700r4 torque converter lockup
Thread Starter
Instructor
Joined: Oct 2009
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From: Cabot AR
700r4 torque converter lockup
Can anyone tell me how and what information is used by the cpu to engage the tcc. ie what conditions must be met for the cpu to engage the tcc.
thanks
bill
thanks
bill
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
That 'logic' is built into the programming in the computer and would have to be divulged by GM, or a 'past' programmer or technician. Logic like that is usually pretty complex, as it is attempting to eliminate every possible "safety" related situation which might occur during operation. Circumstances of speed differential between engine and drivetrain, calculated acceleration rates of transmission components, braking conditions, etc. all play into the decision-tree for various (electronic) transmission functions. Lockup is usually restricted to steady conditions in upper drive ranges and not under WOT use. It is dropped when brakes are applied, when experiencing high load downshifting, and other operational conditions deemed 'risky' when lockup is applied. It would be best to utilize the computer and all necessary sensor feedback as designed for that tranny to engage/drop lockup, or to buy an aftermarket controller which has undergone extensive design and testing for use with that tranny. If you are 'designing' a switch system for such a unit in your vehicle, your safety with that new tranny is in your own hands. A manual switch in the lockup signal line sure wouldn't do it for me.
Team Owner
Joined: Jul 1999
Posts: 65,492
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From: Orange Park Florida
A 700/4L60 NO e is a much simpler version of a 4L60e or 4L80e which are the only other two possible candidates for a vette....
anything larger will not fit, period.....
so the 700 is much simpler in that the only electronic/electrical control is the lockup....
the typical wiring is so get a brake switch like BWD #S870 the plug on the shark will fit on the brake light switch as per stock, the other switch is wired to a switched 12+ source, like ignition or the yellow wire to the WSWiper..... the other end goes to the 12+ A lead on the 4 pin tranny plug.....pressing the brake pedal now opens the 12 volts to the tranny, unlocking it under any circumstances.....
now most trannies came with a 3/4 or 4th only lockdown switch inside there, that grounds the other end of the coil....AND another wire leading out that goes to the computer for FI of the '80's and then it decides to ground that wire at whatever speed was set at in the chip....say 50 mph for instance....
SOME trannies have a thermal switch in there so lockup will not activate untill temp of whatever is achieved....
anything larger will not fit, period.....
so the 700 is much simpler in that the only electronic/electrical control is the lockup....
the typical wiring is so get a brake switch like BWD #S870 the plug on the shark will fit on the brake light switch as per stock, the other switch is wired to a switched 12+ source, like ignition or the yellow wire to the WSWiper..... the other end goes to the 12+ A lead on the 4 pin tranny plug.....pressing the brake pedal now opens the 12 volts to the tranny, unlocking it under any circumstances.....
now most trannies came with a 3/4 or 4th only lockdown switch inside there, that grounds the other end of the coil....AND another wire leading out that goes to the computer for FI of the '80's and then it decides to ground that wire at whatever speed was set at in the chip....say 50 mph for instance....
SOME trannies have a thermal switch in there so lockup will not activate untill temp of whatever is achieved....
Thread Starter
Instructor
Joined: Oct 2009
Posts: 107
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From: Cabot AR
thanks so far for the info, I'm not redesigning my switch system, I'm reparring the stock one. I installed an 85 700r4 in my 81, tcc work fine untill recently and now I'm tracking down all sensors that provide input to the cpu for engaging the tcc. I know the tps is used, and believe the optical speed sensor nounted on the speedometer is used, is this correct? What other sensors are used by the cpu.
