Danny.reamer

Ok so I want to swat my th350c to a 200r4. I've done all kinds of reading on here about the swamp and it seems pretty straightforward. But if you questions I have I haven't been able to find on any pages.
1st-I have a 81 so it has the TH350c transmission that already has the electronic locker. Will I need to do anything different to hook up the 200r4 or is it still different?

2nd- I don't really understand the computer part on these corvettes so what tells the transmission to lock up? The reason I ask is because I am getting rid of the original distributor and carburetor so does that have anything to do with it or not
3rd- I'm not sure yet but I'll probably have more questions one members start putting in input

7T1vette

The lockup clutch is activated by a 12 v. signal from the computer (thru a relay). That is the same way a 200-4R and a 700-R4 trans are activated. But, you need to verify to which connector pins that signal is fed. The computer sends the signal to a relay and the relay turns on the L/U clutch.

I am not certain how much of the 'controlling' of the 81's L/U clutch is done by the computer and how much is done by transmission components. Different vintages and types of GM auto trannies managed the L/U clutch differently.

diehrd

If I remember correctly the 81 and the 1980 use a vac switch to send 12v to the converter solenoid . It will be located on the firewall by the break booster ..

mrvette

on the 200 in my '72 SBC vette, the brake switch enables a relay to 'close' when the lights are lit, which in fact OPENS the 12 volt feed to the trans......decisions on when it is to lock up are controlled by the FInj computer.....IF the car in question has FInj on it, I would suspect the computer also was setup to control lock up......just what the computer is looking at to make that decision, I dunno.....I think it's a function of RPM and speed of car.....don't SEEM to be related to engine vacuum....but well could be of course, as there is a suck sensor on the engine.....

SH-60B

I used this:

https://www.bowtieoverdrives.com/cat...php?ITEMID=341

spikebot 81

There are a few ways to achieve lockup and most will cost some bucks. I chose the cheap and simple method. The th350c uses the CCC to control lockup via signals from engine temp and vacuum in combo with the trans pressure switch.

I only wanted lockup to activate when on the highway at freeway speeds. My 2004r locks up in 4th gear only. The 81 system already has the switch on the brake pedal to disengage the lock up when braking so that part of the puzzle is done.

Here is a link from turbo Buick. http://www.v8buick.com/showthread.ph...0-R4-Questions ..

I also installed a rocker switch so I have more control of lockup in 4th gear. I found my 2004r goes into 4th gear at about 45mph and with this 1 wire system, lock up happens within 2 or 3 seconds after the trans shifts into 4th gear. This can cause the engine to lug a bit at lower speeds. I used this switch Moroso 97543. Fits perfectly in the slot for the rear window defrost switch. Now I can put the trans in drive, let it shift normally and when I need to engage lock up flip the switch. Lock up will disengage when the brake is applied or shifting into 3rd gear.