Truck: 1978 Ford F250

Hey guys, hoping for a bit of advice for this nooby.

I inherited this truck and sadly it's dripping transmission fluid onto the exhaust. I checked the fluid and it's a little on the low side.

So what I want to do before driving it around again, in order to make it leak in hopes I can see where it's coming from, is top off the fluid.

According to my Haynes book it says that I should use "Dexron III or Mercon automatic transmission fluid."

Reading around it seems that Dexron was made for GMC and Mercon was developed by Ford. I'm looking at the website for the autostore and it looks like Mercon V is all that is available.

I also am not comfortable assuming that the fluid I have in the transmission is Mercon. So I'm concerned that I may mix fluid types and cause problems.

Any advice would be great. Thanks in advance.


-Paul

 

C4 (1964/76) & C6 (1966/76): TYPE F ATF / 1977 and later C4/C6 = MERCON aka Dexron II (as it was called in the 1970's).

You sure your 1978 F250 4WD has a C4? If it does, it has a 300 I-6, but 1978 was the first year that 300's were available with the C6 in F100/350's.

 

Ya, I made a mistake. Meant to put C6. It's V8, 460.

 

The 460 was swapped in, 460 not available with 4WD (and M/T) until 1983 and then in F250/350's only.

 

OK.

Have any advice about my question though?

 

I already listed the types of ATF and when they were used.

 

Wonder if that '78 C-6 has ever been rebuilt?

I offer this from an industry paper on transmission fluids.
See if that number is on your dipstick. The Type CJ and the later Type H are no longer available and replaced by Mercon. Any trans that has Type CJ (looks yellowish) in it can use Mercon, Mercon V, or DexIII/Mercon.

If it was rebuilt, likely it has already been filled with Mercon at least.

More reading : Martin Lubricants Technical Service Bulletin ? Transmission Fluid Guide

 

ESP-M2C138-CJ is what's on the dipstick. It's a reddish fluid though, not yellowish.

Is the Mercon a clear/red?

 

Type F ATF is red. Mercon is a different color, but what color it is, I cannot recall.

 

At the store they're selling Dex/Merc type in STP and Castrol.

It's also red in color. Pretty sure I have the right stuff.