C6 no 3rd gear-'78 F150
 

I've searched the threads and read everything I've found so far. Still no help.

1978 F150 4x4 351M/400

I couldn't get the truck started over winter. When the weather warmed up I replaced plugs, coil, wires, cap, rotor, fuel filter, and a suspect fuel pump. That got her started up and running like normal.

Third gear has been working. 1-2 shift was sorta mushy and I poured some lucas oil tranny fix in it. About the same time I noticed the little clip on the carb had come loose that connected to the kick down. I went to get the clip and it popped off, did a somersault in the air, fell to the ground, and made it's permanent escape into the wilderness. So, I tied the kickdown in place with some wire.

I drove it to the gas station and noticed it was hanging in second. If I let off the gas it shifted into 3rd but as soon as any load was put on it it downshifted into second. A week later and now no 3rd gear. Tried manually shifting. Reverse seems weak. 1-2 shift was still mushy so I replaced the modulator which corrected the 1-2 shift. Still no 3rd gear.

I disconnected the kick down and have jiggled that up and down from the top and underneath. Nothing. So far that's all I've done. I haven't tried playing with the modulator or pin. I have never changed the fluid or dropped the pan. The tranny has always leaked a bit from the front seal but I just keep putting fluid in.

Any ideas on next step?

Take it out and rebuild it.

Well at least the clip did not hit you in the eye first.

1. Get a proper clip kick down clip.....JY?
2. Pull the vacuum line of the end of the trans modulator (with the truck NOT running) and see it there is any trans fluid in there, there should NOT be any.
3. See it there is any vacuum leaks.
4. Sounds like a fluid and filter change is in order.