Has GL5 oil damaged my GL4 gearbox?

Question

I have a 350z and the gearbox uses GL4 gearbox oil, my mechanic put in Syntrax which is GL5 but states it can be used for GL4. When I 1st drove it with the Syntrax the gearbox felt fine but then I started to notice more and more friction, it was put in about 1200KM ago. I can feel things rub when I change gears so it is not as smooth.

Seeing as though it is a progressive thing my logic tells me its done permanent damage to the synchros, could this be true?

Answer 1

no, it has not done permanent damage, if it has, then sytrax can be sued. Most likely the level is a little low, and the gl5 is intended for tighter tolerances, similar in some ways to running 5w in an engine designed for 20w.  

Answer 2

I don't see where your going to have any log term damage. If you don't like the way it fill's ,get it changed back to the GL4 ,The only other thing besides the syntrax being in one of them is that the GL4 must be a little sticky  to help inhere it to the gear's .( Be safe have it changed )

Answer 3

Call the Castrol Tech department at: 0118 984 4321

Ask if GL5 can be used in your car.  

Answer 4

GL5 oil has a high sulfur content that corrodes yellow metals like bronze. If your gearbox have yellow metal parts, they will not last very long. Best to change out for the right thing.