late 3-4 upshift

[sunfish32]

i have a 1986 300e with a 722.3 transmission. I have a fairly good upshift from second to third but i seem to have a very late upshift to fourth like it won't happen until 3500+ rpm. Just recently i replaced the vacuum modulator and the new modulator holds vaccuum and receives good manifold vacuum. I have made some cable adjustments which helped to bring the 2-3 upshift back into the proper range but they did not seem to affect the 3-4. does anyone know of a good printed or electronic transmission manual that could help me troubleshoot this tranny? i have the microfiche but they are unbearable to work with and very hard to read. the transmission shifts firmly into third but late into fourth but i get a good shift when finally occurs
HELP
MIKE