68birdls1

iTrader: (46)

hey there, i did a search and it didnt help me at all! but i have installed the 4l60e in my 68 firebird and i have noticed that it has a vaccum line on it with a "t" like thing in the middle. one end goes inside the tranny, the other just dumps out to the side and there is an openin on the "t" thing that i dont know what goes there if any?!? are there supposed to be any vaccum lines on the tranny and if so what all do they hook up to?!? thanks in advance

daniel

WILWAXU

iTrader: (6)

Needs a vacuum source.

On the late model cars, we T into the brake booster line.

68birdls1

iTrader: (46)

ok thats what i was wondering, i was pretty sure that i needed it! but one end of my vaccum line just drops out into nowhere! i dont know if it came off of something or what?!? do you know what both ends of the line are supposed to be hooked up to?!? and could i T this vaccum line into the lines that go from the manifold to the valve covers because i have manual brakes with no booster thanks for the quick response and i look forward to your next one!

daniel

1QUIKWS6

iTrader: (61)

Apparently you have a vacuum modulated 4L60E (which is preferable over the electronically controlled units) - the vacuum line you speak of needs to be connected to a full time vacuum source.

The modulator reads the vacuum level of the engine (hence the load) and adjusts the line pressure in the tranny accordingly (hi vacuum - light load=low pressure & low vacuum - heavy load=high pressure). You should NOT run the car with this line disconnected. The tranny will not be able to raise the line pressure as needed and the clutches will slip drastically - eventually burning them up.

According to Dave @ Rock-On transmissions - a lag of only a second or less in response time of the line pressure will cause the clutches to slip.

68birdls1

iTrader: (46)

thanks man! i was jsut talkin with john from speartech and he said that it is just a breather hose! not a vaccum modulated 4l60e, just a breather hose. but thanks for all the help guys!

daniel

WILWAXU

iTrader: (6)

Time out.

Where is the nipple located?

If it's coming off the top of the tranny.. it's a vent line, not vacuum.

The vacuum line for a modulator normally comes off the top of the valve body, near the plug connector for the computer. Normally it's a small brass fitting.

WILWAXU

iTrader: (6)

Ahh.. good catch

1QUIKWS6

iTrader: (61)

Since this is in a 68 Firebird - are you using a standalone controller for the line pressure, shift points, etc.?

Cause if you're not - then it has to be vacuum modulated.

Unless of course you swapped the entire PCM/wiring harness for the engine - assuming this a LS1 transplant?

68birdls1

iTrader: (46)

yes sir it is a transplant, everything out of a 99 ta is in the car. i have already had the wiring harness reworked by speedtech and sometime this week i will start pluggin everything up! but thanks for checkin up

daniel