Ford C6 Tranny Issue...

[HardcoreZ28]

Hey guys. I had a customer stop by today with his 69 Lincoln Continental with a trans problem. I believe it's the C6 tranny from the door tag. According to him he and a friend changed the points on it this past weekend as well as the vac modulator for the trans. He drove it home from his friends with no issues but when he went to use the car later that night it would no longer shift automatically. He can manually shift it still with no issues.
I swapped out the vac modulator tonight for another new one he had....the right one I believe. I think they put one from a C4 trans in it the other day...this was is supposedly the correct one for a C6. The line for the modulator goes up to the brake booster and the booster is definitely pulling vac. I then put a vac tester on the line and it's holding vac down to the modulator.
Any ideas what could be causing the sudden no shift condition? I checked the fluid and while it was a bit old it wasn't burnt and the level was correct.

[S.J.SLEEPER]

I believe the modulator has a set screw in the hole that the vac line goes to. should be a flathead. try turning in a couple turns then try backing out a couple turns if that doesn't help.

Also make sure vac line isn't melted on exhaust. i it is,,, this could give you good vac reading with a vac pump but indeed not giving vacuum to the mod. valve due to it melted shut.

[HardcoreZ28]

I'll have to try adjusting the set screw. The line should be good. Only the last few inches is rubber and away from the exhaust. The rest is steel.