gl-4 or gl-5 tranny fluid

[goatman]

I've got an old 84 subaru wagon thats got a 4spd and the syncros are really bad. About 2 years ago I drained the old tranny fluid and put in Red Line 75-90NS, its the gl-5 manual tranny stuff.
Now I hear on this site that the gl-5 is bad for your transmission? So should I drain it and put in the MTL90 thats gl-4? The 75-90NS helped but it still grinds when downshifting to second, so do you think the MTL90 will make it shift any better?

 

[Ken2]

Many modern GL-5 gear oils are safe for the yellow metals in a gearbox, so GL-4 oil isn't needed in these cases. I don't know the specifics about Redline nor your gearbox.

"Non-corrosivity to brass, bronze and other non-ferrous metal parts," from Schaeffer's Technical Data sheet for their #209 GL-5 Moly Universal Gear Lube.


Ken

 

[Rebel Rouser]

Red Line's MT90 GL-4 manual transmission lube may provide better "traction" for the synchros to operate effectively, although you state your synchros are already bad.

I'm currently running Amsoil's Series 2000 75W-90 gear lube in my Dodge truck's NV4500 manual 5 speed. It's rated GL-5 and they assured me it is compatible with yellow metals, however, I'm having trouble shifting between 1st and reverse at low speed now, so I'm guessing it's a tad too slippery for the synchros. It doesn't grind, I just have to use both arms on the shift lever to get these gears engaged. It didn't do this with the factory fill, which was a GL-4 rated lube. Red Line MT90 is what I'm going to try next.

 

[Bror Jace]

Reb, your experience is the reason I won't use a gear oil in a tranny unless it specifically says "syncromesh" on the bottle.

For example, as good as Schaeffer #267 might be in differentials and roto-tillers, I'm afraid it's too slippery for my Nissan's 6-speed tranny.

Red Line loves to use moly in their engine oils ... a LOT of it. But they don't use any in MTL or MT-90 according to the samples tested I've seen. I'm sure there's a good reason for this.

--- Bror Jace

 

[widman]

According to my Check-Chart manual, Subaru recommends GL-5 for all except the Justy (GL-4).
It's not only the yellow metals, but the grooves and surface area of the synchronizers, as well as the angle of contact.

 

[Gary Allan]

Maybe someone can help me out with this anomoly here. Now I know that brass has been used in every trans that I've ever broken down. I've replaced many brass blocker rings and synchros ....................and the only thing that was put in the trans is 90 weight hypoid.

NOW-my 99 AX15 needs not GL-5 ..not GL-4 ..but GL-3. Did the clown that made DC autos require a special ATF (allegedly that antifoam crap)...get to redesign/re-alloy the soft metals in the manual trannies as well???

 

[widman]

Good luck. I don't know of anyone producing a GL-3. It is banned from sale here.
If it is the brass and other yellow or soft metals you worry about, stay with a Borate additive package as used in Delo Gear Lube and stay away from the Sulfur/Phos. additive packages.