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In the diagram above, it shows the vacuum connection for the modulator coming off at about the 2 o'clock position. My modulator vacuum connection comes straight out.
This would seem to indicate that I have an aftermarket generic modulator. If that is the case, I have two choices. Either A) Use a 90 deg elbow to connect the vacuum tube, or B) get the correct modulator.
Edit:. After looking for a replacement modulator, it appears that they all have the connection pointing straight out like mine. Looks like I'll be using an elbow.
Referencing the photograph:
1) The replacement vacuum modulator is normally supplied with a rubber 90° elbow hose. The vacuum modulator shown in the photograph is a replacement.
2) The connection to the vacuum modulator shown in the photograph is problematic. Get rid of the rubber line and hose clamp.
3) RTV on transmission pan gaskets. If the shifting problem isn't the connection to the vacuum modulator or the vacuum modulator itself then the next avenue of exploration is for stray bits of RTV.
4) Transmission cooling lines should be metal.
5) What the heck is going on with the zip tie?
The vacuum modulator line doesn't need a hose clamp. Try to gently coerce (bend) the metal line so you have a better lining up of the modulator and metal line. Use a fresh piece of rubber vac line and you should be good, make sure the routing is clear of the exhaust pipe. As mentioned earlier the vacuum source needs to be a direct source. Which I think you have done already.
Referencing the photograph:
1) The replacement vacuum modulator is normally supplied with a rubber 90° elbow hose. The vacuum modulator shown in the photograph is a replacement.
2) The connection to the vacuum modulator shown in the photograph is problematic. Get rid of the rubber line and hose clamp.
3) RTV on transmission pan gaskets. If the shifting problem isn't the connection to the vacuum modulator or the vacuum modulator itself then the next avenue of exploration is for stray bits of RTV.
4) Transmission cooling lines should be metal.
5) What the heck is going on with the zip tie?
1. The modulator was on the car when I bought it, so the 90 deg elbow was non existent.
2. I got rid of the rubber hose and clamp and installed the correct line yesterday along with a 90 deg elbow.
3. I'll keep thr RTV issue in mind.
4. Why do cooler lines need to be metal? I've had the rubber hoses on for over a year now and they've been fine. Plus, I'm not using the cooler in the radiator, I have an external cooler.
5. Not sure about the zip tie...but it's out of sight, out of mind, and it's not hurting anything, so I'm OK with it.
the loop is to prevent condensation from forming and running down into the modulator.
If tge vehicle is used for several short trips and enough condensation collects in the modulator, and then the condensation freezes it can lock the modulator valve solid. Now imagine starting a cold engine on fast idle, with cold atf, and putting the transmission in reverse. If the valve is immobilized, instead of the expected 250-280 psi of line pressure, it can go to 700-800 psi. If you’re lucky, it will break the band or crack the servo piston. If your unlucky, it will break the case.
Another example of GM not doing unnecessary processes or steps.
