what is going on when tq is "locked"
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Joined: Sep 2005
Posts: 441
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From: lewisvilee NC
Car: 89 RS camaro
Engine: 454 swap in progress
Transmission: th400
Axle/Gears: 4.11
what is going on when tq is "locked"
i have a 89 carbed 350 that use to be FI and i keep reading post that say if you switched to carb and unhook your ecm that converter wont lock up. and that you can run a toogle switch and what not to make it lock up in 4th gear. what i want to know is how do i know if i already have some kind of rigged setup that will make my converter lock up, what is happening when it locks up and, why is it better to have it locked up? 
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Joined: Sep 2002
Posts: 9,192
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
OK - I'm no expert, but as I understand it ...
Normally, the ECM locks torque converter at low rpm's when in 3rd or 4th gear.
The "locking" process is actually a solenoid inside the tranny, that redirects enough fluid into the converter it's two halves from spinning at different rates, thus a 1 to 1 ratio is acheived between engine RPM's and tranny input shaft RPM's.
Anytime the converter is not locked, there is some slippage between the two halves of the converter, meaning some power wasted (ie not getting to the wheels)
This "locking" of the converter allows for:
1) better gas mileage and lower engine RPM's since no engine revolution is wasted on spinning something that does not directly translate to wheel movement (ie the slipping of the one converter half against the other)
2) lower tranny temps, since there is less heat from friction from the two halves slipping
OK - I'll let the experts chime in and tell you what I missed or where I'm wrong
There are many methods available to lock it - from a simple chunk of wire and a toggle switch, to aftermarket kits available for $80 - $200. I installed a TCI kit in mine, was $80, works automatically based on vacuum rather than the ECM, and allows for switch install to regulate it manually - but requires tranny pan removal - there are many others with various options available. For the cheap DIY route, search on here - there are many threads about doing it yourself.
Normally, the ECM locks torque converter at low rpm's when in 3rd or 4th gear.
The "locking" process is actually a solenoid inside the tranny, that redirects enough fluid into the converter it's two halves from spinning at different rates, thus a 1 to 1 ratio is acheived between engine RPM's and tranny input shaft RPM's.
Anytime the converter is not locked, there is some slippage between the two halves of the converter, meaning some power wasted (ie not getting to the wheels)
This "locking" of the converter allows for:
1) better gas mileage and lower engine RPM's since no engine revolution is wasted on spinning something that does not directly translate to wheel movement (ie the slipping of the one converter half against the other)
2) lower tranny temps, since there is less heat from friction from the two halves slipping
OK - I'll let the experts chime in and tell you what I missed or where I'm wrong
There are many methods available to lock it - from a simple chunk of wire and a toggle switch, to aftermarket kits available for $80 - $200. I installed a TCI kit in mine, was $80, works automatically based on vacuum rather than the ECM, and allows for switch install to regulate it manually - but requires tranny pan removal - there are many others with various options available. For the cheap DIY route, search on here - there are many threads about doing it yourself.