I've read this referenced a few times, and am wondering what it means. Why do/don't we want the torque converter to lock up?

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84 Z28 305 Auto Trans QJ

 

funny you should mention, never seen a torque converter on a manual. dah.

 

A lock up torque converter has a brake in it which allows it to lock solid like a clutch at cruising speeds to eliminate slip and improve mileage.

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87 Formula 350 14.81@91.64
98 Z28 1LE 13.15@107.59

 

We have what is called a Lockup Convertor. When you are driving around the Torque Convertor is Slipping. The Slipping in not very efficient so the Factory started putting a "Lockup" in the Convertor. When you are on the highway the computer will lock the convertor so it doesnt slip anymore. This causes better gas mileage.


The reason it slips in the first place is too allow the engine to climb into RPM better. If the convertor didnt slip it would bog pretty bad till you got up to speed.

Think of it like this. Imagine a Stick Car. Have you ever left from a dead stop and let the clutch all the way out when the engine was at real low rpms. If you floor it what happens? It bogs and takes forever to start moving.

Now what if you "Slip" the Clutch. Only let it out a little. You can rev the engine more and let it get into power before you let the clutch out.

Now the whole point of this is..... When your at Wide Open Throttle the Computer does NOT lock the Convertor.

So you have to ask yourself, if I was driving a Stick car down the track would I run it all the way down with my foot half way in on the clutch? Basically slipping it down the track?? Of Course Not!!!!

So why do it with the Automatic? You dont have too... You can wire in a Switch so you can lock it once you get going.

When I picked up 3-4MPH in the 1/4 just from locking the convertor. It really works...

Hope that helps and doesnt confuse you...


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Mike
1989 Turbo Trans-Am
12.24@112 Street Trim
11.42@119 Race Trim

 

TTA, I'm not sure I understood what you said...Slipping allows you to rev higher and when you lock up the converter it's like letting out the clutch and bogging it down, so it's really only for gas mileage...so why would you ever want to lock up your converter for the 1/4 mile if you want to be rev happy?!

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-'82 Z28 (Pro Street conversion in progress)
-'96 Grand Am (daily driver)

AIM me at: Unitedhope
ICQ me at: 77979548

 

You want it to slip at first to allow the car to get into the usuable RPM ranges. Once its there you dont want the the convertor to slip anymore. It sounds confusing but think about it for awhile.


I dont know how else to explain it but saying its like the driving a stock down the track with you foot half way on the clutch. When you lock the convertor its like letting the clutch all the way out.

Anyone else have a better way of explaining it?


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Mike
1989 Turbo Trans-Am
12.24@112 Street Trim
11.42@119 Race Trim

 

tta how do i wire the switch in i know i have to go into the a and the f terminals under the dash but can u explain what i need to get and how to wire it please? lately at the track i have been just putting a wire in the terminals and pulling it out at the end of the 1/4 but its a pain putting it back in everytime please let us know

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1988 firebird formula350tpi msd 6al box blaster 3 coil accel 8.8 wires flowmaster cat back pro shift light a pillar gauge pod and water temp and air/fuel ratio gauges b&m mega console shifter

 

Check the tech articles for the manual TCC lockup switch particulars.

TTA, your explaination was fair, but not quite historically accurate. The reason for the torque convertor was to provide a clutchless connection between the engine and tranny. The idea was to relieve the driver of the need to operate anything more than the accelerator and brake to get the car going or stopped. They were called "fluid drive" at first, weren't very efficient, so more efficient "torque convertors" were developed using turbine principles.

The "reving up" to which you refer is a beneficial outgrowth exploited by the drag racing crowd. In the 60's automatics were sneared at on the strip. In the 70's, with the advent of bracket racing, the automatic crowd got the last laugh. The locking feature attempts to improve efficiency at cruise, again to be exploited with the manual lockup switch by the racing crowd.

For the record, even a manual switch won't allow the TH700 to lock up in 1st. You have to get into 2nd before the fluid is allowed to be routed to the lockup clutch, even if the solenoid is activated.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 3.08 open, cat-back from '90 305HO, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress.
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Thanks all....

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84 Z28 305 Auto Trans QJ

 

Zippy is DA MAN! He is wise about all topics.