I was datalogging, and noticed that the computer knows when the car is in fourth gear. How is that accomplished? I am in the process of scrapping my ECM and going with the megasquirt, which can be set to close a lockup relay at a low load condition. However, to use this, I think i will need a f ourth gear switch to only allow lockup in the high gear.

I am hoping that the factory transmission has an indicator switch that I can use to control a relay.
Also, how many amps does a locked convertor pull? I need to get the correct relay and wiring. Thanks!
-Brendan

 

There's a pressure switch in the valvebody that opens when the transmission is in 4th. You can replace it with one that closes in 4th to control the TCC.

 

Lockup is hydraulic. It's just controlled by a solenoid; that is, the electric doesn't actually DO the work, all it does is open a valve to let the fluid do the work. So the current is quite low. No more than 2 amps, and I think actually less than 1 amp. You might not even need a relay.

 

Yeah, running it through the pressure switch without a relay is fine.

 

sweet. Does the pressure switch that is in the transmission open an electrical circuit?
Thanks for the replies!

 

Yes, the pressure switch in most thirdgens grounds the electrical signal to the ECM in 1st, 2nd and 3rd. When the transmission shifts into 4th, the switch opens.

 

Excellent! I have an out. Now I can use a normally closed relay to prevent the convertor from locking in anything but fourth, and still have the unluck at high load. Thanks for the help.

 

The time is here... Does anybody know the wire color for the 3-4 indicator on an 85 mpfi? or, a transmission pinout...

 

 

Does the TCC lockup solenoid require + 12 or a ground to close?
I assume it needs +12v, but you never know.

 

It needs both.

 

the way I had understood it...a ground at pin D locks up tcc. guess I'm wrong...how can I manually lock up tcc???

 

oh ok. The ECM pinout shows one pin to lockup at the ECM. Which pin is that? Ground? That is the pin I will be tieing into.

 

get a volt/ohm meter, on the ohms setting, unplug the connector on the ecm..have someone hold a probe from the volt/ohm meter on that wire(ecm tcc lock up signal)...then You crawl under the car with the other probe and find which wire it is.....thats the best way I can think of...you'd know for sure.

 

The ECM grounds that pin to lock the TCC.

 

Awesome, that is the info that I need.The lockup will be working this summer as soon as I get the spare output contructed on the megasquirt.

 

One final question.
The transmission has a safeguard against locking up in 1st gear correct?
I am debating on whether or not I should use a relay that will ground the TC lockup terminal whenever the 3-4 switch opens, or contructing an extra output on my megasquirt circuit board to add a MAP and RPM condition.
I would use a relay on a key on position, so that the relay is powered whenever the key is in "run". The relay ground will be provided by the 3-4 switch, and the ground pin to the NC position. That way,when the 3-4 switch opens, the relay will return to the NC poistion and ground the lockup pin.
Does this sound viable?
The TC will not be trying to lockup in park while cranking if I do it this way?
Thanks!

 

The TCC apply circuit is fed by pressure from the 2nd gear circuit, so the TCC can't lock in 1st.

 

Ok, got my lockup wired for the most part. I even worked it through the brake so it wont stall on sudden braking.

However, I can't seem to get a ground signal on the 4th gear switch. I can't go fast enough to actually get it in fourth, but what are the chances the 4th switch was already replaced with a N.O switch?