Transmissions and Drivetrain Need help with your trans? Problems with your axle?

TQ convertors? whats the need?

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Old Feb 3, 2004 | 09:15 AM
  #1  
Wishmaster's87IROC's Avatar
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From: Winston salem, NC
Car: 1987 1SICIROC.....1999 TransAm
Engine: 385 HSR.....LS1
Transmission: 700R4 with Midwest 3400 2.4str...M6
Axle/Gears: SLP Zexel Posi unit 3.42's...3.73's
TQ convertors? whats the need?

Whats the need for a different stall convertor? look at my combo and also look in the engine tech to see what I currently adding...will having a better stall help me out and not affect daily driving? I really dont understand stalls.....wouldnt that make it so my car would rev and not move in stop and go light to light traffic? what stall you recommend? I have 273's but wanna change that too but til I do what stall? and how would it affect me?

thanks and sorry for repeating......

see ya!
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Old Feb 3, 2004 | 09:30 AM
  #2  
TKOPerformance's Avatar
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From: Newark, DE
Car: '86 Camaro, '02 WRX, '87 K5, '67
Engine: 350 TPI, 2.0turbo, 383 in the works, 289-4BBL, 232, A-head 4-cylinder
Transmission: T56, 5-speed, 700R4, C4, T176, semi-auto 2-speed
Axle/Gears: 3.73, 3.90, 4.88, 3.55, 3.54, 7.00
Change your gears and converter at the same time, or do the gears first. Stick with about a 2,400-2,600 stall and use a 3.73 gear. The improvement will be dramatic.

Most stock converters stall at about 1,800 RPM or less. This is nice an efficient, but doesn't do much for acceleration. A higher stall speed allows the engine to achieve a higher RPM with your foot on the brake before the engine's torque overwhelms the brakes. This means that you leave the line closer to the engines powerband, so the car accelerates quicker.

What stall speed means is the point at which the torque converter achieves a lockup condition where the input side and the output side are spinning at the same RPM. Essentially a torque converter works like a turbine engine with two wheels running in fluid (ATF). The input side recieves engine torque and RPM. This motion is transmitted to the fluid inside the converter, which them transmists power to the output side. Based on fluid shear and the design on the output wheel a certain stall speed is achieved. At this stall speed, and any RPM above the stall speed the converter is acting like a clutch and is transmitting 100% of the engine's power to the transmission (at least in theory).

There is "footbrake stall", which is the max RPM that can be achived and sustained at the line without the car "rolling out" or moving foreward. You hold your foot on the brake and bring up the RPMs until the car wants to roll forward. That's the footbrake stall.

"Flash stall" is another term you will hear. It's bit harder to determine than the footbrake stall. Basically it's the RPM the converter achieves before lockup when you rev the engine without the brakes applied.

With a higher stall converter more heat will be generated, so you need to install an external trans cooler to keep the fluid temp normal or you could damage your trans.
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