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Jeep Wrangler YJ
YJ General Discussion
Auto to manual swap?
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<blockquote data-quote="machoheadgames" data-source="post: 427803" data-attributes="member: 18789"><p>So that's the thing, I don't know the differences between the auto and manual PCMs. I don't know if there is any timing curve differences or anything to help the engine have a bit more power for the auto. I know the PCMs lock the torque converter on autos and light the upshift light on manuals out of the same circuit. So I believe either PCM can operate with either transmission just fine. I do not know if running an auto PCM on a manual might cause code 37 to pop up which is related to the torque converter not being locked up. I would doubt it because it uses the speed sensor input and compares it to RPM to know if the torque converter is slipping. On a manual the clutch doesn't slip so I'd imagine it won't light the code. So my best guess is the auto PCM would still work. If I were you, I'd probably buy the manual PCM and try it and the auto one and compare. Good info for the forums, and you could always keep the other as a spare if it works, because they are getting hard to come by.</p><p></p><p>NOW, regardless of what PCM you run, you will have to do some wiring down at the neutral safety switch (PNP Switch). The harnesses between manual and auto are the same up until they get to the transmission. The starter relay is grounded by the PNP switch on autos. On manuals, there is a jumper wire feeding the starter relay ground directly into ground so that it starts no matter what. Basically the vehicle harness goes down to the trans and it's the same between all Jeeps. It terminates to a 6 pin plug and is populated by 5 wires:</p><p>-keyed power for backup lights</p><p>-backup light feed to tail lights</p><p>-torque converter lockup wire for autos</p><p>-starter relay ground</p><p>-ground wire for manuals</p><p></p><p>There is a jumper harness specific to your vehicle. On autos, the auto harness plugs in. It has 4 wires. Keyed Power to the PNP switch (for backup lights), and a tail light wire that feeds the backup lights. Put auto in reverse, it connects those two wires together to light up the backup lamps. Coming out of the 6 pin plug are also the starter relay ground wire (which is grounded when you put the trans in neutral or park), and the torque converter lockup wire. </p><p></p><p>The manual has a different jumper harness that plugs into that 6-pin. Two wires come out of the plug and go to the manual trans backup switch (keyed power and feed to the backup lamps). The other wire comes out of the manual harness and feeds right back into that ground. This grounds the starter relay on manuals. So they are grounded no matter what. </p><p></p><p>If it would help, I could probably make you a harness that plugs into the manual backup switch. For the starter relay you would need to snip the ground wire and connect it to the ground wire in the 6 pin if that makes sense. Sorry, throwing a lot at you here but I do believe I understand how it works and can help walk you through it if you have questions. </p><p></p><p>I'm posting the diagrams I found in the FSM. It will make more sense than the rambling I'm doing here. </p><p></p><p>So if you look below, the blue circled plug is the body side. You and I both have that plug on both manuals and autos. If you look at the second pic, it shows the difference between autos and manuals. So for me, I have that blue T22 wire which is the output from the torque converter relay. But I don't have a relay in the plug, so nothing ever happens on that wire for me. You would need to ground your T41 wire (starter relay ground) by hooking it to the Z2 black/orange wire at your body side plug. And then you would want to snip off the PNP switch connector (the 3 wire plug) and run the G5 and L1 wires over to the manual trans switch. The third wire from that PNP switch plug would be the ground that you're hooking up to Z2. </p><p></p><p>Let me know which of that mess doesn't make sense. I can try to clarify further.</p><p></p><p>[ATTACH=full]116783[/ATTACH][ATTACH=full]116784[/ATTACH]</p></blockquote><p></p>
[QUOTE="machoheadgames, post: 427803, member: 18789"] So that's the thing, I don't know the differences between the auto and manual PCMs. I don't know if there is any timing curve differences or anything to help the engine have a bit more power for the auto. I know the PCMs lock the torque converter on autos and light the upshift light on manuals out of the same circuit. So I believe either PCM can operate with either transmission just fine. I do not know if running an auto PCM on a manual might cause code 37 to pop up which is related to the torque converter not being locked up. I would doubt it because it uses the speed sensor input and compares it to RPM to know if the torque converter is slipping. On a manual the clutch doesn't slip so I'd imagine it won't light the code. So my best guess is the auto PCM would still work. If I were you, I'd probably buy the manual PCM and try it and the auto one and compare. Good info for the forums, and you could always keep the other as a spare if it works, because they are getting hard to come by. NOW, regardless of what PCM you run, you will have to do some wiring down at the neutral safety switch (PNP Switch). The harnesses between manual and auto are the same up until they get to the transmission. The starter relay is grounded by the PNP switch on autos. On manuals, there is a jumper wire feeding the starter relay ground directly into ground so that it starts no matter what. Basically the vehicle harness goes down to the trans and it's the same between all Jeeps. It terminates to a 6 pin plug and is populated by 5 wires: -keyed power for backup lights -backup light feed to tail lights -torque converter lockup wire for autos -starter relay ground -ground wire for manuals There is a jumper harness specific to your vehicle. On autos, the auto harness plugs in. It has 4 wires. Keyed Power to the PNP switch (for backup lights), and a tail light wire that feeds the backup lights. Put auto in reverse, it connects those two wires together to light up the backup lamps. Coming out of the 6 pin plug are also the starter relay ground wire (which is grounded when you put the trans in neutral or park), and the torque converter lockup wire. The manual has a different jumper harness that plugs into that 6-pin. Two wires come out of the plug and go to the manual trans backup switch (keyed power and feed to the backup lamps). The other wire comes out of the manual harness and feeds right back into that ground. This grounds the starter relay on manuals. So they are grounded no matter what. If it would help, I could probably make you a harness that plugs into the manual backup switch. For the starter relay you would need to snip the ground wire and connect it to the ground wire in the 6 pin if that makes sense. Sorry, throwing a lot at you here but I do believe I understand how it works and can help walk you through it if you have questions. I'm posting the diagrams I found in the FSM. It will make more sense than the rambling I'm doing here. So if you look below, the blue circled plug is the body side. You and I both have that plug on both manuals and autos. If you look at the second pic, it shows the difference between autos and manuals. So for me, I have that blue T22 wire which is the output from the torque converter relay. But I don't have a relay in the plug, so nothing ever happens on that wire for me. You would need to ground your T41 wire (starter relay ground) by hooking it to the Z2 black/orange wire at your body side plug. And then you would want to snip off the PNP switch connector (the 3 wire plug) and run the G5 and L1 wires over to the manual trans switch. The third wire from that PNP switch plug would be the ground that you're hooking up to Z2. Let me know which of that mess doesn't make sense. I can try to clarify further. [ATTACH type="full"]116783[/ATTACH][ATTACH type="full"]116784[/ATTACH] [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Auto to manual swap?
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