Buick Riviera Wiring Diagram

[Mike Krauss]

New member here and I need a wiring diagram for the 1984 Riviera. Specifically, the circuit for the overdrive unit. Any help would be greatly appreciated.

Mike

[joe_padavano]

There is no "overdrive circuit". The TH325L4 trans used in the 1984 Riv is hydraulically operated. There are no electronics or electrical circuits associated with the fourth gear overdrive.

 

If you are asking about the torque converter clutch lockup circuit, that is controlled by the ECU. The most common failure mode for the lockup circuit is the solenoid valve in the trans.

[Mike Krauss]

Okay, I have this transmission in my '85 Chevy S10. The old 3 speed version finally bit the dust a few weeks ago and I found a 4 speed version to replace it. So, I am looking for a way to manually turn on the "lockup" with a toggle switch. I have written to the salvage yard I got the transmission from to send me the 4 prong molex plug for the transmission. It appears to actually have only three connections. So I need to know how to power them. It looks like (from the exploded views I have seen) that there is a "switch" and a "solenoid" in the valve body area. But I'm not sure how that works. Any insight? 
Attached are some pics of the truck so you can get an idea what I am working with.

Mike 

[joe_padavano]

Just an FYI, the original Toronado TH425 was based on the TH400, just bent in half. Like the TH400, it was bulletproof. The newer TH325 three speed is based on the TH200 and the TH325L4 is based on the 200-4R. Both of those are pretty fragile. I don't know which Olds motor that is, but if it's anything with more torque than a 1980s vintage 307, that TH325L4 isn't going to last long without internal upgrades.

 

As for the TCC wiring, it varies from year to year. Typically pins A and D on the connector are the two sides of the solenoid coil. Pin A is power, Pin D is ground. The other terminal (usually Pin B ) is for the fourth gear pressure switch. In the original application, Pin B was read by the ECU. Pin D was switched on and off by the ECU (GM used a switched ground side circuit). Pin A just provided power with the key in the RUN position. Note that there was also a brake-pedal controlled switch in the power side. This switch is normally closed and opens when you press the brake pedal to ensure the TCC is released in a panic stop.

Edited April 26, 2021 by joe_padavano (see edit history)