ShockerRacing

I just recently removed the Procharger from my 98 Corvette and there is a vacuum line coming from my FLT 4l60E Trans all the way up near the brake booster that is connected into the vacuum line on the brake booster right now. The connecter it is attached to is from Procharger and I intend on removing it as part of the supercharger kit and replacing the stock brake booster vacuum line. Where does this vacuum line from the 4l60e normally get vacuum from?

lucky131969

It doesn't normally, or more specifically....stock. They must have added a modulator, so you'll tee off vacuum from the same place, or any manifold vacuum source.

ShockerRacing

Thanks again for your help! It definitely doesn't look stock but I wasn't sure if it had just been upgraded.

lionelhutz

Where does it connect on the trans?

I'd be curious what was added to the trans which would require a vacuum source. The 4L60e trans doesn't need a vacuum source. The 700R4 didn't use a vacuum source either. So, there isn't factory parts or a factory location to put something that would use vacuum on that case. Maybe you should contact FLT and ask them about it.

lucky131969

This modification has been going on for 20+ years, since the 200R4 days...especially for those who wanted to install a late model trans, in a musclecar, streetrod, etc. Why they chose to do this on a street driven C5, is beyond me.

ShockerRacing

I bought the car with the upgraded trans already in it and I see from the receipt from FLP (they did the install) that they added a 1/4 inch steel vacuum line when they added the trans. the steel vacuum line goes from the trans along the torque tube and then up by the brake booster.

ShockerRacing

What was the purpose of the modulator?

Lionel, it comes out of the top of the trans on the passenger side.

lucky131969

It replaces the electronic portion responsible for pressure control in the trans. Supposedly, it results in faster downshifts, and better WOT shifting. Also, the line pressures are supposed to be sigificantly higher with a modulator.

Quicksilver Vert 01

The key word here is "supposed".

Since the 4L60E transmission is controlled by the PCM, line pressure can be raised to higher levels, if desired, by PCM tuning. A vacuum modulator is totally unesessary.

renegad44

And on a 4L60E, that tranny line pressure shoud be turned "on," correct?

Quicksilver Vert 01

I'm not sure what you mean by "should be turned on".

What I stated earlier, is that the transmission line pressure CAN be adjusted by modifying the PCM tuning.

It's not turning something on; just making a change to it.

renegad44

Thanks, I've heard some guys say make sure the line pressure is turned "on" and I'm thinking, to make adjustments to the PCM it has to be on. That may just be an off the wall term they are using. Of course mine is "on," my tuner just made adjustments after installing a new tranny.