trany problem

[zuki]

i rebuilt the transmission in my rig, believed i had followed all the instructions correctly and kept everything really clean. it operates fine when cool, but when it gets warm, it slips when going into drive. when it does go into drive, it goes nice and solid. reverse works fine. it kinda acts like it is low on fluid, but it is not. trany is not overheating. fluid looks good, no metal shavings or anything in the fluid. any thougts on what i might have messed up would be appreated. it is a 1978 ford c4.

i checked the line pressure and in reverse it is about 75. nothing in any of the other gear ranges. the interesting thing is that it does move forward even though the pressure is reading 0. maybe i don't understand how things work in the trany but this is puzzling to me.

any thoughts would be appreated.

 

[Bruce]

If you are in the right pressure port and you only getting 75 psi in reverse you have a pressure regulator problem in the valve body OR you left the little pin out of the modulator that goes between the modulator and the little valve in the case. I would check for the pin first off.

 

[zuki]

so aparently i was in the wrong port. the picture in the haynes manual was actually of a c6 not a c4, anyway it confused me.

correct pressures are: and should be:
R 75 150-180
N 60 50-90
D 60 60-90
2 80 90-110
1 80 90-110

when it is slipping the pressures do not change.does not make any difference whether it is in D, 2, or 1. all acts the same.

it never slipps in reverse.

checked the pin in the modulator,and it is there.

 

[Bruce]

Sounds like to me you have a pressure regulator valve in valve body hanging up, sometimes the valve wears and causes it to hang and not stroke like it should . Another possibility is a bad pump ....Have you tried unhooking the modulator and see what your pressure goes up to?? another question..is it a new modulator i have seen these malfunction also.

Is the little valve that the pin sits in ..is it free and not hung up.??