Manual tranny fluid change ?'s
 

Using the "search" function on this and coming up with older threads. Looking for something more topical, I hope!
First: What size are the 2 plugs (socket size)?
Second: Toyotal calls for GL-4 or GL-5 and after buying 2 qts of Royal Purple (expensive at 1/2 the price), I read that GL-5 may be harmful to the synchros.
Any help is appreciated! Thanks.
Socks

I wanna say the plugs are 22mm, but not positive. I just changed mine not to long ago, that's what's sticking in my head.

About the oil, not sure on that either. I used ams oil the first few times and this time I got lucas oil. I just make sure it's synthetic and 75w-90. My car's been good to me since 30k miles with that oil and now it has 110k miles on it.

Sorry I couldn't be more sure, lol.

GL-5 gear oil is designed for hypoid (spiral cut gears) differentials which shear oil. It contains extreme pressure sulfur compounds which can react with the copper alloy parts (brass or bronze) in transmissions. Older transmissions contained such yellow metal parts as synchronizers and bushings, and these could react with sulfur to be etched into copper sulfide. My 1971 BMW 2002 had such syncros which wore out by 40,000 miles because everybody used GL-5 which was the usual gear oil.

Nowadays, transmissions don't have such syncros, and can use either GL-5 or sulfur-free GL-4. But GL-4 does not give the wear protection of GL-5.

I don't feel like looking for the thread but an old thread on here someone contacted Scion directly and was told by them in an email that GL-4 was recommended due to the GL-5 attacking the bronze