the oil bottle cap in your diff
I wanted to do a "test fit" of the diff oil bottle in my diff to avoid spilling anything. The nozzle has a plastic cone on the tip, which I left on for this process... DON'T. The plastic cone came off inside the diff! I left it in there, the logic being that everything in there is way stronger than a small plastic cap, but I sure feel dumb about it. Will update if anything happens, I've driven 100 miles since with nothing so far. The nozzles on the oil bottles are sealed until you cut them, you don't need the cap on to do a "test fit".

Feel free to ask questions and/or call me dumb for the plastic cap incident 馃槕
 

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2018 Sport Hatch 5-Speed Manual
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Mine just turned over 30K miles and I will be doing this as soon as it warms up. My car is a manual transmission, so the front diff will encompass the transmission fluid as well.
 

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Discussion Starter · #4 ·
Now that you mention it, I do think the rear was darker, but the front definitely wasn't golden. Maybe medium-dark brown. The rear was a pretty opaque gray IIRC.
 
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