The guy who had my TA before me said the trans is built and can handle 500+ horsepower. I just nodded my head cus i never believe anything a seller says but whatever. So as im checking out my engine bay i notice my brake booster hose is T'ed off and has a smaller hose running down behind engine to my trans. When i blew my converter and had the transmission dropped, the guys who worked on it said they never saw a 4l60e like mine. They said they saw all sorts of vaccum lines inside of the transmission. But from my understanding, isnt that kind of a thing of the past? I mean i remember reading old transmissions being built that way but not recently.. I do know that the previous owner had it built independently from a guy in texas or something like that who guranteed all his work supposedly and if it blows he'll rebuild it for free? Dont know, dont care at this point im just curious why it was built this way

Anyone with expertise in building 4l60e's or any autos for that matter that could try and explain why my trans was built using vaccum lines.

 

they were most likely using a vacuum modulator to control the tranny instead of a computer. some people like vacuum modulated and some, like myself think its total ****.

 

What exactly does that control then? Before i had it tuned, the converter wasnt locking at WOT, but once my tuner got ahold of it he set it to lock at WOT.

 

The vaccume modulator only controls line presure in stead of allowing the PCM to do it , It does not control shift timing or lockup , It just replaces the presure control solenoid.

 

I was hoping you would chime in haha. Thanks for the info guys.

 

No problem its what I love doing , Helping you guys get answers.

 

There is little bit more to it than what was explained here. If you now know what it is , let me explain why some builders prefer to use Vacuum Modulation instead of a PCM controlled Pressure Control Solenoid.

The PCM uses several inputs from various devices to control line pressure in these units. It is widely understood that for example a TPS or MAF sensor that is out of calibration or reporting erroneously will impart improper line pressure responses which are detrimental to the clutches and band in a 4L60E. Tuners will increase line pressure many times in order to improve shift firmness, when in reality many times that only serves to wear out the individual clutches prematurely. We have seen several units be knocked out by improper Tuning techniques.

A Vacuum Modulator only uses one input to control line pressure. And cannot be affected by Tuning.

These units live and die by line pressure rise, especially in High Horsepower / High RPM combinations. If one were to draw out on a graph the pressure rise on a PCS controlled unit, it would be very obvious that there is a very erratic, not linear pressure rise throughout a WOT pull through the gears. Whereas, a Vacuum Modulator will provide a very, very stable and predictable pressure rise during pulls through the gears.

There is a debate that will go on for some time to coe about whether or not a Vac. Modulator should be incorporated into builds. We strongly believe in using them in High Performance applications.

Hope that helps.

g

 

"These units live and die by line pressure rise, especially in High Horsepower / High RPM combinations. If one were to draw out on a graph the pressure rise on a PCS controlled unit, it would be very obvious that there is a very erratic, not linear pressure rise throughout a WOT pull through the gears. Whereas, a Vacuum Modulator will provide a very, very stable and predictable pressure rise during pulls through the gears."

The person that I use for dyno testing concurs with this statement.