i bought a 78 F150 two years ago and after fixing some stuff i started to drive it. It has a long delay into reverse so i dropped the pan to change the filter and fluid. It was dirty but not burnt or smelly. I installed a new filter and installed the pan, filled up the pan then i removed the return line from the trans cooler and stuck it into a gallon milk jug. Had my cousin start the truck no fluid? So i bought a can of trans flush and sprayed it into the feed cooler line then took my compressor and blew out peanut butter! I did this three more times until it came out clean, i then installed the feed line had my cousin start the truck and i got clean fluid out of the return cooler line finally! I pumped 15quarts through the trans installed the lines and checked the fluid level and i drove the truck. It still has a long delay in reverse and now when you put it into reverse you feel it go in gear then you push the pedal and the trans slips in reveres then gets a light bang and moves back wards? Problem is it only does this when it hot like after playing around off road driving up and down hills etc. No mud yet the motor is tired and the factory gears cant turn the 33x12.50's i have good. Does the trans need to be rebuilt also with the motor?

 

hmm to be honest if your rebuilding the engine it wouldn't hurt to do the same to the tranny. I had this done not long ago and wow was I happy with the results. If the tranny only performs bad when the engine gets hot, either the tranny lines aren't cooling it correctly or the engine isn't working properly with the torque converter. Those are my best opinions. I'm sure others on here can help more as well.

 

i just ripped the motor down to a short block, nothing but crank and pistons left in her. Everything was shot! cam was ground and burnt, lifters gunked with sludge, o did i mention sludge like peanut butter everywhere inside! Im calling some shops monday to get a price on steam cleaning, new cam bearings installed and having the crank and cylinders checked so i can rebuild the old girl. I suppose now ill have to start saving up for a master rebuild kit for the trans and ill rip that apart too.

 

Odds are you still have peanut butter still in the C6 valve body. Time for a rebuild. It isn't that hard to do.

 

It seems like a trait with the C4 and C6 when they get a little age on them. I think the seals get worn and start to leak pressure until they heat up a bit and expand enough to seal.
I just got a 78 with a C6 and you have to make "reservations" with it when you first put it in gear. Once it gets rolling it's fine. I'll be pulling it in the near future to freshen it up.
The C4 in my 79 only does it when it's 15* outside and you first put in gear, othewise, it's fine.

 

yea its funny how only in reverse it does it but other than that the transmission is fine. It shifts perfect maybe a little too fast but i think i can change the weight to make it shift later in gear correct? I guess now ill have to rip the trans apart after i get the motor finished up. Theres another month or two i wont be driving my old girl

 

Sounds like you need a manual trans set up and engine ...from the guy who bought the bronco parts from you on the EAST side of NJ.....funny thing is my bronco only hesitates in fwd when it is cold, then it is fine..is this the truck you were building when I was out there to pick up the parts?

 

After you rebuild it, I would make sure to adjust the kickdown rod to spec and maybe get an adjustable modulator. I would only change the weight after the kickdown and modulator have been fine tuned. When you tear the trans apart, make sure the gov spring isn't broken or weak.