Changing the gearbox and rear diff oil next week. Been down an absolute rabbit hole online trying to find the best option so just going to ask for some thoughts here! I have a 1994 WRX import

Currently planning to buy the Castrol Transmax Universal 75W-90 stuff from Opie, have got a bit of a grind/crunch when pulling into 2nd gear and read a lot that this oil will help!

Anyone have any thoughts otherwise or even just agreements? Would be great to hear before dropping £100 on oil lol

(p.s. please drop your regular engine oil recommendations below too as that is also a job for the weekend)