Gear oil AMSOIL or RED LINE

TBH, I recommend OEM fluid for the trans for this reason. It's too much of a minefield with hybrid fluids. I used to recommend Amsoil (I use it) but they no longer have the gear oil I use.

I recently replaced my front and rear differential oil with Redline 75W85 full synthetic.

I've used Redline 75w85 which has the Toyota spec listed on the bottle. Have also used ENEOS 75w90 without any issues.

Amsoil makes a 75w-85 severe gear lube but I've always used the same in 75w-90 with no issues.

Under hard driving conditions per the manual reduction gear oil should be changed not just inspected. Almost all off us fall under hard driving. Search around some people have gotten better range out of higher quality gear oil redline I think.

It's hard to find GL4 gear oil anymore. The only real GL4 available in the States seems to be Redline. GL5 oils are generally harsher on brass synchros. I've been using Redline since 2007, when I bought my GTI, and it shifts just as well as it did back then.

Amsoil Severe Gear, it's the best in the business

Amsoil severe gear lasted until ~3200 km, but it started again, but much slower progression.

For me the Redline was crunchier at low temps.

I had tried Redline MT90 to get rid of the intermittent grind into 2nd, but it made all shifting more difficult and always grind into 2nd. So I went back to OEM.