Hey guys,
The computer on my '81 just sits there doing nothing, as I have replaced the carb and distributor with aftermarket, non-computer-controlled parts.  Still have a lockup torque converter though.  So, I've been thinking of ways to use the lockup feature.  Below are my ideas.  Anyone have better ideas or opinions on these ideas?  By the way, I'm running a 2000 RPM stall.  Thanks!

1) Use the B&M kit that attaches a small cable between the tranny and speedo cable to sense the car speed and activate the lockup at a set speed between 30 and 90 mph.

2) Build a little latching relay circuit and use a momentary push-button switch mounted somewhere that would activate the lockup whenever I wanted, then only a tap of the brake would deactivate it.  If I did this, I would like to bypass the "3rd gear only pressure switch", so that I could try out activating the lockup once I got up to maybe 4000 RPM in 1st gear to see just how firm the upshifts would be.  Any tranny experts have an opinion on whether that would be a reasonable thing vs. something that would be ####### the tranny?  (Even w/ the Transgo shift kit, my shifts are soft and the 2-3 shift is slow. Never had a TH350 before, but experiences w/ a TH400 were that it was firm and fast...)

You're not gonna be able to get lock-up in first gear anyway, so that idea is moot. Even if you did the valve body mods that would allow you to do it, you would wind up ripping the splines out of the converter if you engaged it at 4000 rpms in 1st, and it shifted into 2nd.    

Here's what I would suggest you do....
Change the pressure switch on the valve body to a higher rating...say 55. This equates to around a 55 mph lockup speed. The pressure switch comes in many different ratings, so you can tailor the lock-up to come in whenever you want it to, and still be released when you hit the brakes. The switches have numbers on them, such as "35", or "28"...these numbers are the pressure at which the switches close. So...a 25 switch would close at 25mph, and allow lock-up. A 45 switch would close at 45mph, and your lockup would be at 45, and so on. I prefer to run 48, or 55 switches.
This would the the quickest,and easiest thing to do.

If your trans is not shifting like you think it should, something ain't right, especially if it has a "Shift Kit" in it. You may want to replace the modulator with a new one, and/or do some adjusting on the screw that fits inside the vacuum nipple. Turning the screw IN will make the shifts later, and firmer. Turning it OUT will make them softer, and earlier.

Thanks for the advise Adam.  That helps, but the one remaining issue is that I need something to replace the computer to tell the TCC that it is OK fo rit to lockup.  Since I am not using the computer, I was thinking about using the switch and the "latching relay" circuit I mentioned above.  Anyone seen a better idea?  I know someone makes a manual control for the newer lock-up auto transmissions, but I haven't seen anything for the TH350 other than the B&M control that uses the speedo cable to determine the car's speed.  Doesn't sound like a bad system, other than  it costs $170 and I'd rather have a cheaper solution...

All the pressure switch set-up needs is a 12v source...once the pressure switch closes, it grounds the LU solenoid, and the unit will go into lock-up. Once the vehicle gets below the speed the pressure switch closes, it will cancel the lock-up. It's a pretty simple, no hassle deal. The switches are not that expensive, either, so you could get a few different ones to tailor the lu speed to where you want it.
The lock-up would also dis-engage if you hit passing gear, so it wouldn't be lugging the engine.
All you need to do to change the switch is remove the pan, unscrew the switch, and replace it with the new one....painless. Adams' Apple2008-02-27 11:26:57

Joel,  dwright2008-02-28 10:04:00

DaveW, the '82 cars all had the 700R4 overdrive trans...the '81 is a 350C, three speed with lock-up.
The 700 can be made into a non-computer controlled lock-up also, but it takes a little more than just swapping a pressure switch.

I assume I need that info. Any help you can give me will be greatly appriciated.

Adam, just to clarify...
I assume what you call the "pressure switch" is the same thing my TH350 book calls the "3rd gear only switch"?  Almost has to be, as there are only three things in the circuit, the computer, the solenoid, and this switch in question.  So, you are saying that, instead of letting the computer supply the 12 volts to the pressure switch when it deems appropriate, just supply 12 volts to the pressure switch constantly and then the ONLY determining factor in turning the lockup on is the car's speed.   Is that correct?
Thanks!

Oh, forgot, there is a 4th device in the circuit: the brake cutoff switch.  Can I just bypass that and run the 12 volts constantly and directly to the pressure switch?  I assume the difference then would be that, if I had a "55" switch and was driving 70MPH and hit the brakes, the TCC would just not disengage until the speed dropped below 55, then it would.  I don't see a problem with that.  Sound correct?
Thanks a lot.  You've been a huge help!

John, you are correct...with one small difference. The ECM actually supplies the ground for the circuit. The solenoid has 12v all the time the key is on(and the brake off). Then, when the ECM sees a specified speed, it provides a ground. If the pressure switch( which could be called a 3rd gear switch) closes in 3rd, it completes the circuit, the solenoid closes, blocking the fluid from exhausting thru it, which causes fluid pressure to stroke the lock-up valve, which in turn applies the clutch in the torque converter.
You could use the brake switch as it is, to supply the 12v source to the connector. Then you would indeed be able to dis-engage the converter clutch when the brake was pressed. That is really more of a personal preference thing, tho. Some like it like that, some don't care. My opinion is they seem to work best when wired direct...once it hits the speed that closes the switch, it locks up, and stays locked until it slows down. If you hit passing gear, the converter will unlock, because the trans is now in 2nd, instead of 3rd, which means the pressure switch is now open.


DaveM...I can P/M you the info on your 700, but I'm sure this has been discussed somewhere here before. I'll look for the thread, but I'll also send you some info via P/M.