I'm having my 4L60E built right now, and the shop has talked me into a vacuum modulator conversion. Since I'd already ordered the TCI (actually GMPP) transmission controller, it's a bit of a waste since I won't be able to control line pressure. But then again, I won't have to.

Other than not being able to fine-tune shift quality to my liking, is there any real downside to the vac mod conversion? It seems, especially in a blown application (yes, with a check valve) to be the way to go since you don't have to worry about getting enough line pressure at early throttle positions.

 

I dont know much about it so no help there i'm afraid. but i do have a vac mod. for sale if you are interested. I had a new guy build me tranny and he doensn't like them so he took it out. perfect condition very few miles. let me know what you think it's worth i couldn't even tell you how much i paid for it.