79 C6 Transmission fluid Question
 

Hello Everyone,

I know this question has been asked before but wanted to get your opinion. I have a 1979 ford f 150 with a c6 tranny. I changed out the filter and gasket yesterday but now wondering which type of fluid I should add and how much. Its too late to drain the converter and I dont think I could do it even if I wanted to. So, do I use type F or Dextron111/Mercon? The dipstick calls for dextron but I have heard many people use type F on their 79 trannys. The truck was given to me and the older lady that owned it before me does not know who rebuilt the tranny many years ago because her husband took care of it and he past away 4 years ago. What do you smart gentlemen think I should do? My gut feeking says go with dextron but I do not want to mess it up. By the way, the manual also calls for dextron on models 77 and up. Thanks in advance!

You should be able to drain the converter if it's a stock one and even some after market ones. Take the dust cover off and the drain plug should be in between two of the converter nuts.

You can use either one and it won't hurt it. I run type F in all of mine now.

Thanks guys for the input, if I remove the dust cover I believe I will have to also remove the flywheel correct? Do I need to seperate the tranny in order to drain the converter? Also, Ranger 429 the problem is I do not want to mix the fluids up. I do not know whats in the tranny now (converter) so I am afraid to mix up type f with mercon or vise versa. I might get lucky if I guess it right but wanted to ask around before I do it. Thanks

No need to remove anything. There is a drain plug.

Ok hillbilly Deluxe81, I am new to all this but want to learn. The dust plate is the plate that is between the tranny and oil pan correct? Also, I would have to remove the starter before I remove the plate right? After removing the plate, you say there is a plug to drain the tranny fluid. Is the plug visible thru the flywheel? Man, if its that easy I think I am better off draining the converter then going with dextron fluid. Thanks

Yep, it's that easy. And No you don't have to remove the starter.

If the trany is a 79 for sure , I would use type dexron III mercon, not type F A , I just checked on that for my vehicals. My 66 uses type FA and the 79 uses dexron III mercon . After all , why would you want to put something in your transmission if FOMOCO says use the correct one, There can't be any cost savings.

C6 as original: 1966/76 = Type F // 1977/96 = MERCON

Type F will shift firmer and help the tranny last longer.

Josh

:D Do you have any engineering proof of that? If "NumberDummy " agrees with you I will go along with it . :-X0A6

haha any engineering proof. From my limited knowlege and exp. i would agree with Bullitt390. Pretty sure they are mixable(I've done it with no adverse affects) aswell as Type F has " F"riction additive. best i know is that it'll grab better but with more grab.. sometimes can come more wear. really cost wise won't be much different, and once an a while its out of stock at my parts store but its very easy to get more.
my2cents

Actually, it is the Mercon that has more friction modifier. "Friction additives" don't increase friction, they reduce it. The same thing applies to the friction modifier that you add to limited slip differentials. The addative does not help the clutches "grip better". It actually helps them slip more.

That being said, USE THE CORRECT FLUID. Don't compromise your transmission with some second hand knowelge. Especially when it is incorrect.......

A Brief history...

Dexron was released in 1972, previously they used Type A. Dexron was developed to create SOFTER shifts in their higher in models i.e. Buick, Oldsmobile, Pontiac and Cadillac.

Ford continued Type F for the firmer shifts until 1977 when they too jumped on the "less bang" shifting.

As for engineering, I highly doubt B&M Trick Shift, Hurst HOT shift, and others which are just TYPE F would be marketed to racers and towing if it didn't work.

Others will say Mercon was the spec fluid because of the material of the bands. It was the spec to create softer shifting so grandma or some flamer wouldn't test drive a Ford and then test drive a Chevy and be "Gee this Chevy sure is smooth..."

Those in the know, know otherwise.

Josh

Yes , ha ha ha , 2 cents, thats about what it's worth to me. I believe FOMOCO got some engineering done on the mix before using it . I don't believe they just mixed up some stuff and said " that looks o.k. ,lets use it . ha ha .