To Gear Oil Freaks,
I've tried about all the different gear oils out there, and I totally believe there are
advantages of going synthetic. One thing I've noticed though, is that not all synthetics
are created equal. Nissan trannys do not like overly light viscosity gear oils. I had no
luck with "ultra-light" stuff like ATF, or even Redline MTL. I believe you need
some thickness(cling) to keep lubrication of all the gears and synchros. Also, extra
thickness helps to absorb the shock-loading of aburupt engagement or hard acceleration
over rough pavement. 240's have an inherant sloppiness in the driveline, and those
qualities are magnified(sound) with thinner gear oils. I have had excellent results
with Redline Synthetic Products over the years. From my experience with their products,
the recommendation I have for all 240 owners is:
Redline 75w-140NS for the transmission (excellent for old synchros)
Redline 80w-140 for the rear differentials
I have used this combo on my car for many years. Even with lightning fast shifting and
occasional mishaps, my tranny showed no signs of fatigue or wear. (I cracked it open to
check and change seals.) I am currently testing the REDLINE Heavy Weight Shockproof Gear
Oil in the transmission, because it offers additional shock-loading resistance. So
far so good... I hope this information helps.