Under the hood for the last couple weeks there has been a loud hissing sound. It turned out to be a vacuum hose had split and was all but falling off. I plugged it and the rpms raised a bit and the engine idled smoother and quieter. The hose that was split leads to this little ( I want to say pump) thing by the coolant resevoir and that leads to the TB cable for the transmission right?

I haven't gotten a chance to drive it after I did this as I had company over, but what does that vacuum line do for the tranny? I have noticed crappy shifting and wimpy performance. But only since the hissing started.

 

700R4s don't have a vacuum line going to them for anything.it sounds to me like you are talking about your cruise control valve. it has a cable going from the throttle body to a disc shaped object on the drivers side right behind the radiator. then, a vacuum hose that goes from there to a threeway vacuum fitting that also connects to the rear passenger side of the upper plenum. there is also a vacuum line that goes from the disc shaped abject to the brake pedal.

 

I don't know what it is, but as soon as I hooked it up, the performance came back, the idle went back up, and shifting improved.

 

performance came back and idle improved because you plugged a vacuum leak. the tranny shifted better because the engine was running better. the next time you drive your car with that vacuum line plugged, see if you have cruise control. i bet you don't. vacuum has nothing to do with the 700R4.

 

I know you're right. The way the hoses were routed in my engine, made it look like the hose went to that disk thing. No biggie. Car runs better, I'm happy.