Hot Rods Ford C4 Trans., no reverse

Need help with a Ford C4 trans., metal tag # E1SP EA, brass tag on valve body # D104. Appears to be one of the final years made.
Have no reverse. Was rebuilt 7 yrs. ago, sat dry in project car during this time. Finally got the project started up, trans fluid added & trimmed out at 180 degrees, drive works, but no reverse.
What has been done:
- Adjusted reverse band per spec.
- Changed reverse sevo.
- Removed valve body to inspect for the two check balls & hockey puck, all present. Replaced valve body gasket.
- Check operating pressures, with the modulator vac line connected found 60# in park & drive, 90# in reverse, which is low from the spec of 175#.
- Removed vac line from modulator, had 150# in park & drive, 75# in reverse.
It appears the pump isn't up to spec. or the fluid is bypassing / being diverted incorrectly.
Certainly would appreciate the HAMB's help on this.
PM or post your reply.
Thank you, Zeke

 

Does the transmission shift up and into 3rd gear while in D range? If not, then the reverse/high clutch seals could be leaking.

 

75 psi in reverse points to a fluid leak in the reverse hydraulic system not a pump problem since you have good pressure in P and D. With the vacuum line off the modulator, reverse pressure should be about 190 psi. If you drop the valve body, you can test the servo by applying air pressure to the rear servo apply port just below the rear servo. If the servo works with air pressure, the problem has to be valve body related. I do not have a hydraulic diagram for the late C4's. They did make changes to the valve body in the mid 70's and the latest diagram I have is 1970. If you have the correct hydraulic diagram you can trace the rear servo circuit to see where in the valve body you may be dumping pressure.

 

My Dad and I went through a C-4 five times trying to find the issue with his; it was the seal around the clutch band servo with a fine split in it. It would shift into gear and then fade out. I had a similar failure on one of my Falcons and was so ignorant about transmissions I didn't even try to fix it. Today? I'd clear off the kitchen table and rebuild it right there between bites of dinner....