Anybody who hasn't switched to GM synchromesh youre missing out!

Spence

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Hi guys, after doing a lot of research, apparently GM synchromesh fluid is the fave for hondas in general for manual transmissions. So I swapped the honda MTF I put in 500miles prior for the GM synchromesh, the shifting on the car improved massively. Just a big difference. No more notchy kinda thumpy gear changes, just smooth. That honda MTF IMO is no good.

I got the stink eye from honda techs when I put that fluid in lol...
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MrAnderson

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I just swapped to AC Delco Synchromesh FM on Saturday and almost immediately noticed a difference. I was having an issue with 2nd gear crunch/grind in the cold and it's greatly improved. I still get 1 or 2 crunches into 2nd when I leave for the day, but smooth after that. It's only been a couple days though, so it may improve even more.
 

tacocat

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Yes with many fluids that have a friction modifier you will feel an initial change in the shift pattern. But the trans and the diff are not meant to have a friction reducer in the fluid. So long term you could cause more damage to the synchros and the diff.

This topic has been beat to death since the early Honda-tech days back in the early 2000's. Honda mtf works just fine and is designed for hondas. You could throw gear oil in it and it would shift like butter but these transmissions aren't lubricated with a pump, it's splattered. So what happens when you use a heavier fluid? It may not reach all the components. Then long term they fail.
 

MrAnderson

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Yes with many fluids that have a friction modifier you will feel an initial change in the shift pattern. But the trans and the diff are not meant to have a friction reducer in the fluid. So long term you could cause more damage to the synchros and the diff.

This topic has been beat to death since the early Honda-tech days back in the early 2000's. Honda mtf works just fine and is designed for hondas. You could throw gear oil in it and it would shift like butter but these transmissions aren't lubricated with a pump, it's splattered. So what happens when you use a heavier fluid? It may not reach all the components. Then long term they fail.
According to what I've found online, both are a 75w-80 weight. I also have found nothing but glowing reviews for those that are using it. I'm by no means an expert though.
 


danfg2

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Thats what I just changed my MTF with. AC Delco Synchromesh FM....it's butter.
 

EarthPIG_0311

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Yes with many fluids that have a friction modifier you will feel an initial change in the shift pattern. But the trans and the diff are not meant to have a friction reducer in the fluid. So long term you could cause more damage to the synchros and the diff.

This topic has been beat to death since the early Honda-tech days back in the early 2000's. Honda mtf works just fine and is designed for hondas. You could throw gear oil in it and it would shift like butter but these transmissions aren't lubricated with a pump, it's splattered. So what happens when you use a heavier fluid? It may not reach all the components. Then long term they fail.
When I had my '08 Accord I had the 3rd gear pop out issue. Researched the forum I was a member at the time and GM Synchromesh/AC Delco seemed to be the solution. Then came across a post that said this, long term use could damage the synchros so I never made the switch.
Now with this car I have no issues at all and butter smooth shifting sounds so appealing but I'm hesitent to do so based on the reinforcement of what I read long ago.
I know there's people on both sides of the fence and I'm no expert so I'm grateful folks with more knowledge than me post here so I can make the best informative decision
 
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Proxkiller

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I want to switch to it but I’m worried about the warranty, I’m assuming using non oem fluid(s) it would just give them a reason to void my warranty right?
 

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According to what I've found online, both are a 75w-80 weight. I also have found nothing but glowing reviews for those that are using it. I'm by no means an expert though.
There's a lot of placebo effect. People are led to believe that it's the cat's tits, so they manifest a feeling of improvement.

This notion exists in any market. I had a guy bring me a "tube" preamp that he wanted the tubes changed on. Swore they were worn out and everything sounded like shit. I took the amp apart and found that only the 6 volt heaters were hooked up... tubes were literally doing nothing. I told the guy, he didn't believe me and insisted that I do the swap anyway. Did the swap and he swears it's a 100% difference.

A fool and his money....
 

MrAnderson

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An update on the fluid for me…it’s smoother maybe, but it didn’t fix the 2nd gear crunch when cold. I just short shift at 8 MPH and it goes in smooth lol

I’ll probably go ahead and switch back to Honda MTF in about 15k miles or so.
 


TigerSi

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The LSD in our SI is Helical Gear Style with no Clutches is that correct? If that is true then we do not need friction modifiers which are probably super hard moly powders. I would think over time that would not be good on brass alloys. JMHO if Im wrong so be it.
 

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An update on the fluid for me…it’s smoother maybe, but it didn’t fix the 2nd gear crunch when cold. I just short shift at 8 MPH and it goes in smooth lol

I’ll probably go ahead and switch back to Honda MTF in about 15k miles or so.
You know after I got the clutch job done, things were a little crunchy or required a little more effort to put into gear. Just a beefier clutch setup over the stock setup. It was a little notchy to get 1st gear and 1st - 2nd. Some pple recommended switching tranny fluid or heavier shift knob. I thought about it, but stuck with the OEM fluid for the reasons being mentioned in this thread. I thought about a heavier shift knob and I got one, but so far I've not put it on, as I started to get used to how tactile shifting felt and now prefer it. I just shift more firmer. I'm still using the OEM shift knob. I don't ram it into gear, I just use the required amount of effort to put into gear and now it feels natural. I'm very sensitive to changes. So at first, it bothered me, now, after a few months and couple thousand miles, it's really no problem.
 

mis3

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For my 2018 SI Coupe, I have used Amsoil twice and frankly, I did not see any difference.
Next change will be Honda MTF for me.
 
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Design

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I've heard all the arguments both for and against GM synchromesh w/FM. The consensus is that because our LSD is helical and not clutch-type, it should be fine providing it's of a similar weight. Many folks who've weighed in on the technical side of it claim that it's just a hair thinner than Honda's oil. But it's not a miracle cure... often times it's reportedly just masking a larger issue such as a prematurely worn sleeve (which will eventually get worse). Much of the internet hype surrounding GM's MTF was its comparison to the old Honda MTF. Honda's current MTF is really, really good IMHO.

I personally use the Honda MTF and swap every 60K. It requires a little extra TLC when the transmission's cold but has always worked well in the MT Hondas I've owned long-term.

EDIT: To clarify, there are two versions of GM's Syncromesh... one with and one without supplemental Friction Modifiers. The former is what people tend to rave about and is considerably more expensive. But all MTFs reportedly contain some level of FMs.
 
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