Vacume Modulator

[86C10]

I Have A 350 Turbo 3 Speed Tranny - It Isn't Shifting Out Of 1st Gear. I Was Told That It Was The Vacume Modulator. I Believe I Have Located It , But I Am Not Sure. It Has A Vacume Line That Connected To It That Starts By The Distributer Cap , And Winds Down To The Back Left Side Of Tranny Wich Is Where It Plugs Into The Vacume Modulator? I Think ??????
Could Someone Please Confirm This For Me - Please , And Or Tell Me If I Am Wrong.
Also - Does It Pull Out Or Screw Out Of Tranny ? Any Replies Would Be Greatly Apprreciated.

[ureckme]

Yes thats it. Theres a bolt and clamp I think that holds it on. I dont think thats whats wrong though.

[margie's71]

If I am not mistaken the modulator on a 350 should be ont the right (passenger )side of the transmission.It should be held in the transmission with one bolt 1/2"head and a bracket...need to make sure there is enough vaccum at the modulator end of the vacuun hose.If it is a solid vacuum hose, they have a tendancy to collapse from the heat and oil in that area.

[Zoomad75]

I don't think the modulator is why your trans won't come out of first. The TH350 I've got in my Nova had developed a leak in the modulator. This allowed engine vacuum suck ATF up the vacuum line and into the intake at cylinders #6 & #8. Massive clouds of white smoke under high vacuum (coasting) driving. During the entire time (I was on a 2 hour drive to get back to school) the trans shifted through all gears and performed relatively normal, except for the bug fogging smoke show.

The vacuum modulator does not control the shifting of gears from one to the next. It only aids in the timing of the shift and to a certain extent of the quaility of the shift. Stock modulators lack any adjustment, but there are aftermarket versions that you can adjust to adjust the quickness of the shift. The modulator would not prohibit the shifting from 1st gear.

I'd say you might have a problem in the valve body, possibly at the manual shift valve. Might be stuck in its bore. Might be time to drop the pan and take a look...

[LOHRTBT]

I had a similar problem with the cable detent up by the carb...that adjustment can mess up your whole day if its not adjusted properly.

[BIGCHEVYMAN]

chech the line first. the line should be steel but it will have a small peice of hose at each end for connection purposes. i have found many times the hose is collapsed or just unhooked.

[MylilBowTie]

How fast have you went to see if it would shift out of first gear? Have you checked the transmission fluid level and color? Its best to check it with the engine running so the it fills the torque convertor with fluid to get a better reading. While its running sit in the cab with your foot on the brake and run thur the gears R N D 2 1 and back up. That makes sure the valve body is full of transmission fluid. The rest of the transmission fluid that is in the pan is your reserve and that is what you need to check the level of.

It could be that your modulator valve is bad, the governor is stuck, or that the transmission needs overhauled. How long does it take to engage from park to reverse? That is usually the first common thing that starts to happen when its going out.

[86C10]

Thanks Everyone For Your Help And Input. I Installed A New Vacume Modulator Tonite , And It Does Shift Into Second Now , But It Does So Way Too Quickly. I Have'nt Gotten The Speed Up High Enough To See If , And When It Shifts Into 3rd.