This forum has convinced me to stick with the original computer in my 81. Was just wonder if it could, handle the lockup function on a 200r4 converter too? I am also thinking of sticking with the original rearend gears too? Not looking to go drag racing just street rippin.

 

As long as your car originally had the lockup function and it still works properly on your stock trans then it will hook right up and work fine on the 200-R4.

Randy

 

The 81 chip was programmed to work with the turbo 350. It will work with the 200R4, but it will lockup at the RPM the T350 was programmed to lock up at

 

So the only way to change lockup rpm is custom chip? Any idea what the original rpm setting is?

 

You may not need a custom chip. There only may be a difference in the lockup points, and if there is it might not be much. But it is something to look into before making the trans swap, especially if you plan on staying with the stock rear gears

 

Heh the th-350c locks up with steady pedal pressure over 35 mph. 35 mph in 3rd gear with the '81 stock rear gears is like 1200 rpm or so. I think he'll be fine.

 

It will work fine, the CCC doesn't know anything about what kind of tranny you have, all it does is tell the tranny it is ok to lock up any a particular time because some conditions have been met, like the coolant temp is up (temp sensor on the manifold)and you have on some speed (speed sensor on the speedo)

 

SIXFOOTER has it correct. You'll probably need to do a couple of simple wiring mods, but the CCC should handle it just fine. The wiring mods are just to cope with the different ways that lockup is done between the two trans types.
Th350c lockup has 12v on pin A of the trans connector & the computer connects the wire from pin D to ground (via the TCC/EGR relay) to complete the circuit through the TCC solenoid.
The Th200-4r I've got (from BTO) grounds the solenoid internally, so you'd need to modify the wiring so that the computer supplies 12v to pin A of the connector when it wants lockup in OD (& 12v to pin D if you want lockup in "3").
I did a wiring diagram for modifying mine which I can email if you PM me your email address (though it was done for the BTO unit, I haven't a clue if other units have the same internal wiring).

 

I used Paul's diagram on a non BTO unit and it worked great.

As long as the lockup doesn't happen in the low gears and at low revs, I doubt that you'd notice any difference in the point at which it locks.

 

That's good to know Always though RPM was the leading factor in when a converter locks. Good thing sharper heads than mine(most everyones) chimed in!

 

Not mine, I'm clueless on the internal workings of them! What I've been told is that the internal pressure switch wired in series with the TCC solenoid in my stock Th350C was there to prevent it energising if pressures were low. If the computer asked for lockup when in the lower 2 gears, or at low speed in top gear, then the switch will break continuity, preventing lockup, as fluid pressure is low. The VSS input to the computer may affect the computer deciding to ask for lockup, but I've been told that it doesn't because the computer is a pretty basic one I wouldn't mind checking that out, but can't as the VSS in my speedo is knackered. I can't be bothered to fix it because
1) The way I've got lockup working now is just how I want it
2) I'd have to remove the speedo, send it to the US, wait for it to be fixed & sent back & then fit it again
3) 2 will cost money I can't afford!
4) No way do I want to disturb the circuits, etc, behind the dash! It was a pita last time I got involved behind there, but everything is working now & I don't want to take any risks!!!!

CA_legal_Vette, Hi. Long time, no speak. Hope things are good

 

hi Paul,

Things are good. Should be trying to start the 73 this weekend if the stars are aligned. How about you? Still working too much?