I saw in another post, someone mentioned that a '79 TransAm brake booster could be used as a replacement for a chevelle. It was mentioned that it is a dual diaphram 8" unit. Can anyone else confirm this information and application. I'm looking to replace mine in my 1970 as part of my four wheel disc swap and was curious to know if there was any advantage to this unit over the stock booster.

Looking at Napaonline.com, with a '79 TA with 4 wheel disc, the picture shows what appears to be a small dual diaphram booster. Looks like an 8". Price is $125 plus a core charge.

I put one in about 4 1/2 years ago. What I was looking for was more assist while stopping the car. I had replaced the original style booster and still the brakes felt hard. They stopped well but after a week of stop and go traffic for over an hour each evening, my leg was getting tired. A guy I knew had installed one of these into his wagon and let me try it. I liked the feeling in the pedal a lot better.
I pulled one from a junk yard and took some measurements with it to see if it was going to work. Found out it used the same master as my 72. Used that one as a core for a rebuilt unit. My car is a disc/drum car.
I have more room around the unit than the original booster. Makes it easier to play with even the small block I have.

i can verify this as i had a 78 or 79 trans am WS6 parts car i stripped down. i still have the booster and it is the 8" unit.

i have never driven a car with one of these boosters, so i cant comment how they work or feel. but i have heard that they require more vacuum to operate because of more diaphram area, but in turn they create more assist than a standard booster.

Yes, it is everything you said it was... but be careful! Those little dual-diaphram guys take more vacuum to operate than the larger single diaphram ones! You need like 15" of vacuum to get one working right. BTDT.

Bill C.

Correct, but I run a stock engine so I have enough vacuum to operate it. If you use this booster or one of the more expensive aftermarket brake boosters you need vacuum. One way to solve the problem, if you don't have enough vacuum, is to install a vacuum booster.

Originally posted by BC:
i have never driven a car with one of these boosters, so i cant comment how they work or feel. but i have heard that they require more vacuum to operate because of more diaphram area, but in turn they create more assist than a standard booster.

Bill C. Actually, more diaphram area requires less vacuum to operate. The power that a booster produces is equal to the vacuum times the surface area.
The question is, do those boosters really have 2 8" diaphrams? They look like they've got an 8" and then another, smaller one.

I was having problems with my single 9" booster with 14" of vacuum. I went to a dual 9" from True Connections and solved the problem. I tell ya, this is the ultimate booster.

http://www.true-connections.com/cat/page76.htm

I have one sitting in my garage that i will sell for $35 plus shipping.