At the moment I'm on redline 75w90 NS, recommended over the standard redline 75w90, as it is not as slippery and more suited for our transaxle. At least that is what most people said.
Here's the full story behind my gbox rebuild that leads me to use RedLine 75w90 NS:-
Originally, I have my gbox rebuild to fix my mysterious issues with the 1st gear not going in as well as grinding reverse gear problem. Well rebuild here is mainly taking the box apart and replacing them with new synchro.
After rebuild, problem still persist! My mechanic decide to add some sort of addictive to improve the slippery of the gear oil. This is a bad choice as it turn out, the extra slipperiness render the synchro ineffective, and I end up grinding when I shift in any gear at high speed (yes, including shifting up). This as I describe was my second issue!
After some googling, I learn that everyone recommends me to switch to Redline. That is what I did. The shift has gotten better, but still grind if I down shift at speed above 20-30 kph from 4th to 3rd and 3rd to 2nd. One important note is that, my mechanic did not completely flush and clean up (is there such a way) of the existing oil before swapping to Redline. Not sure if this is the issue, as he have tainted the Redline oil with some old problematic oil that still sticks to the metal. I'm now in a dilemma for my next gbox oil change to either switch back to what is recommended originally for our transaxle (possible valvoline) or get a new batch of Redline and cross my finger!
Since we at it, let me explain why I suspected that my first problem (cant shift to 1st and grind when reverse) some what got to do with master cylinder. When I first got the car, I can at most drive like half an hour, before
the problem appears. That is how I associate it with heat.
I did plenty of things to the gbox and stuff, nothing fix the problem. Problem still persist, and after half an hour of so, I have no first gear and risk losing my reverse gear! Couple of months ago, my MC failed, and got myself a new one from ebspare. Now, on a hot day, I can last at least an hour before the problems creep up again. You see where I'm coming from?
what oil are you using?
people recomend redline 75w90, which iv got right now. while its ok, its not great and with a fresh gearbox i still got a little grinding.
the valvoline gear oil i used in my gtv is better stuff i think.
maybe youve got the wrong oil all together? i couldnt think it would be anything else going by your info.