The trans shop that rebuilt my trans gave me a 55 psi switch to screw in where the pipe plug is under the governer. Then I spliced it into the the tan and black wire from the tcc plug. It works normal and is alot easier to do. At 55 mph the governer pressure is 55 psi and at that piont the lock-up kicks in. And when you step on the brake it goes off. Hope this helps.
Joe
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10:12 PM
Nov 14th, 2007
fierosound Member
Posts: 15146 From: Calgary, Canada Registered: Nov 1999
Godfather has a 4T60 not the 4T60E. The E trans is controlled by the computer.
Even the 4T60 normally has ECM control for TCC lockup. Shift points and firmness are controlled by the TV cable and modulator respectively. With the 4T60E the ECM controls everything.
So with this switch on his 4T60 it sounds like he's bypassing the ECM controlling TCC lockup.
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08:47 AM
fierosound Member
Posts: 15146 From: Calgary, Canada Registered: Nov 1999
There's a real shortage of good information on the workings of the 4T60 transmission.
There's only 2 external connections for the Fiero's TH-125. TCC lockup power in, and a ground provided by the ECM. The internal 3rd gear switch is a Normally Open pressure switch inline with the TCC solenoid. In order for TCC lockup, the 3rd gear switch must be closed and the ECM grounds the circuit.
I haven't been able to find a wiring diagram for the 4T60 that shows how it's circuit functions. I've heard some talk that the internal 3rd and 4th gear pressure switches are Normally Closed. Checking Pin F on the ALDL seems to indicate this, and the ECM will not cause the TCC to lockup, but grounding Pin F shows the solenoid does work and the TCC will lockup. Anyone have a diagram? Any ideas?
[This message has been edited by fierosound (edited 11-15-2007).]
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05:28 PM
GODFATHER Member
Posts: 1020 From: Summerville S.C Registered: Jun 2003
I have a carb. sbc so the computor is not used. The tcc is wired to the pressure switch. Here's what I was talking about. Sorry I don't have a part # on the switch. It looks like a regulor pressure switch. Try and call a trans shop and ask them.
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07:29 PM
Nov 18th, 2007
fierosound Member
Posts: 15146 From: Calgary, Canada Registered: Nov 1999
Yep. That looks like it. Pics are not showing up for some reason on this trend. The port is right under the governor and by the r/s axle. It's a 1/8 pipe plug. The original plug for the tcc on the th125 trans has a purple wire and a tan and black. The purple wire has power to it when the key is on and when you step on the brake the power is interrupted (off ) and the tcc disengages. The tan and black wire gets cut and you splice it into the switch. So you cut the wire about 3 inches away from the plug and run one section from the plug down to the switch and then run another wire from the other side of the switch back up to the tan and black wire you cut. When the pressure at the switch reach 55 psi it grounds the circut and engages the tcc since theres power to it all the time from the purple wire. At the port under the governor 55 psi is approximately 55 mph. And if you step on the brake the power goes off and the tcc disengages.
Joe
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02:49 PM
fierosound Member
Posts: 15146 From: Calgary, Canada Registered: Nov 1999
119 is the plug where you put the switch. I put a 90 degree elbow and screw the switch into it for frame clearance. It works fine I have no problems with with the tcc working properly. If I gently step on the brake pedal you can see the rpm's go up and you can feel the tcc disengaging. I just drove the car from PA to SC almost 800 miles with no problems. Sometimes we tend to over think things when something seems to easy . The 4t60 is controled by vacuum for its shift points. The TV cable is only for passing gear, the onlly electrical part in the 4t60 is the TCC . The 125 uses the TV cable for its shift points and other variables for the TCC to kick in.
Joe
[This message has been edited by GODFATHER (edited 11-19-2007).]
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05:05 PM
tfwcars Member
Posts: 27 From: oshawa ont can Registered: Oct 2006
thank you for posting some more info on this ,does anyone have any input on the question of the drawbacks of not hooking this up with a carbed engine ...thanks
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06:41 PM
Nov 26th, 2007
tfwcars Member
Posts: 27 From: oshawa ont can Registered: Oct 2006
thank you for posting some more info on this ,does anyone have any input on the question of the drawbacks of not hooking this up with a carbed engine ...thanks
My manual is NOT clear on exactly how the ECM control TCC lockup. One one page it says it needs Brake off, VSS, TPS, MAP and Engine temp inputs while another page in the same manual doesn't list the MAP sensor as a required input. Anyway, if any input is missing or sensor is bad the ECM won't work it properly.
In a carb'd application, if the ECM is still in the car, adding the required sensors will allow you to use the ECM to control TCC lockup. If the ECM is scrapped you need mechanical control of TCC lockup. It can be done as above with a pressure switch and kits can be purchased from Jegs/Summit for vacuum control of the TCC lockup. In any event it is something that would be good to get functioning properly. With highway cruising, it lowers engine RPM and saves gas.
The general consensus of running a modern transmission WITHOUT a working TTC lockup is that it will reduce your gas mileage, increase transmission oil heat and shorten transmission life. http://www.technicalevolution.com/tcc.htm
[This message has been edited by fierosound (edited 12-03-2007).]