I've had my 93WRX for 5 years now. All the time the gear box has felt a bit clunky, hard to get into reverse and 1st.

Last service the gear/diff oil was done at graham goodes and redline put in.
After that the gear box got worse, when warmed up it would crunch going into 3rd, 4th and 5th unless i let the revs die down between changes. Even then it was not right.
I also noticed a whine sound which i thought was from the rear diff when easing off throttle.
I was too lazy until now to bother changing it but finaly got my *** in gear.

After doing some searching on here i decided to try some Castro Syntrax semi synth 75w-90 ordered from opie oils.

I did the Diff first to see if it would cure the whine. Drained it and found no metal filings etc in the old oil. Replaced with the syntrax but the whine was still there.

Just done the gear box (21mm socket needed). Drained and only a very small amount of fine metal filings on the magnet on the drain plug. Stuck the new oil in (took 4 litres).

It is like a new box. No crunching, smooth gear selection and the whine which i thought was from the rear of the car seems to have stopped. I wish i'd done it 5 years ago.

Anyway just a post to help anyone who is searching with the same problem

Thanks everyone

PS: I don't work for Castrol lol