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As my sig says, I have a shift kit on my C6 on my 1970 F-100. It always used to snap in the shifts, chirping the tires from first to second. I bought the truck from my brother, and he was the one that installed the shift kit. Unknowingly, as I was fixing it up, I found it was low on tranny fluid, so I added some Mercon to it, probably about 3 quarts. It ran like that for about a year. As I later came to find out, it needs Type-F. So I changed all the fluid out to Type-F, drained the converter and everything. The problem I've been having, is that in the past few months, and this started while the mixture was in there, that the shift from first to second is not nearly as crisp anymore, seems like a stock type shift, maybe even a little softer and slower. Any ideas as to what might have happened, and what I might have to replace? I'd say I'm a lot better with engines than transmissions...
Running Mercon in that transmission might cause soft shifts, but it's hard to say if 3 quarts would do it. And after changing back to Type F it should have gotten firmer, unless you wore out some clutches, but I couldnt tell you if only 3 quarts would do that. Kinda hard to say. How long did you have the mixture in there?
EDIT: I didnt see one year. But it's still hard to say what might have happenned.
Thanks for the reply. So, assuming it is worn out clutches, what would I need to do to fix it? Is it something that can be done while laying on my back under it, or does the tranny have to come out? If the tranny has to come out, I'll probably wait 'til I put the 390 in, and do it then.
Well if that was the problem then you would have to remove the transmission to replace the clutches. But I am by no means saying that is the problem! I really kind of doubt it and it's hard to say what the problem might be. The best advice I could give you is search around and ask some transmission shops. Maybe someone has had a similar problem.
The front band is used for second gear and could possibly do with an adjustment or you might find if the trans has a few years on it ,the servo piston might be getting a little hard and losing some pressure.....
Yeah I forgot about band adjustments. I am familiar with the newer electronic trannys and not so much with the old ones. I would def check adjustments. A Haynes manual will tell you how.