Manual trans fluid.
Senior User
Joined: Jul 2010
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From: Sullivan, MO
Anything that meets the Mercon spec should work fine for you. The license on the name "Mercon" ran out a few years ago, so companies don't have to put it on the front of the bottle anymore; however, there should be a list of specs on the back of the bottle. I know the 5 and 6 speeds behind the diesels recommend a synthetic version of Mercon, so that may be something to consider, too. Personally, I would try to stay as close to the recommended fluid as possible, either the conventional or synthetic version. Sometimes the "one fluid for all cars" trans fluid can backfire on you, even if it meets the Mercon specs. Hope this helps.
Post Fiend
Joined: Jun 2001
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From: Running Springs CA
I'd go with Redline D4 ATF, because its API GL-4 as well as Mercon and Mercon V. "Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)"
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Elder User
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Thanks for the replies! I thought it would be interesting to note that my trans has some wear. You have to be at very low speed or stopped to go into second (I take off from a stop in second). Sometimes it will grind a little when I turn at low speed trying to get it into second. This is a grey area because a lot of the times I am not moving fast enough to use 3rd gear in some turns. Any additives? Certain brands? Lucas? Royal purple? I am thinking ill probably just go with the motorcraft but I'm hoping like heck there is something better for my tranny with some wear.
Post Fiend
Joined: Jun 2001
Posts: 5,228
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From: Running Springs CA
The grinding usually means synchro wear. The last thing you want is a more "slippery" fluid, which is what many additives do, just making it worse. A trick I have used in the past in this situation is find some Type F or FA ATF. It has no friction modifiers, like Mercon/Dexron, so the synchros can "hook up" a little easier.
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Elder User
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Ok guys, I got 4 qrts of motorcraft mercon v. Put it in. Gears want to grind a little bit worse now. I am going to try to put some Lucas trans additive in. Says it helps with wore manual transmissions. Anyone ever used this stuff? Will this make the fluid more slippery?
Lucas Transmission Fix : Lucas Oil
Lucas Transmission Fix : Lucas Oil
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Post Fiend
Joined: Jun 2001
Posts: 5,228
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From: Running Springs CA
Dont do it. That stuff is for automatic transmissions. Get some Type F ATF. The Mercon V was the wrong direction to go because it has more friction modifier than the old Mercon. Manual transmissions work totally different than automatics. MT synchros are all metal, AT clutches are faced with organic materials. ONLY Ford still recommends ATF in sticks, I think just so the dealers dont have to stock too many different fluids for the small number of MT's sold today. GM and Chrysler use synchromesh fluids especially for manual transmissions. You could also try that. The Pennzoil synchromesh fluid is stocked by just about every FLAPS.
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Elder User
Joined: Jun 2011
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Dont do it. That stuff is for automatic transmissions. Get some Type F ATF. The Mercon V was the wrong direction to go because it has more friction modifier than the old Mercon. Manual transmissions work totally different than automatics. MT synchros are all metal, AT clutches are faced with organic materials. ONLY Ford still recommends ATF in sticks, I think just so the dealers dont have to stock too many different fluids for the small number of MT's sold today. GM and Chrysler use synchromesh fluids especially for manual transmissions. You could also try that. The Pennzoil synchromesh fluid is stocked by just about every FLAPS.
Post Fiend
Joined: Jun 2001
Posts: 5,228
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From: Running Springs CA
In an older trans that already has worn synchros, Type F would be my first choice. Is cheap and should be relatively to find. Sychromesh fluid would be second, slightly thicker (9.1cSt @ 100C vs 7.3) than ATF, but formulated specifically for manual transmissions. D4 is expensive and may not be best for an already worn transmission.
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Elder User
Joined: Jun 2011
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In an older trans that already has worn synchros, Type F would be my first choice. Is cheap and should be relatively to find. Sychromesh fluid would be second, slightly thicker (9.1cSt @ 100C vs 7.3) than ATF, but formulated specifically for manual transmissions. D4 is expensive and may not be best for an already worn transmission.
Elder User
Joined: Aug 2012
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I will be trying PZ syncromesh, I have had Amsoil syn ATF in for about 500 miles so far, and I think its just too slippery for proper syncro engagement.
The nice thing about syncromesh fluids and MTF's (manual trans fluids) is they offer a similar viscosity to ATF but with much more anti-wear additives and a proper coefficient of friction for syncro operation.
They are more of a "best protection" fluid instead of a "What is easiest to stock" fluid.
The nice thing about syncromesh fluids and MTF's (manual trans fluids) is they offer a similar viscosity to ATF but with much more anti-wear additives and a proper coefficient of friction for syncro operation.
They are more of a "best protection" fluid instead of a "What is easiest to stock" fluid.