Transmission fluid question.

2003 mustang gt modded · Mar 18, 2024

I did a lot of searching and seems like lots of mustang owners like to run atf in their t-5 transmission because it's thin and lubricates tiny bearing.

Is Pennzoil Syncromesh ok to use? It's supposed to be 5w-30 weight oil. Is it thin enough?

Why would so many people run Atf over Pennzoil Syncromesh. Isn't Syncromesh recommended.

Thanks.

revhead347 · Apr 5, 2024

ATF is what's recommended by Ford for the transmission. If you want to run something else, call Transmission Technology Corporation (parent company of Tremec) and ask. Everyone there is super helpful. I've had guys there go down to the engineering floor to actually look at parts for me and call me back. You will definitely get good advice from them.

Kurt

2003 mustang gt modded · Apr 7, 2024

Thanx for reply, I'm agreeing with atf. I just thought Syncromesh would improve shifting.

Since Ford recommendeds it, I'll be using mobil 1 synthetic atf.

Potomus Pete · Apr 7, 2024

I have been getting ready to do mine. I am going with Mikes 5L5 idea of Mobil One auto trans V/Ford product. From what I've been looking at that's the one for me

Mustang5L5 · Apr 25, 2024

IIRC, the only Tremec product that Syncromesh is recommended for is the TKO Line of transmissions. Perhaps even the original 3550 as well.

All others took whatever Dextron ATF was recommended at the time and have all been superceeded by Dextron/Merc V. It's tough to get an official tremec stance these days because they now offer their own line of trans fluid and have seemingly wiped all previous documentation as to what fluid to run and now say "run our fluid". (Tremec HP-MTF). Ford states Mercon V now.

I've run Mobil 1 ATF in mine since the early 2000's.

With that said. I know a lot of folks run SYnchromesh in a T5 and have not seen or heard of any instances of damage from it.

Food for thought..

https://www.corral.net/threads/t-5-fifth-gear-synchro-question.1377442/

WhiteCobra95 · Apr 28, 2024

When I bought my Cobra, everything was original factory, including the trans fluid. The T5 shifted okay, but it was unpleasantly notchy and didn't like finding first at a stop light when hot. When I tore it open to replace the 8-tooth speedometer drive gear with a 7-tooth gear for more ring and pinion choice options, I refilled it with Royal Purple MT fluid on a recommendation from a friend who uses it with heavy machinery transmissions. I also contacted Royal Purple directly to ask them if I should use their ATF or MT fluid for a T5. They said to use the MT fluid and that it already had friction modifier in it, so I didn't have to add any like you do for the factory recommended ATF. This was the first time I've used Royal purple for anything and I was skeptical, especially at the $17 / quart price tag at the time (it's probably way more expensive now). However, I was blown away by the difference. It's very noticeable. It feels so much smoother after switching. It's notchy, but in the good smooth notchy way you want from a muscle car manual transmission, and the resistance to find first gear when hot has completely gone away. I never would have believed that the fluid choice could make such a difference, but it does. Maybe my factory fluid was just old and warn out, but the improvement in shift quality / feel is completely worht the extra $$ in my experience.

limp · May 2, 2024

Tremec recommended Dexron III in my new TKX...
At the 500 mile fluid change, I might think about doing some synthetic ATF of some sort...
Things change, but Royal Purple had not been tested so it was not recommended...

Methodical · May 18, 2024

WhiteCobra95 said:
When I bought my Cobra, everything was original factory, including the trans fluid. The T5 shifted okay, but it was unpleasantly notchy and didn't like finding first at a stop light when hot. When I tore it open to replace the 8-tooth speedometer drive gear with a 7-tooth gear for more ring and pinion choice options, I refilled it with Royal Purple MT fluid on a recommendation from a friend who uses it with heavy machinery transmissions. I also contacted Royal Purple directly to ask them if I should use their ATF or MT fluid for a T5. They said to use the MT fluid and that it already had friction modifier in it, so I didn't have to add any like you do for the factory recommended ATF. This was the first time I've used Royal purple for anything and I was skeptical, especially at the $17 / quart price tag at the time (it's probably way more expensive now). However, I was blown away by the difference. It's very noticeable. It feels so much smoother after switching. It's notchy, but in the good smooth notchy way you want from a muscle car manual transmission, and the resistance to find first gear when hot has completely gone away. I never would have believed that the fluid choice could make such a difference, but it does. Maybe my factory fluid was just old and warn out, but the improvement in shift quality / feel is completely worht the extra $$ in my experience.

The issue could have been that the fluid in the car when purchased was old and never changed and any new fluid would make it seem better.

Transmission fluid question.

2003 mustang gt modded

Active Member

revhead347

Apparently my ex-husband made that mistake.

2003 mustang gt modded

Active Member

Potomus Pete

I'm still waiting for the fully nude shots

Mustang5L5

That is…until I whipped out my Bissell

WhiteCobra95

limp

wrap a little cheese around it and its a done

Methodical

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Transmission fluid question.

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Apparently my ex-husband made that mistake.

Active Member

I'm still waiting for the fully nude shots

That is…until I whipped out my Bissell

wrap a little cheese around it and its a done

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