Lueke Posted December 23, 2025 Share Posted December 23, 2025 (edited) Hey Guys. New member. But Long time Mack owner. I am restoring an 1989 Superliner. It had a 9 speed in it. I found a 18 speed that was behind an 1991 e9. It came out of a cl series truck. There is a valve on the front passenger side of transmission. Had a couple electrical sensors and all the air lines go to it and one long air line coiled up. I've attached some pictures. Is this a torque limiting solenoid of some sort or was it hooked to the injection pump? Can I bypass it as my old transmission never had it. Edited December 23, 2025 by Lueke Added picture Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/ Share on other sites More sharing options...
Lueke Posted December 23, 2025 Author Share Posted December 23, 2025 20251222_165238.mp4 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587636 Share on other sites More sharing options...
Lueke Posted December 23, 2025 Author Share Posted December 23, 2025 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587637 Share on other sites More sharing options...
Joey Mack Posted December 23, 2025 Share Posted December 23, 2025 just for kicks, put your meter on it and see if its normally open or normally closed. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587644 Share on other sites More sharing options...
Popular Post fjh Posted December 23, 2025 Popular Post Share Posted December 23, 2025 Don't quote me But! I believe this is a neutraling valve for a pto! Puts air to both sides of the split If I remember correctly! try grounding the wire and see if it lights on the dash! 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587646 Share on other sites More sharing options...
Joey Mack Posted December 23, 2025 Share Posted December 23, 2025 that was what I thought too fjh... Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587648 Share on other sites More sharing options...
mowerman Posted December 23, 2025 Share Posted December 23, 2025 I guess reverse lights Seems pretty easy to figure out Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587651 Share on other sites More sharing options...
Joey Mack Posted December 23, 2025 Share Posted December 23, 2025 the switch on top with the 2 wires is for reverse. its a detent switch. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587652 Share on other sites More sharing options...
Lueke Posted December 23, 2025 Author Share Posted December 23, 2025 Thanks for the help so far guys. I should be heading to the shop tomorrow. I can test the switch and see what it is. Reverse switch is above the shifter. Not sure what the sensor with the orange zip tie is. Maybe trans pressure? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587684 Share on other sites More sharing options...
Lueke Posted December 23, 2025 Author Share Posted December 23, 2025 8 hours ago, fjh said: Don't quote me But! I believe this is a neutraling valve for a pto! Puts air to both sides of the split If I remember correctly! try grounding the wire and see if it lights on the dash! Ill look into neutraling valves and see if i can compare them. Unfortunately the trans is in my 89 already so not factory harnesses to diagnose with. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587685 Share on other sites More sharing options...
Mark T Posted December 23, 2025 Share Posted December 23, 2025 13 minutes ago, Lueke said: Thanks for the help so far guys. I should be heading to the shop tomorrow. I can test the switch and see what it is. Reverse switch is above the shifter. Not sure what the sensor with the orange zip tie is. Maybe trans pressure? That's the reverse light switch. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587686 Share on other sites More sharing options...
Joey Mack Posted December 23, 2025 Share Posted December 23, 2025 There is no trans pressure switch.. gear box pressure is vented, not monitored... 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-587689 Share on other sites More sharing options...
Lueke Posted 5 hours ago Author Share Posted 5 hours ago On 12/23/2025 at 8:28 AM, Joey Mack said: just for kicks, put your meter on it and see if its normally open or normally closed. The switch is normally open. No restance on the ohm meter. The wires were all corroded off. So im assuming last owner never used the switch/ sensor for quite some time. Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-588233 Share on other sites More sharing options...
Joey Mack Posted 5 hours ago Share Posted 5 hours ago It was probably for the PTO nuetral switch just like fjh said. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-588236 Share on other sites More sharing options...
mechohaulic Posted 5 hours ago Share Posted 5 hours ago On 12/23/2025 at 6:39 PM, Joey Mack said: There is no trans pressure switch.. gear box pressure is vented, not monitored... vent cover looks to be in front of shift lever ; what would be the purpose of the open disconnected air line fittings on back cover. also enlarging picture , don't see any wires coming from back up light plug ?? Quote Link to comment https://www.bigmacktrucks.com/topic/76254-mystery-transmission-valve/#findComment-588237 Share on other sites More sharing options...
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