T45 builders recommend Merc V but I put in Merc III (good results)

DVJ38

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So whenever I read a thread or post about build T45's or atleast rebuilt ones from all kinds of different builders (The T45 Source, Hanlon, Astro, etc.) they all recommend Mercon 5. It's funny because stock our cars take Merc 3. Now I was thinking maybe they are recommending the more slippery stuff since they are using carbon fiber lined synchro's. Some people say run whatever the builder recommends, others say that our transmissions were designed for Merc III so use that. I used Merc V since that is what my builder recommended. I had that in there for 6,000 miles or so. Lately the shifting hasn't felt as good so I figured I'd drain the fluid and see what it looked like, and just put some fresh stuff in. My old fluid was already fairly dark and has lots of tiny shiny pieces in it. Granted that is with lots and lots of redline shifts and not being easy on the car at all though. I ended up trying out the Mercon III and it feels much better than it ever did with the Mercon V! So I'm going to run Mercon III for about the same mileage and drain the fluid to see what it looks like. I know that it definitely feels better to shift though.

So I was wondering if anyone else has tried Merc III instead of Merc V and what your findings were. Also, I would encourage people with Merc V to switch to Merc III in their aftermarket built transmissions and report the results.
 

CJK440

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I use type f. Type f was the performance atf for automatics because it was supposed to let the clutches grab harder than dex or merc, I figure the same principle with a fiber syncro too. Works like a charm.

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98$vt

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Good to know I just put a new t45 in my car with merc 5 I'll try out 3 and see if I notice the difference
 

STAMPEDE3

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I use type f. Type f was the performance atf for automatics because it was supposed to let the clutches grab harder than dex or merc, I figure the same principle with a fiber syncro too. Works like a charm.

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Type F was used long before Dex and Merc, not because it grabbed harder but because those were not even out yet it really wasn't considered performance.
Ford used F in all vehicles back then and everyone else used ATF.

F was in the 70s and before and hasn't been used in years other than for power steering in 95 and older.

Some tractors use it for hydraulic fluid too.
 

CJK440

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Type F was used long before Dex and Merc, not because it grabbed harder but because those were not even out yet it really wasn't considered performance.
Ford used F in all vehicles back then and everyone else used ATF.

F was in the 70s and before and hasn't been used in years other than for power steering in 95 and older.

Some tractors use it for hydraulic fluid too.

Of course. But I believe the new fluids have different friction modifiers to allow for smoother passenger car shifts. The old tech type f lacks these advancements and supposedly makes for a grabbier clutch apply.

Many performance automatic builders recommend f, at least in vintage non electronic trannies.

For a while the rumor was that b&m trick shift was just blue type f.

The stuff stinks though.

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DVJ38

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I use type f. Type f was the performance atf for automatics because it was supposed to let the clutches grab harder than dex or merc, I figure the same principle with a fiber syncro too. Works like a charm.

Sent from my Vortex using Tapatalk 2

I always hear you say you use type F but I'm too much of a wuss to try it. Maybe down the line though lol

Good to know I just put a new t45 in my car with merc 5 I'll try out 3 and see if I notice the difference

Please let us know what you find.

this just reminds me I have not changed the fluid in my trans in like 5 years.

haha wow

fwiw I just did this last week, went from merc 3 to 5. I don't notice much one way or the other.

Good to know, thanks for the input.
 

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