I've got another thread on the go with trying to fix some super notchy shifting...I'm going to replace my clutch master / do some more work cleaning bleeding the OEM one.

With that, I recalled I have 5 bottles of Gm Synchromesh FM in my attic that I've been saving for a rainy day...I ran it in my Honda Beat years ago and it did wonders.

I can find threads on the GM Synchromesh having almost unanimous positive feedback...but I can't find any long term feedback if there are any issues. There are some honda forums that warn against damage to brass bits (syncros) but there is very little information on this.

Anyone running the GM Synchromesh FM for a while? How has it been?

 

Should be fine. As long as they're not like 10 years old or something.

 

The purpose of a synchromesh type of fluid is that it is supposed to be friction modified to aid synchros. As long as it isn't a GL-5 fluid it won't harm brass synchros. , I'm pretty sure it is a GL-4 or less. If you decide to use it make sure to give the bottles a good shake, the additives may have settled to the bottom of the bottles.

Saying that I would suggest Amsoil MTL (5w30) fluid, it works wonders in the Honda tranny. I did use the GM synchromesh fluid back in the day and it didn't help with my 1-2 shift for very long, it seemed to deteriorate quickly. The Amsoil was far superior, I tried a number of fluids from Redline MTL , GM Synchromesh, Penz. Synchromesh , and Amsoil worked best.

 

I checked their site and see the Amsoil 5W-30 Manual Synchromesh Transmission. I am assuming this is the one you use as it is the only one I see. I was thinking of trying it out.

 

I ran GM synchromesh in mine when it was exhibiting some notchiness and wear from track use. IMO it was the worst of the ones I tried (Honda, Redline, GM). Some other honda owners seem to think it is great but was not my experience. Mine eventually got the 2-3 grind (worn synchro) and I just found a good used unit and all was good and like butter again. The notchiness and grinding described in the other thread is not going to be solved with any type of fluid. It is a hydraulic or synchro issue given the severity of it described in that thread.

Fluid type may make a slight difference in how it feels but grinding on shifts, hard to get into gear, etc is beyond that assuming a complete wrong type of fluid was used to start with.

 

I have been using Amsoil for a number of years after trying out several including Honda MTF. I change out every year just because I like to. Amsoil has been good to me so far with fairly smooth shifting cold and butter when warm. I do not see the weight of the oil on the bottle. I see no reason at all for me to switch to something else. My bottle here, which I had Amsoil ship to me with some other products in March, looks different than what is on the website now.

 

Thanks for the reply! I

 

FYI Honda's MTF is a synchromesh fluid, where it differs is the viscosity. It's the equivalent of a 20 weight engine oil. The other synchromesh fluids have higher viscosities, with royal purple being the thickest by far. If you've ever taken apart one of these transmissions you know how small the oil distribution holes are. It also makes sense why Honda chose a low viscosity synchromesh fluid. Not saying a higher viscosity isn't safe, just that it explains the cold start notchiness of those non Honda MTFs.

 

Using redline at the moment, and it works very well, i will give amsoil a try after all this good reviews.

 

If the MTF fluid for Amsoil is 5W-30, that is pretty darn thin at start up cold. You can go to 0W-30 and that is what I use for the engine in a synthetic just for those cold start up reasons. I would thing a 5W at start up will go through those small holes just fine if not better than Honda MTF.