OK IN DETAIL CAN ONE OF THE "BIG 3" BUILDERS EXPLAI HOW A VAC MODULATION UNIT WORKS

.. JUST WANNA LEARN SOMETHING NEW TODAY

ALSO IF YOU HAD A HUGE CAM AND LOW VACCUM COULD THIS LEAD TO PREMATURE CONVERTER CLUTCH AND TRANNY CLUTCH FAILURE


:MY LOGIC IS LOW VAC = LOW LINE PRESSURE

 

Think of Vacuum Modulation as the old school Analog version of todays digitally controlled line pressure. It's not too complicated really.

Low vacuum will produce high pressure.
High vacuum will produce low pressure.

Think about it like this.... at idle or low throttle pressure (high vacuum) the demand on the transmission is not great at all right? But conversely, at a high throttle pressure (low vacuum) the transmission needs to work a little harder therefore we need more pressure.

Hope that helps.

g

 

So No Vac (as In Case Of Disconnected Vac Line)= Highest Pressure ??

 

In That Case A Engine With Low Vac Would Suffer Form Harsh Shifts More Than From Weak Shifts

 

Yes as G says low vac is high presure and high vacume makes low presure, But as you ask theres a bit more. Yes if you have a cam causing very low vacume it can cause the line to be very high unessesarily at low rpm and throttle positions. Also turbos a super chargers can cause this effect. Just as turning the presure up in tuning or excessivly turnng the PCS is bad this to can be hard on the trans unessesarily at low throttle positions. There are work arounds for the turbo situation along with blowers however I am aware of none for low vaccume from a cam. Some people have spoke o vacume canisters and check valves but this would only make a fixed vaccume and eliminate all vaccume contol of presure under these conditions which to me defeats the purpose, Ideally the better system in mY opinion is the PCS but there are some instances where I might consider vaccume modulation , A chronic presure control situation in tuning that cannot be solved would be one (thats what transgo shows it as for in the instructions that comes with it ) and they even say may cause overly agressive part throttle shifts etc.

Hope this helps and dosent confuse. note this information is based on vaccume modulation with the 4l60e and 4l80e not the TH350 and 400 which is quite bit more complicated.

 

Sounds Fun!