vacuum modulator vs no vacuum modulator
05-13-2005, 08:17 PM
#1
Staging Lane
Thread Starter
iTrader: (4)
Join Date: Nov 2004
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
vacuum modulator vs no vacuum modulator Why is a vacuum modulator better then leaving the computer controlled setup and having the computer control the shift points and line pressure???
05-14-2005, 05:33 PM
#4
11 Second Club
What I know is that you want vacuum modulation. Cablebandit hit it right on the nose. I Just dropped my car off at speed, and the tranny I'm getting will be vacuum modulated. 
05-14-2005, 05:35 PM
#5
Staging Lane
Thread Starter
iTrader: (4)
Join Date: Nov 2004
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
yeah i just bought a stage 4 trans without one, do you know how hard it is to install them or just take it to a tranny shop and hope not to get overcharged for it, bc my trans is being installed on the 8th at speed so i only have a short period of time to get that on there.
05-14-2005, 05:39 PM
#6
11 Second Club
I am not sure how hard it is, but I believe TCI (and others) make a kit that will allow you to upgrade to vacuum modulation.
What tranny did you buy? I'm in ~$2,130 for the max evil.
Almost went with the FLP level IV.........
What tranny did you buy? I'm in ~$2,130 for the max evil.
Almost went with the FLP level IV......... 
Trending Topics
05-14-2005, 05:46 PM
#8
11 Second Club
Originally Posted by SSlowLS1
How much is speed inc charging you to install the trans?
I'm looking at ~$3,500 all told.
05-14-2005, 06:04 PM
#9
Staging Lane
Thread Starter
iTrader: (4)
Join Date: Nov 2004
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
speed inc charges 250 for tranny and convertor swap plus fluids, at least thats what i was quoted at, but i need to get a vacuum modulator for the trans before i take it there for the install, anyone know of a high quality one?
05-14-2005, 11:33 PM
#10
A lot of guys use the TCI unit. My tranny guy freaked out when I mentioned vacuum modulation and started in on the horror stories. I haven't heard anything bad on this forum, though. Some people swear by them. I didn't put one in cause I wasn't convinced of the need for it and it was another $100 or so.
05-14-2005, 11:38 PM
#11
Staging Lane
Thread Starter
iTrader: (4)
Join Date: Nov 2004
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
well yeah thats what i dont get, why everyone says there is a huge need for them when the computer regulates the shifts in the first place, how do you like your trans with out one??
05-14-2005, 11:40 PM
#12
11 Second Club
The computer doens't do the greatest job regulating the line pressure. Go back to what cablebandit said in post #2.
Originally Posted by cablebandit
i will say this, after seeing all the f'd up computer controlled line pressure tables, I would not want pcm controlled line pressure if the builder offered to drop 300 bux off the price of the tranny. Vaccum is simple and consistent
05-15-2005, 08:26 AM
#13
look in a stock f-body table where some drop most all the line pressure at WOT....setup like that from GM. You change your maf...like port it, lower load is reported hence less line pressure even though you are prolly making MORE power. Vacuum modulation lets your line pressure rise/fall with REAL load readings....not pcm calculated load. You want pressure to go up and down in sync with your right foot on the gas.
05-17-2005, 06:49 PM
#16
Originally Posted by blindskater02
Why is a vacuum modulator better then leaving the computer controlled setup and having the computer control the shift points and line pressure???
IMO, as long as you go with a tranny builder who has had proven success in his method, it won't matter which route you go.
Gary
05-18-2005, 12:13 AM
#20
Vacuum modulation is an inexpensive, reliable, and easy way out of the work it takes to program the PCM or the TCU to control line pressure properly. Aftermarket controllers like the TCI unit I am running determine line pressure from throttle position, gear, and vehicle speed. With a naturally-aspirated or roots or screw boosted engine this set of variables all stay pretty related to each other. Consistency makes it possible to program it to do exactly what you want. With turbos, nitrous oxide, and even some centrifugal supercharger systems, power output can be different when those factor remain the same. Programming has to have enough overhead factored in to provide enough line pressure for every scenario. The factory computer has an advantage over aftermarket in these applications because it uses MAP as a basis for line pressure. Essentially the same input data the mechanical valve is using manifold pressure, except the PCM factors in other data too. Every built transmission and engine combination will have different optimal programming for line pressure. If you think about it there is some liability in tuning when it comes to this subject. Any PCM can be programmed to catastrophically ruin a $4K transmission attached to it in less than a mile. It's all in how it's programmed. I can't see how forfeiting that tune-ability is an advantage in terms of either longevity or drivability. It's kind of a one-setting-fits-all scenario with the mechanical valve, but if enough people say it's great then it must actually be better, right? That will always depend on who you ask. That's my opinion.