Im looking to swap out my tranny. Right now its a 700r4 it has been good to me. All it has is a shift kit and it has been 9.68 @ 140mph. i want to take it out so i can run a transbrake. any of you guys run a powerglide on the street? id like to run that tranny but seems like a th400 would be better for the street. i do drive it and racing on the street. just want to know what you guys think

 

Many years ago when powerglides were street transmissions, people yanked them out to install the new TH350 when it came out. They wanted that extra gear which was lower than the glides. If you have enough hp, and it looks like you do, you don't need the torque multiplication of a lower first gear to get you moving like a low HP engine needs.

I run a glide on my race car and I've seen cars that run similar ET's run TH400's. The TH400 is heavier and eats more HP but offers a low first gear to increase torque off the line compared to a glide. I run 4.86 gears in my diff for the torque multiplication. Through a 1.76 first gear, that gives me a 8.55 ratio. A TH400 with a 2.48 first gear through 4.10 gears gets 10.17. That's more torque multiplication off the line and it doesn't need the deep gear ratio in the diff. Even using a modest 3.73 gear, it still gets a 9.25 ratio. If I put 5.14 gears in my diff, I'd only get a 9.04 ratio.

Of course it all depends on how much torque your engine puts out. Too much multiplication and you can easily spin the tires no matter what you try.

 

yea my car goes 10.90 on motor and then 9.68 on spray thats with my 700r4 on a footbrake. with a trans brake it should go better. the powerglide sounds nice but just worried it wont be good on the street.

 

Option C:

A 2004R like the turbo T/A and Buick Grand Nationals run. There are guys running in the 8's with them. A quick trip over to TurboBuick.com will give you direction to the guys who build them.

The advantage is the 2.76 first gear (a tad deeper than the TH400) and still a useable overdrive for long street cruises. Many guys hook the trans brake up internally (sort of stealth) so that it comes on when you put the transmission in 1st. They spool up and then shift to 2nd to release the brake. Of course, the trans still starts in 1st gear... That with a 3.90-ish rear gear ought to keep you pulling the front wheels regularly...

Anyway, just my two cents. I hate losing driveability when you don't have to. I can understand why the above 87 IROC runs a powerglide, why not? He's not driving across town, much less across the state, without a trailer. It's all about what you will do with the car. I just don't understand why anyone runs without overdrive on the street these days. There are manual and automatics available for any horsepower range that the street can handle...

 

...cause some of us are running around 1500hp on the street once you hit that point, the idea of fuel economy and OD is kinda out the window, but we're not talking anything that gets driven very often. - I'm a bit lost as to how a t-brake would work like that, but I've never f'ed with a 200r.

Art Carr does affer a manual valvebody w/ t-brake for a 700r4, but personally, I wouldn't be worried about having OD in a car that needs a t-brake and manual vb.

personally, I'm not a glide person. We broke way too many very high $ units. I've seen some take some serious abuse though(Lynch's outlaw car, though it's a leased trans and gets rebuilt after evey event). I'm gonna run a T400 in my dr class car and we're running a t400 in our 10.5 outlaw car.