Testing a Vacume Modulator on a TH 350

[VanceH]

Is there a way to test this and see if it is working? After removing my front drive shaft on my 4x4 i am having issues with the tranny. It is shifting WAY late into 3rd and i have no down shift at all, you let off the gas and it feels like it is free wheeling. I was running it around last night and came down a hill and it shifted, was ok for a bit then went back to no down shift. from the research i found i am thinking it might be the Vacuum modulator?

[Myself]

Pull off the modulator and find a piece of tubing to put on it. Long enough you can face the modulator towards you and watch the inside movement. Suck on the tubing until it pulls in then stick your tongue over the tubing. The modulator should stay pulled in. If it pushes back out while your blocking the tubing with your tongue, then the diaphragm is bad.

[Wrenchbender Ret]

If there is any sign of fluid when you remove the vacuum hose it definitly is bad.