I have a 2004 (all stock no mods) and realized I have been using Valvoline GL-5 75W-90 for the transmission fluid and saw a thread stating that GL-5 will damage the transmission synchros. Performing basic research it looks like the nubs of the synchros could be worn or the inside ribs of the synchro would be damaged.

The 2004 owners manual states: Genuine Nissan Manual Transmission Fluid (MTF) HQ Multi 75W-85 or API GL-4, Viscosity SAE 75W-85 or 75W-90.

I haven't seen any metal in the fluid at 30k and 60k, I don't powershift and don't drive it hard. I skip gears fairly frequently (1-3, 2-4 etc.) but make sure I'm in the power band. I never have difficulty going into any gear (not notchy).

This might be a trivial question, but should I drain/fill the MTF with the correct Nissan GL-4 now or wait until 90k? Also, could I have already damaged the synchros and not know it? I plan to keep the car as long as possible and I"m thinking I better do it sooner than later. Any help is appreciated!

 

Not an expert on the topic, but if it were me I would change it ASAP for piece of mind.

I changed my fluid when I bought my car at 80k, and next month it will be at 90k but I was grinding gears due to shifter mis-alignment so I will be flushing the fluid again just to clean it out and to use 75w-90 rather than 75w-85. I think I am going to give MotylGear 75w-90 a shot

 

the 350z doesn't have the most effective synchro design from the factory, so anything you can do to help them function properly is not a bad idea.

 

thanks much, the nissan dealer thinks since I'm not seeing any symptoms I'm probably ok..he stated that cold climates are the primary reason for GL-4. Since I'm planning to keep it I'm going to go ahead and change to the Nissan MTF 75w-85 for peace of mind.

 

The real reason is there are brass components in the synchros that are destroyed because of the sulfur in GL-5. I know this because I need to replace my tranny.. out of warranty

Do people shell out upwards of $2k for these things?

 

just curious, how many miles did you have before you found out they were destroyed? I have 70k on mine but am not showing any signs of wear.

 

I have an 03 with almost 60k. The redline did help a little. It doesn't grind unless I drive like an *******, which means that the gear now works when I need it to. Hopefully this will last a little while.

 

Who told you this at the dealer? Your probably ok with gl5 when a gl5 eats brass? Is that moron going to replace your trans when your syncros are trash? Use the correct fluid. Always always look at any type of oil rating if it says gl3 or gl4 dont assume gl5 will work. Oil is just oil. I recommend red lines mtf. Says specically right on their site for the 350z.