I order some new drain/fill hardware and the ever-trusty RedLine MT90! Get the car in the air and see dirty fluid on the bottom of the case near the drain plug.
Owner reviews for gear oil
The Redline shockproof gear oil line has performed very well for me in differentials, especially in endurance racing applications where a cooler IS NOT used.
GM Syncromesh seems to be the best.
Ravenol do the awd-h oil.
With a bit of effort, the fill and drain plugs reluctantly spun free of their comfortable homes in the diff. The fluid that came out looked fairly fresh, so in went a bit of Redline 75W90 limited slip gear oil, because this is a true enthusiast machine.
I switched from Mazda oem to redline and it significantly improved the shifting into first and reverse. I'm very happy with redline so far.
I decided on Redline MTL which has a viscosity of about 10.8cst. I can confirm just based on shifting feel alone that I prefer the Redline MTL to that Amsoil MTG. Actually I really didn't like the Amsoil MTG that much based on the shifting characteristics.
mt90 is good shit, i put that in my 280z and it shifts like butter up or down at any speed.
Not as expensive as redline and you can get it locally. I live in New England and it performs well in both hot and cold climates. I've had it for 1 1/2 years now and I love it. Just hate the damn smell of the gear oil.
I will add this, I drove it for 10-15 miles already, and where as the transmission had a bit of a whine at 65 before, now it is really quiet. And it may be placebo effect, but it does feel like it goes into gear smoother than before.
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