Guys, I beleve I've killed my second C-6. It's now starting to slip in second and reverse... I'm hoping it isn't, but right now i think I over filled it. It was a quart low (or so I think, headlights don't let you see tranny fluid too well) so I added some. It's also been not shifting automatically, I've had to do it manually for the past month. I'm hoping a fluid flush and filter change will fix it, but we'll see. hey, that little 300 must be REALY stong to have kilt 2 of Ford's beefies trannys.

 

Transmission fluid is sometimes measured in pints, as in the dipstick might say it is a PINT low and someone might add a QUART by mistake. I had that problem with an Olds, my Ford is a manual shift.

Anyway, when a mechanic's helper added QUARTS to my Olds and it needed PINTS , I used a suction gun and a small rubber hose to draw out the extra fluid the way it went in.

I'm not sure if extra fluid would make it slip.

 

I over filled my transmission, and all it did was blow out the pan seal. Have you checked your vacuum modulator yet?

 

Are you sure the isn't over heating. if the trany fluid is brownish or darker than fresh fluid it might be over heating, try a aftermarket trany cooler put it on front of the radiator

 

Check the modulator on the transmission, and the vacuum line going to it. If it's not getting vacuum, or is defective, it will cause the problem you define.

Many times the rubber line at the modulator gets oil soaked, or dries out and comes off.