Lockup for Transgo 4L80E FMVB
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TECH Apprentice
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Joined: Dec 2008
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From: Racine, Wisconsin
Lockup for Transgo 4L80E FMVB Just a little info for anyone using a 4L80 without a computer.
I searched for info on this before, but didn't find any details.
The force motor for the converter clutch is normally a pulse width modulated dc signal, but I don't have that available, I just wanted on/off using a switch and the brake pedal. I am almost positive that if you put a straight 14.5V DC (engine running with alternator charging) into the coil it will eventually overheat and burn out.
On my 1994 model, I found the minimum current needed to activate the force motor and lock the converter was .33 amps. I went to Radio Shack and got some of the 100 ohm 10 watt resistors ($1.49 each). I tried one, but it was too much resistance, and only provided .15 amps, I added more, and ended up with four in parallel so they provide 25 ohms resistance. They are pretty big (about the size of a AAA battery each), but they drop the current going into the force motor down to .37 amps, and they don't get hot at all, even after driving on the highway for 30+ miles with the converter locked.
I put them inside a short piece of industrial heat shrink and clamped them to the firewall of my car. They have been working for about 200 miles, including 3 pulls on a dynojet (588 torque/510 hp) in 3rd gear without slipping using a modified stock converter.
Side note: The lockup & OD is awesome with a 3000+ stall speed converter & 3.50 rear gears, I would NEVER go back to a TH400.
I searched for info on this before, but didn't find any details.
The force motor for the converter clutch is normally a pulse width modulated dc signal, but I don't have that available, I just wanted on/off using a switch and the brake pedal. I am almost positive that if you put a straight 14.5V DC (engine running with alternator charging) into the coil it will eventually overheat and burn out.
On my 1994 model, I found the minimum current needed to activate the force motor and lock the converter was .33 amps. I went to Radio Shack and got some of the 100 ohm 10 watt resistors ($1.49 each). I tried one, but it was too much resistance, and only provided .15 amps, I added more, and ended up with four in parallel so they provide 25 ohms resistance. They are pretty big (about the size of a AAA battery each), but they drop the current going into the force motor down to .37 amps, and they don't get hot at all, even after driving on the highway for 30+ miles with the converter locked.
I put them inside a short piece of industrial heat shrink and clamped them to the firewall of my car. They have been working for about 200 miles, including 3 pulls on a dynojet (588 torque/510 hp) in 3rd gear without slipping using a modified stock converter.
Side note: The lockup & OD is awesome with a 3000+ stall speed converter & 3.50 rear gears, I would NEVER go back to a TH400.
Won't burn up the motor. Mine has had a solid 12V (14 running) for about a year/12,000 miles. Before that I had the PCM commanding 100% duty cycle (in theory it is the exact same as solid 12V). No signs of it wearing out yet.
The OP put resistors to get the amperage down for the lockup solenoid, for fear of it burning up. I stated it is not necessary, just put 12V to the transmission, and ground the lockup solenoid to activate.
