C6 3rd gear Woes

[caddyman]

c6 tranny won't shift into 3rd... So here's the story. Went for a cruise a week ago, about 120 miles round trip, everything worked fine. It was warm out but not terribly hot, 80's. Car ran great! Even had an older fella, older than I, in his brand new top o the line corvette try to race me... ha. I wan't gonna bite on that. So we get back and I park the car. Week later the Fiance's car breaks the timing belt and I figure we'll take the mustang out for dinner on a nice cool evening. Starts great, backs out of the garage and down the street we go. Funny... stuck in first and wont shift to second. I try manually shifting to 2nd and she shifts. Then try shifting to third.... no go just revs up as if in nutral. Turn around and go home. Tranny is low, fluid at the fill line. Doesn't look brown or smell burnt. Should I just add some fluid? if so what kind? Not sure... From what I've read C6's took CJ fluid which is now compairable to mercon. I think its from a late 70's or early 80's truck but I'm not positive. Any suggestions? I am moving later this summer and am strapped for cash. If the tranny is shot I may as well just wait to put in T5 which would be way more fun for me. As always any help is greatly appreciated.

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[vescotech]

Check the hose to the modulator valve and make sure it hasn't come off. If its ok you may have a stuck govenor or stuck valve in the valvebody.

[caddyman]

What fluid does a c6 take?
No fluid came out of modulator but it is at the fill mark.
What next?

[plcdude]

I am thinking vacuum modulator. Before I replaced mine it would not shift to third either.