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My C4 transmission was rebuilt at least once about 30 years ago, maybe later but I'm not sure. (I've owned it for a few years.) I have no idea what fluid is in it, maybe Type F, maybe Mercon of some flavor, maybe something else. It's an unknown.

I read that, if Type F is not available, to use Mercon V (a synthetic.)

I plan to drop the pan and replace the filter. I'm not pulling the trans so the torque converter will still be filled. When I add fluid after the filter change, should I add Mercon V?
 

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When in doubt use type F. Plenty of places sell it. If you know it has been rebuilt then Dexron/mercon 3 compatible fluid will work.
 

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Yes you can still buy type F and i think it shifts better with type F and if it still has the Ford converter you can drain it. Just remove the inspection plate you will see the flywheel turn the engine over by hand and you will see a drain plug.
 

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If the trans hasn't been rebuilt in the past 30 years, it most likely still has the type F fluid in it. I agree that type F is probably the best but if you have serious difficulty finding it you can use the Mercon. I'd try to add a quart of type F to the Mercon if possible. The Mercon alone won't give as crisp a shift as type F.
 

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Rule of thumb is that if it has ever been rebuilt then the original internal clutches that NEEDED Type F are long gone so you can now use Dexron III/Mercon. Some people use a quart of type F and fill the rest with Dexron III/Mercon, which is what I like to do.
Mercon V is a full synthetic and not really recommended for transmissions designed/made before the 1980's. To oversimplify, it's too "slippery".
 

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Want a really good fluid look for Transynd TES-295. I have been using it in all my c-4 transmissions for years with excellent results and it is a full synthetic dex/merc 3 compatible fluid.
 

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Discussion Starter #7
When in doubt use type F. Plenty of places sell it. If you know it has been rebuilt then Dexron/mercon 3 compatible fluid will work.
As I read it, you are an advocate for "Dexron/Mercon if you can't find F."

If the trans hasn't been rebuilt in the past 30 years, it most likely still has the type F fluid in it. I agree that type F is probably the best but if you have serious difficulty finding it you can use the Mercon. I'd try to add a quart of type F to the Mercon if possible. The Mercon alone won't give as crisp a shift as type F.
It HAS been rebuilt in the past thirty years...at least once, maybe more. I don't know the last time it was rebuilt only that it has been rebuilt (at least) once in its life and that was 30 years ago. (Hard to think that 1990 was thirty years ago! Feels like it was only 15!)

I think you share the same opinion as @cmefly : "Mercon if you can't get F."

Yes you can still buy type F and i think it shifts better with type F and if it still has the Ford converter you can drain it. Just remove the inspection plate you will see the flywheel turn the engine over by hand and you will see a drain plug.
I'm unfamiliar with this procedure, but I'm dang sure willing to give it a try. That's all there is to it? Rotate engine by hand (I'll use a wrench on the harmonic balancer) until a drain plug is viewable through a machined hole in the flywheel. Then remove the drain plug and allow to drain. How do I go about refilling so that I get fluid in the torque converter? I can just re-fill through the dripstick and it will get pumped into the torque converter? (This is important- I want to make sure I get it right.)

Thanks to all for your inputs.
 

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Discussion Starter #8
Rule of thumb is that if it has ever been rebuilt then the original internal clutches that NEEDED Type F are long gone so you can now use Dexron III/Mercon. Some people use a quart of type F and fill the rest with Dexron III/Mercon, which is what I like to do.
Mercon V is a full synthetic and not really recommended for transmissions designed/made before the 1980's. To oversimplify, it's too "slippery".
Thanks for your suggestion. I can follow that logic, makes sense. The source I read said to jump straight to Mercon V which seemed like a nuclear option. Dexron 3/Mercon seems more rational. Mucho appreciado.

I'll go with the Dexron and mark it down in the maintenance log for next reference.
 

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As I read it, you are an advocate for "Dexron/Mercon if you can't find F."



It HAS been rebuilt in the past thirty years...at least once, maybe more. I don't know the last time it was rebuilt only that it has been rebuilt (at least) once in its life and that was 30 years ago. (Hard to think that 1990 was thirty years ago! Feels like it was only 15!)

I think you share the same opinion as @cmefly : "Mercon if you can't get F."



I'm unfamiliar with this procedure, but I'm dang sure willing to give it a try. That's all there is to it? Rotate engine by hand (I'll use a wrench on the harmonic balancer) until a drain plug is viewable through a machined hole in the flywheel. Then remove the drain plug and allow to drain. How do I go about refilling so that I get fluid in the torque converter? I can just re-fill through the dripstick and it will get pumped into the torque converter? (This is important- I want to make sure I get it right.)

Thanks to all for your inputs.
If the converter has a drain plug and pretty much all stock style converters do, you will simply fill it back up from the dipstick. Add 4 or 5 quarts start the car run the car through the gears with foot on the brake then go to park with e brake on and check your fluid level while running and add as needed till full on the dipstick.
 

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My C4 was rebuilt last year. I used Dex/Merc III initially with but later dumped it (pan converter and all) and went with F because of the firmer shifts and it doubles as my power steering fluid. I’ve bought plenty of F at the two main auto stores around VA and MD Advance + Auto Zone. So F is still carried and not going away anytime soon. But as GypsyR said modern clutch materials no longer will fry if using something other then the type F.

You can and should drain the converter. Many have a drain plug. Just need to take off the flexplate cover + rotate from the crank pulley until you see it. There is a slightly larger hole between 2 of the 4 converter bolts that will have a drain plug bolt protruding out of the flexplate.
 

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If you really want to run synthetic, B&M sells a blue fluid called "Trick Shift". Nobody around here carries it, I have to order it from Summit Racing or Jeg's. It's the best replacement fluid in old Ford transmissions that originally used F. Also is the business for T5 manual transmissions. Kind of overkill but really good stuff. Seriously. Even though I don't really care for anything else B&M puts their name on.

Standard fill procedure if you've drained the pan AND the converter is to fill with four quarts, crank it up, and then IMMEDIATELY add another four quarts. Total capacity "dry" is usually 10-14 quarts. You never can drain it all without a complete teardown. How much is left varies a bit with how long you drained it. You want to add the extra four quarts ASAP because the pump can just about evacuate what's in the pan by the time you walk from the ignition switch back around to your fluid and funnel. On some vehicles you can even hear the pump whining a bit when it's sucked up all the fluid and is running dry. Not a really big deal on our old stuff but some late model stuff has to be overfilled some before you crank the engine because they pump it out so fast. (Specifically the Ford 6R140 for example). It's generally not good for any pump to be run dry. Now if you just changed the fluid and filter you can just add two quarts, crank it up and start checking the dipstick, no big rush when the converter is full. On a newly rebuilt transmission it's important to run the car in the different gears or at least put the shifter through all the positions to make sure all the drums are charged with fluid. These will not be drained during a simple fluid change. You do need to drive the car until the wet end of the dipstick is uncomfortably hot on your fingers. Then recheck the level. Don't worry with the cold level too much, as long as there is some fluid on the stick, it's that Hot level you are shooting for.

The main reason to change fluid is to refresh the additive package. If that's what you want, then you can just drain the pan and not worry about the filter. That's why just draining the pan has been standard fluid change procedure on most transmissions for years and years. I'm not a fan of transmission (wallet) flushes. When you have no idea of the transmission's history, changing ALL the fluid is the safe choice. But if it has been in your care for a while and you've changed the fluid at some point before I would recommend just doing a pan and filter. Skip draining the converter. If you see a lot of black or chunks of things in the pan, don't change anything. You've got issues that fresh fluid won't help.
 

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If you really want to run synthetic, B&M sells a blue fluid called "Trick Shift". Nobody around here carries it, I have to order it from Summit Racing or Jeg's. It's the best replacement fluid in old Ford transmissions that originally used F. Also is the business for T5 manual transmissions. Kind of overkill but really good stuff. Seriously. Even though I don't really care for anything else B&M puts their name on.

Standard fill procedure if you've drained the pan AND the converter is to fill with four quarts, crank it up, and then IMMEDIATELY add another four quarts. Total capacity "dry" is usually 10-14 quarts. You never can drain it all without a complete teardown. How much is left varies a bit with how long you drained it. You want to add the extra four quarts ASAP because the pump can just about evacuate what's in the pan by the time you walk from the ignition switch back around to your fluid and funnel. On some vehicles you can even hear the pump whining a bit when it's sucked up all the fluid and is running dry. Not a really big deal on our old stuff but some late model stuff has to be overfilled some before you crank the engine because they pump it out so fast. (Specifically the Ford 6R140 for example). It's generally not good for any pump to be run dry. Now if you just changed the fluid and filter you can just add two quarts, crank it up and start checking the dipstick, no big rush when the converter is full. On a newly rebuilt transmission it's important to run the car in the different gears or at least put the shifter through all the positions to make sure all the drums are charged with fluid. These will not be drained during a simple fluid change. You do need to drive the car until the wet end of the dipstick is uncomfortably hot on your fingers. Then recheck the level. Don't worry with the cold level too much, as long as there is some fluid on the stick, it's that Hot level you are shooting for.

The main reason to change fluid is to refresh the additive package. If that's what you want, then you can just drain the pan and not worry about the filter. That's why just draining the pan has been standard fluid change procedure on most transmissions for years and years. I'm not a fan of transmission (wallet) flushes. When you have no idea of the transmission's history, changing ALL the fluid is the safe choice. But if it has been in your care for a while and you've changed the fluid at some point before I would recommend just doing a pan and filter. Skip draining the converter. If you see a lot of black or chunks of things in the pan, don't change anything. You've got issues that fresh fluid won't help.
Gypsy, I’ve found today after reinstalling my C4 on my 68’ C4 that it’s pan ONLY holds about 2.5 Qts. This is with a slightly deeper aftermarket pan with a drain plug. I measured the pan drain by refilling empty bottles. The converter + pan emptied I got about 7 or 8 in there total. I’m guessing that more sits in the case and drums? When in run it’s again in a couple days I’ll bet I’ll need to top off. Engine was hot during the 2nd half of the fill.
 

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Discussion Starter #13
If you really want to ...
...a pan and filter. Skip draining the converter. If you see a lot of black or chunks of things in the pan, don't change anything. You've got issues that fresh fluid won't help.
Dang if I could "double-like" a post, this one would get it. Thanks for the excellent guidance!
 

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you can still get Type F right from Ford. price was $47 for a case last year when I did my PS and tranny flush
theyll have to order it so you might get the counter guy a bit upset. They got it for me in 2 days

Dont use the El Cheapo Walmart Type F

my local Advance and Pep boys still carry Valvoline but for the same price i got motocraft
 
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