Originally Posted by VoodooShot
Did I just waste 44$ in my 99 ax15
Guy said yes it'll work cause book said gl5
. I changed when I got home , now I see it's suppose to be gl4 .
Older books were incorrect when they said to use GL-5, it needs to be either GL-3 (hard to find) or GL-4. GL-5 is not recommended because most (but not all) GL-5 gear lubes have sulphur-based additives which are harsh on yellow metals which includes the transmission's brass gear synchronizers.
So yes, get that stuff out because Valvoline Synpower is sulphur-based but it won't do immediate short-term damage so no worries.
Yes you can use a synthetic 10W-30 motor oil, the manufacturer of the AX-15 added that to the list of approved gear lubes several years ago. No worries, 10W-30 motor oil has essentially the same viscosity of 75W-90 gear lube because motor oil and gear oil are measured on two different viscosity scales.
Or use Redline MT-90 which is a synthetic GL-4 75W-90.
There are a few GL-5 75W-90 gear lubes that don't use sulphur-based additives and are thus safe for transmissions but it's easier to just use Redline MT-90 or, easier yet, just a good brand of synthetic 10W-30 motor oil. Yes that really is approved for use for the AX-5 and AX-15 transmissions and it works well in them.
If you do ever pick up a bottle of synthetic 75W-90 GL-5 gear lube and it says safe for yellow metals (brass synchronizers), it's fine for use in the AX-15 and AX-5.