ahdoman Posted October 12, 2010 Report Share Posted October 12, 2010 I'm trying to figure out why my Overdrive has stopped working. I'm having a really hard time trying to locate the correct wiring diagram. I can find plenty of places to buy the service manual for an 1989 Dakota but not the Shelby and all I'm looking for is this portion of the wiring diagram (this is from a 1990 3.9). Anybody have it? Also, I think pin 2 is hot and then the computer grounds pins 1 & 3 to engage the overdrive when all of the necessary criteria is met (speed, TPS, etc.)? Can someone confirm this? Link to comment Share on other sites More sharing options...
sdac guy Posted October 13, 2010 Report Share Posted October 13, 2010 I'm trying to figure out why my Overdrive has stopped working. I'm having a really hard time trying to locate the correct wiring diagram. I can find plenty of places to buy the service manual for an 1989 Dakota but not the Shelby and all I'm looking for is this portion of the wiring diagram (this is from a 1990 3.9). Anybody have it? Also, I think pin 2 is hot and then the computer grounds pins 1 & 3 to engage the overdrive when all of the necessary criteria is met (speed, TPS, etc.)? Can someone confirm this? Does your cruise control work? If not and it used to, then it is most likely your speed / distance sensor. If it is bad, neither overdrive or cruise will work. Vehicle will not shift into overdrive until a minimum speed has been reached. It tells that by the speed sensor reading. Same with cruise, if sensor is bad, ecu cannot tell how fast you're going in order to set the cruise. Speed sensor is located at the back of the trans on the tail shaft housing. Link to comment Share on other sites More sharing options...
ahdoman Posted October 13, 2010 Author Report Share Posted October 13, 2010 Cruise control works fine. I've tested all the minimum settings for OD to engage. There may be a conflict between years in the harnesses. That's what I'm trying to determine first. Link to comment Share on other sites More sharing options...
shelbymotorsports Posted October 13, 2010 Report Share Posted October 13, 2010 The 1989 Dakota FSM is what you need. The S/Dakota uses the A-500 transmission that was used on the 3.9 V6 engine. I can tell you that the o/d units "burn up" so there is always the chance it's not electrical. There was a TSB issued around 1990-91 that if I recall correctly had one or two internal fluid holes enlarged so that more ATF could get to the o/d unit for cooling. I want to say my o/d burned up at under 29k miles which was just past the 24k warranty period. When the trans was torn apart for a rebuild the o/d had "blued" from the heat. Steve Link to comment Share on other sites More sharing options...
ahdoman Posted October 13, 2010 Author Report Share Posted October 13, 2010 Thanks Steve. Acording to the previous owner the trans in this car was rebuilt and the changes per the TSB were done. I am still trying to determine why the Shelby OD switch has 5 terminals on it and the harness has 5 wires. The 1990 cab switch only has 4 terminals and 4 wires going to it. I need to determine that difference first to make sure wires aren't crossed up between the two harnesses. That's why I'm looking for the wiring schematic. I could trace everything back through the harness but I really don't have the time. Is the A500 in the Shelby the same as the V6 except for the torque converter? Link to comment Share on other sites More sharing options...
shelbymotorsports Posted October 13, 2010 Report Share Posted October 13, 2010 Thanks Steve. Acording to the previous owner the trans in this car was rebuilt and the changes per the TSB were done. I am still trying to determine why the Shelby OD switch has 5 terminals on it and the harness has 5 wires. The 1990 cab switch only has 4 terminals and 4 wires going to it. I need to determine that difference first to make sure wires aren't crossed up between the two harnesses. That's why I'm looking for the wiring schematic. I could trace everything back through the harness but I really don't have the time. Is the A500 in the Shelby the same as the V6 except for the torque converter? Yes its a stock A500 trans. Send me an email reminder and I'll scan the schematic form the 1989 FSM. Steve Link to comment Share on other sites More sharing options...
shelbymotorsports Posted October 13, 2010 Report Share Posted October 13, 2010 Here are the 1989 wiring diagrams: Link to comment Share on other sites More sharing options...
ahdoman Posted October 13, 2010 Author Report Share Posted October 13, 2010 Thanks for taking the time to do those Steve. Although the info is still incomplete. It looks like a need to buy the 1989 FSM but tell me this; did Shelby use the stock wiring harness from the 1989 or was it modified because of the computer used? In the 1990 schematic it looks like the computer provides the ground on pins 1 & 3 when the proper conditions are met. The schematic you attached doesn't indicate that clearly. Link to comment Share on other sites More sharing options...
shelbymotorsports Posted October 14, 2010 Report Share Posted October 14, 2010 Thanks for taking the time to do those Steve. Although the info is still incomplete. It looks like a need to buy the 1989 FSM but tell me this; did Shelby use the stock wiring harness from the 1989 or was it modified because of the computer used? In the 1990 schematic it looks like the computer provides the ground on pins 1 & 3 when the proper conditions are met. The schematic you attached doesn't indicate that clearly. The Shelby Dakota used the stock V6 Dakota Sport wiring harness with a modification to the sub-harness for the electric fans. In 1990 Chrysler switched form SMEC computers to SBEC computers which is why you are seeing wiring differences. You are correct on the computer grounding a circuit to energize it. Steve Link to comment Share on other sites More sharing options...
Brandonlc86 Posted September 19, 2017 Report Share Posted September 19, 2017 I know this is a 7 year old thread, but it seems to be the one I should ask my particular question in as it pops up in most of my google searching. I also have a Shelby Dakota. #151. Ive been converting it over to carb and I have it running just about perfect. My only snag is the O/D. I stripped the harness to bare bones and tucked back everything I didnt need. SMEC is still intact. In the process I didnt anticipate needing the tps to control od. So what im needing to know is the color of wires for the tps sensor and their function. Ive looked at wiring diagrams but they read like gibberish and are very crude imo. Im running the Demon Street Demon carb that has a tps sensor option that I believe ill be purchasing at a whopping $150!! Im on the fence about just going the PATC route with the pressure switches and such. Im still running the in-tank pump with a fpr to dial the pressure back. Any help would be greatly appreciated. Link to comment Share on other sites More sharing options...
SAI-Steven Posted September 19, 2017 Report Share Posted September 19, 2017 I know this is a 7 year old thread, but it seems to be the one I should ask my particular question in as it pops up in most of my google searching. I also have a Shelby Dakota. #151. Ive been converting it over to carb and I have it running just about perfect. My only snag is the O/D. I stripped the harness to bare bones and tucked back everything I didnt need. SMEC is still intact. In the process I didnt anticipate needing the tps to control od. So what im needing to know is the color of wires for the tps sensor and their function. Ive looked at wiring diagrams but they read like gibberish and are very crude imo. Im running the Demon Street Demon carb that has a tps sensor option that I believe ill be purchasing at a whopping $150!! Im on the fence about just going the PATC route with the pressure switches and such. Im still running the in-tank pump with a fpr to dial the pressure back. Any help would be greatly appreciated. Most people either go with an O/D toggle switch on the dash or the PATC set-up. Although the S/Dakota used the A-500 trans if you Google search " A-518 Hot Rod transmission " you should find people who have installed the similar A-518 trans into their Hot Rod or kit cars where you may find other solutions. You could also revert to an earlier torque-flite 3 speed trans and not mess with the over drive. Steve Link to comment Share on other sites More sharing options...
Brandonlc86 Posted December 8, 2017 Report Share Posted December 8, 2017 Thanks Steve! Ive actually made my own setup. Using the patc pressure switches and a kickdown switch used for a gm th400 trans! Works flawlessly! Link to comment Share on other sites More sharing options...
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