OJ Avery Posted November 28, 2018 Share Posted November 28, 2018 I'm having trouble locating in the parts manual which solenoid this is. Allison 4500. 13 Mack GU I don't have the breakouts I need to really diagnose it, boss wants to see if just replacing the solenoid will save a trip to the Allison dealer. Thanks!! Quote Link to comment Share on other sites More sharing options...
Mackpro Posted November 28, 2018 Share Posted November 28, 2018 There was a Allison Guru on either a school bus fourm or a motor home forum that had lots of good tech info on the Allison’s . Quote Link to comment Share on other sites More sharing options...
Challenger Posted November 28, 2018 Share Posted November 28, 2018 Have you replaced the trans fluid and filters? Seems like people overlook trans fluid and filters. Fun fact- The original trans filters say “factory installed”. Quote Link to comment Share on other sites More sharing options...
OJ Avery Posted November 29, 2018 Author Share Posted November 29, 2018 yes, unit has had oil and filters changed. Was in here in June for same code. Looked a little deeper and its a pressure switch. I actually found a ohm value for it when I googled it so I'm going to drop the pan and see what I see. Quote Link to comment Share on other sites More sharing options...
OJ Avery Posted November 29, 2018 Author Share Posted November 29, 2018 Having no luck on replacement procedure for the ps1 switch. Winging it Quote Link to comment Share on other sites More sharing options...
Ncranson Posted March 7, 2019 Share Posted March 7, 2019 If it is a factory transmission make sure to remove the solenoids from the aluminum part of the valve body and check for broken trim springs. Quote Link to comment Share on other sites More sharing options...
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