I am currently using the GM Syncromesh and frankly I am not at all happy with it. Shifts seem to be a lot more notchy. I don't get grinds never have but the shifts aren't as smooth as they use to be. I will be switching baack to good ole Honda fluid in the spring.

 

My initial experience with GM synchromesh was great, got rid of all the notchness in the transmission. But, it seems to wear out quickly as I noticed notchness coming back after few thousand miles and on the track started to have 4th gear grind.
I am looking for better replacement. If I there isn't any I guess I will follow RT and turbo_pwr and go back to Honda fluid.

 

To add to the above, I've tried the GM fluid and have gone back to Honda MTF, when up to normal operating temps the Honda MTF is perfect for me. It also works fine in our cold Canadian winters.

 

The RL MTF is too thin for my liking but the heavier RL MT-90 is my favorite so far for my driving conditions.

Since you have not tried all of them I would be careful in giving impressions.

I think everything you mentioned has some synthetic content and I'm not sure it is a good indicator of how long the lubricant will hold up in the transmission. It appears to me that this transmission facilitates viscosity breakdown pretty quickly with an impact on shifting smoothness.

But like all the things we discuss it depends upon your use of the car.. I would think that high rpm in the lower gears would be the most demanding, and moderate speeds in the higher gears the least.

 

thanks everyone for the input/impressions/opinions!