[jonathonar89]

Besides being a rear deck shade, do rear window louvers serve any aerodynamic purpose? I could theoretically see a properly designed window louver adding downforce to a spoiler (rear end) at higher speeds...couldn't find any threads on the subject.

I'm considering a 2.73 gear behind a 4 speed in my '79 T/A

[David Holmberg]

The short answer would be no.

Air (at speed) is flowing over the roof and then hitting the rear spoiler. If anything it would stick up in the air causing a disturbance.

Most of the rear louvers from the 70s were plastic, with a few of them being aluminum.

[73 TRANSAM]

I had a 3.23 on a Super T10 back in the day and I must say that a 2.73 gear will only be good on the freeway. Your car would lug around on that gear unless your engine has a lot of lowend power. Also the louver has a tendency to fly out when doing a high speed run.

[NBF823]

Originally Posted by jonathonar89

Besides being a rear deck shade, do rear window louvers serve any aerodynamic purpose? I could theoretically see a properly designed window louver adding downforce to a spoiler (rear end) at higher speeds...couldn't find any threads on the subject.

I'm considering a 2.73 gear behind a 4 speed in my '79 T/A

Interesting. I don't really know. But it'd be interseting to find out.

I'd think only the top louver - depending how it was designed, could possibly add any real down force. But I think what may happen here, is the whole - all of the louvers would just serve to disrupt/seperate the airflow over the back of the car, possibly creating more drag for a given amount of downforce, and being the the airflow is now disrupted and seperated- reducing the downforce potential of the rear spoiler. - Just thinking out loud.

[oldtinsmith]

I looked in a book by Fred Puhn: How To Make Your Car Handle (Pro methods for improved handling, safety and performance. How to set up chassis for highway, road course, drag or oval track. Practicle data, formulas and instructions).
On page 173 of the book, he talks about a rear spoiler (the spoiler is usually mounted low on the body behind the rear window). The air at this point is totally separted from the body surface and is extremely turbulent. A spoiler requires reasonably smooth air flow to work effectively.
Many rear spoilers on production cars are for looks only. If you want a rear spoiler to work on the road it must be quite large, and even then it won't do much for you at legal speeds!

Doug

[GTOLou]

Originally Posted by jonathonar89

Besides being a rear deck shade, do rear window louvers serve any aerodynamic purpose? I could theoretically see a properly designed window louver adding downforce to a spoiler (rear end) at higher speeds...couldn't find any threads on the subject.

I'm considering a 2.73 gear behind a 4 speed in my '79 T/A

You could go w/ a super T-10 that has the 2.88 first gear. Might get away with it. I've run that tranny/gearset combo (briefly) in a car w/ a 3.08 rear. 2nd gear (1.91) was just too "low".. but, may be okay w/ that rear gear. Also, the 2.88 first gearset has a pretty big drop-off from 2nd to third gear.

[jonathonar89]

Originally Posted by GTOLou

You could go w/ a super T-10 that has the 2.88 first gear. Might get away with it. I've run that tranny/gearset combo (briefly) in a car w/ a 3.08 rear. 2nd gear (1.91) was just too "low".. but, may be okay w/ that rear gear. Also, the 2.88 first gearset has a pretty big drop-off from 2nd to third gear.

I just bought a new 2.64 cluster gear for my t10...hopefully it works out well if I indeed go that route. Been battling the court system lately so I'm going to have to hold off on replacing the rest of my gear box.

[Bigger is Better]

Originally Posted by David Holmberg

The short answer would be no.

Air (at speed) is flowing over the roof and then hitting the rear spoiler. If anything it would stick up in the air causing a disturbance.

Most of the rear louvers from the 70s were plastic, with a few of them being aluminum.

I agree with David, you want the air to flow cleanly over the roof, down the back window and to the rear spoiler, from there you build a high pressure zone over the rear deck. The window spoilers will redecue that rear down force.