How to check and fill FMX transmission

Hey guys.

I know the information I need is already out there but google searching has brought me conflicting information, so I thought I'd ask the collective wisdom of the board.

I have a 1971 mach 351 Cleveland with an FMX transmission. The trans is of course leaking small drips onto the garage floor which 2 mechanics now can't seem to fix and I have resigned myself to living with it The question I have is:

What is considered the best procedure for checking the transmission fluid level? Car up to temp and running in Park? Different people seem to say different things.

And I'm cringing to ask this in public, but do I add trans fluid to the tube the dipstick comes out of?

Please educate me.

Thanks guys.

Yes, add ATF into the dipstick tube. Engine should be at operating temp. Check on level ground.

The trans can be leaking from one of five places:

The pan gasket, dipstick tube seal or modulator seal...all easy to fix.

The tailshaft or cooler lines are only slightly more difficult to fix. Any decent mechanic should be able to find and fix quickly.

Other potential leak locations, the shifter shaft seal and the input shaft/torque converter seal, not easy fixes.

You have to take the transmission temperature into consideration when checking it. Check the fluid level with the engine running and transmission in park. If the transmission fluid is cold, the fluid level should be at about the add line on the dipstick, if warm it should be between the add and full lines. The only time it should be at the full line is when the fluid is hot.

Other potential leak locations, the shifter shaft seal and the input shaft/torque converter seal, not easy fixes.

You have to take the transmission temperature into consideration when checking it. Check the fluid level with the engine running and transmission in park. If the transmission fluid is cold, the fluid level should be at about the add line on the dipstick, if warm it should be between the add and full lines. The only time it should be at the full line is when the fluid is hot.

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Thanks guys. That's what I needed. This forum is a great resource. I will check and top it off as soon as it warms up a bit.

I started with a pan gasket leak and I've had a couple different mechanics try to seal it/get it to be flat and the pan may be fixed now but the transmission is still leaking. I've got another mechanic I might try. There doesn't seem to be a lot of parts support for FMX transmissions.