Mixing amsoil MTF and MTG

[JHZR2]

If wanting a fluid thinner than amsoil mtg but thicker than mtf, any issues or concerns with combining those? Mtf is called synchromesh, mtg isn't, though it seems that "synchromesh" is a viscosity range.

Is the chemistry in mtf and mtg identical?

 

[mechtech2]

I am considering the opposite - since I have zero winter problems with straight MTF, I was thinking of swapping in a qt of MTG to go a bit thicker.
I do not know if the adds are identical.

 

[cos]

I'm currently running Amsoil, one qt MTF and two qts MTG. My trans shifts great in all temps.

My previous fill was Redline (one qt MTL and two qts MT90). Shifting was also great with that mix too.

 

[Pablo]

The additives are not identical, but they mix fine. It's what I run in my 850 Volvo 5 speed. I run 60/40 MTG/MTL. Have for 4 years now, works great.

 

[MolaKule]

Quote:
though it seems that "synchromesh" is a viscosity range.


Synchromesh is not a viscosity but a type of gear engagement system for manual transmissions.

The two fluids can be mixed to get the viscosity you need by experimentation.

They contain the same synchro friction modifier compounds and similar Anti-Wear additives; just different viscosities of base oils.

MTL or MTG can used in all kinds of synchromesh-type transmissions that use low or high viscosity fluids.

Historically, I think the reason the lighter fluids has been seen as the "synchromesh" fluid is that GM's original synchromesh fluid had a viscosity of about 9.5 cSt, so any MTL between about 9.0 cSt and 11 cSt is seen as a synchromesh fluid. And then of course, Pennzoil and Texaco picked up on it with a similar fluids.

Many VW and Toyota transmissions require a 75W90 fluid but have synchromesh type ystems as well. Even some of the heavy duty truck transmissions have synchromesh type systems as, but may use 50 weight oils.

 

[JHZR2]

Thanks. Are there any passenger cars out there (recent ones) that are NOT synchromesh? If so, what kind of fluid do they use? What is the difference in gear engagement and synchronization?

 

[mechtech2]

There are some manual transmission cars made with non synchronized reverse gears.
But everything else has synchros for the forward gears, for decades.

This allows us to put it in any gear without needing to manually rev match the engine to the proper speed for each gear's engagement.

Gears in a manual trans are always engaged and meshed. Power flow to them is allowed by the synchronizer /clutch assemblies.

Good trans fluids have additives that let the synchros bite and grab better - they are friction modified for this.

In general, a 'SYNCHROMESH' gear oil is a manual trans lube that is designed for good shifting, and is a bit lighter/thinner than normal gear oil.