I am getting ready to do my gear boxes on my 98 TJ. D30/D35 I know takes 80-90 gear oil, the transfer case takes ATF/Dex, my question is about the AX15. According to the service manual it takes 75-90, I am wondering if I use 80-90 will it hurt anything.
I spoke to the guy at Dodge who used to be a mech and he said he thought it was supposed to take 80-90 since all the other AX15's before it did. When he looked it up in the service guide he saw it was 75-90. He told me the only difference between the two was 75-90 is synthetic and 80-90 is not. He did not know what had changed to require the 75-90.
Anyone got any input on this? I have to go to the parts store to get supplies and if I could just buy the 80-90 and use it in everything it would save me some cash.
Thanks for the help.
4.0L, 5spd, 4.25 Zone lift, Currie Anti-rock, Trutrac D30, D-locked D35 w/4.56 gears, MCE GEN I Flares, 33" Trxxus ATs, Engo 10K# winch, rear disc brake conversion.
My idea of help from the man above is a sniper on the roof.
I agree with KBR97 the actual manufacturer of the AX-15 transmission, Aisin, changed the spec oil to 10w-30 because the 75w-90 is bad for the brass synchros.
10w-30 and 75w-90 have the same viscosity, they are just measured on different scales for gear and engine oil. 10w-30 doesn't have some additives in it that the 75w-90 does that is bad for the tranny, such as sulfur.
I agree with KBR97 the actual manufacturer of the AX-15 transmission, Aisin, changed the spec oil to 10w-30 because the 75w-90 is bad for the brass synchros. .
No Aisin did not change the spec to 10W-30, they simply added synthetic 10W-30 as another acceptable lubricant.
75W-90 by itself is not bad for the transmission, only those GL-5 formulations of 75W-90 that are sulphur-based are bad. GL-3 and GL-4 75W-90 gear lubes are fine, Redline MT-90 is a GL-4 75W-90 and is a superb lubricant for the AX-5 and AX-15 transmission.
And yes, 10W-30 motor oil and 75W-90 gear lube are actually very similar in their true viscosities. Motor oils and gear lubes are measured on two different viscosity scales so while their numbers are far apart, they are actually very similar.
And some (but not all) synthetic GL-5 75W-90 formulations are ok for the transmission with Royal Purple's GL-5 75W-90 being one of them. The GL-5 75W=90 gear lubes that are safe will include words to the effect "Safe for yellow metals" which means its GL-5 formulation is not sulphur-based which means it will not attack the brass gear synchronizers like conventional GL-5 gear lubricants will.
__________________ Offroad until Sunday! When you have a choice, buy American.
just changed my gear oil today.i used the Redline MT-90.i was only able to get just over 3 quarts in.my 4th quart is about half an inch below where the neck meets the bottle. i think there is enough in there. according to the FSM the Correct lubricant level is from the bottom edge, to
no more than 6 mm (1/4 in.) below the bottom edge of
the fill plug hole.
where is the bottom edge that they first refer to?
will i be safe running at the level i'm at?
yes i was on level ground.
shifts better already.
i imagine i am between 3 and the recommended 3.27 quarts