| max gear 75w 90. I have tried 75w 90 synthetic in Amsoil, Mobile 1, Valvoline, Redline MT90 and only the RP gave the quietest operation and best shifting. I would replace the Coastal (see below). Back when I was researching gear oils I contacted Huldecki at Valvoline racing tech dept who stated that gear oils rated GL3,4 or 5 are not a manual tranny rating but a multiple rating for rear differentials that was developed to make the gear oil acceptable for use in older differentials that were designed when only GL 3 and then 4 rated gear oils were available. As differential gearing designs improved with higher Hp engines and gear tooth shear stresses increased a different spec gear oil was required so GL 5 came out that had greater HP additives (take that as smell worse). The GL 5 was marketed to be campatable with older differential gearing thus the multi rating was developed since the additives were considered non destrictive to the older designs and there were still many on the road. Valvoline did admit that the multiple GL rating is confusing to the general public. And they recommended to me not to use multi rated GL gear oils in a manual tranny and only use the gear oil rating specified for the manufacture. In the case of the Z32 a GL4 rating. However there are some gear oils that have a multiple GL rating that can be used in manual trannies because these gear oils have been specifically designed with low corrositivity in the additives thus no damage to softer metals used in shifting syncronizers yet still provide the needed stress protection. RP max gear oil is designed with low corrositivity and that is key why it can be used in the Z32 tranny as.
ZUL8TR in Orlando,FL |
