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Discussion Starter · #1 ·
One of our local racing guys and motor builders has started running valvoline full syn dex/merc atf in his.

I drove his and it does shift much smoother than my new unit. Clutch seems to grab well, much smoother engagement.

My concern would be clutch life. In a way, it seems like it might be the perfect fluid for the yxz. Thinner. Full synth. Made for a wet clutch pack.

Thoughts?
 

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I would never use ATF in mine. And Yamaha never suggests that as an option.
 

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Yamaha specs multi-weight motor oil. Japanese manufacturing firms, especially ones with excellent reputations like Yamaha, are not known for hiring and retaining incompetent engineers. If they spec a certain variety of lube, there's a reason for it.

Best case scenario, that trans fluid is no worse than the spec'd fluid. Worst case, long term permanent damage to the clutch and/or trans. Trans oil runs much thinner and I would be worried it wouldn't hold up to the heat and compression, especially after it gets "contaminated" with clutch material. Remember, manual trans in autos run gear oil, not trans oil, but they tend to be dry clutch. I'm guessing multi-weight engine oil is thin enough to lube the YXZ clutch effectively but still has visco characteristics that protect the trans gears as well and holds up to clutch material as a solute.

Me? 10w-40 Mobil 1. Meets the specs required for the trans and is fine for the engine as well, letting me buy one bottle to change both.
 

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Discussion Starter · #8 ·
All true, except many manual trans run atf in them.

I just found it interesting.

I am not familiar with any manual trans that is spec'd to run *automatic transmission* fluid. Mind educating me?

Ford trannys made by Mazda. A lot of dodge manuals. A lot of tuner guys also run the type F trans fluid for less drag.
 

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The T56 six speed manual used in f bodys vettes newer gto's and mustangs used atf. The t-5 in the fox body stangs, the 3550 used in 99 up stangs. From what I seen most newer manuals use atf. I have seen a few 90's chevy trucks that used motor oil.
 

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Just did a search on using ATF in a man-trans with wet clutch, Man this is more common then i thought , seems like the V-twin guys do it allot in the primary, may be something to look at.
 

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Does anyone know how similar the fiber material in our clutches are to the fiber material used automotive automatics? If it's similar or the same I'd feel safe trying atf in my trans.
 

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Discussion Starter · #18 ·
I just wanted to say, when I totaled my last unit, it was about a 45 mile drive to the dealership for them to confirm it was totaled. I drained the yamalube 15w50 and filled it with atf.

Running the 45 miles, it seemed fine. transmission was a little louder, but not as loud as with the original 10w40 fill.

It would have been interesting to pull the cover and look at the plates, but that wasn't an option.
 

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I am running Lucas semi syn 10w40. Weller Racing suggested it. I know they might be bias because they sponsor them. Running the Tubeworks clutch boss mod with Weller heavier pressure plate spring. Time will tell.
 
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