torque converter/ rear end question.....

[paxton350]

ok engine is engine, tranny is tranny but my main question is how do you find an optimal match for your motor/torque converter/tranny/rearend? lets say i have an automatic 4l60e rebuilt, stock rebuilt lt1 with stock torque converter and i think 2.78 gears on a 94 auto. if i plan on blowering this application to to about 6psi (minimal) would it be beneficial to up the torque converter orrrr maybe go to 3.73 gears on an automatic? I know with 4:10 id be cruisin down the street at about 30 mph at like 2500rpm lol right? this is one area i need some schoolin... thanks!

[Craig 94 TA GT]

So I assume your cam is stock specs? If so, then I would say a 2800 stall with 3.73s would be good, but your traction will probably be lousy. It might be beneficial to go with a 9.5" or 10.5" converter because the 12" stock one is heavier and the stall selections aren't great. Also, make sure you get a lockup converter, as a non-lockup will destroy your tranny quickly (3-4 clutches I believe?) Also might be worth it to invest in a tranny cooler if you raise the stall.

Since you have 2.73s, you should probably go with at least 3.42 gears, maybe 3.73s if you can hook up. I don't know how long your rear will last though, but you do have an auto, which helps the life.

[MunsonGTA]

-2500-2800 9.5-10.5 inch lockup converter as mentioned, EDGE makes a great street/strip converter for around 500 bucks.
-tranny cooler
-you'll do fine with 3.73 gears with the auto. i run 3.70 with my 700r4 auto and love them. i'd throw a girdle on the rear end for added insurance. i'm not sure how the carrier setup is with the 10 bolt you have, but i know with the 9 bolt, if you have 2.73 gears, you have a series 2 carrier. and to use gears higher like the 3.42 or 3.73, you have to switch to a series 3 carrier.

[Joe 1320]

ok engine is engine, tranny is tranny but my main question is how do you find an optimal match for your motor/torque converter/tranny/rearend? lets say i have an automatic 4l60e rebuilt, stock rebuilt lt1 with stock torque converter and i think 2.78 gears on a 94 auto. if i plan on blowering this application to to about 6psi (minimal) would it be beneficial to up the torque converter orrrr maybe go to 3.73 gears on an automatic? I know with 4:10 id be cruisin down the street at about 30 mph at like 2500rpm lol right? this is one area i need some schoolin... thanks!

The operating range of the motor determines the rest of the drivetrain. The higher the powerband, the higher the gear you'll want. In your particular application, a stock rebuild won't change the rpm that your motor is performing work. The supercharger is adding lots of torque below the engine's horsepower peak, I wouldn't be so quick to change anything just yet. Forced induction applications with tall gears work pretty well. The same goes for stock stall speed torque converters. There is a pretty good chance that if you up the stall speed of the converter, there is some low end torque that you wouldn't realize, when the load comes up against the converter and you launch, the tires would just blow away. Not really effective. If I were going to do any change, I might go with 3.08 or 3.23s depending on how it flet after testing with the 2.73s. I would only go higher if the heads and cam were changed and that action caused an increase in the operating rpms of the engine. It's at that stage that a higher stall speed converter comes into play. If you really want a little more of a launch without changing gears, you might try a 2400 rpm stall. I still would start with the boost and gradually go from there.

Realize that doing any or all of the above puts your differential at risk of disintegrating. Automatics are a little more forgiving, but if you put out lots of torque and manage to hook.........*Boom*.