Td23 Posted November 2, 2015 Share Posted November 2, 2015 Ive got an 88 DM688sx with a maxitorque 5 speed. Transmission has 4 hours on the rebuild with no issues until it took a few tries to get it into reverse. I'm not sure what's going on here because when there's less than 60 psi in the tanks the reverse shifter engages no problem but once the truck builds over 60lbs the shifter won't engage. I'm not sure if I should replace the valve in the shifter head or if I should pull the reverse shifter apart. Any advice would be appreciated. Thanks Trevor Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/ Share on other sites More sharing options...
mrsmackpaul Posted November 2, 2015 Share Posted November 2, 2015 Welcome to the forumcould be a number of things but I would start with simple things firstis the air regulator hooked up the correct way ??did something get in the air lines when the box was out and cause a blockage ?if you apply shop air strait to the air ram on the box does it shift ok ???Paul Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/#findComment-309833 Share on other sites More sharing options...
Td23 Posted November 2, 2015 Author Share Posted November 2, 2015 Regulator is hooked up right. I pulled the lines back off to see if there was any visible blockage. I just can't figure out why when I have more air in the system the shifter won't engage but when I don't even have enough air to release the parking brake, it engages fine Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/#findComment-309837 Share on other sites More sharing options...
Timmyb Posted November 3, 2015 Share Posted November 3, 2015 What is the air pressure supposed to be regulated at for the shifter? Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/#findComment-309853 Share on other sites More sharing options...
Td23 Posted November 3, 2015 Author Share Posted November 3, 2015 (edited) 70 psi if I'm not mistake. I'm not sure if this little pressure reducing valve bolted on the side of the trans is messed up or what Edited November 3, 2015 by Td23 Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/#findComment-309887 Share on other sites More sharing options...
Challenger Posted November 3, 2015 Share Posted November 3, 2015 What was the problem before the rebuild? I assume there is air at the reverse fitting when under 60psi since it shifts. Is there air at the reverse fitting when above 60psi when not shifting? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/#findComment-309932 Share on other sites More sharing options...
Monk31 Posted November 11, 2015 Share Posted November 11, 2015 I have 84dm688sx I had a rebuild on trans done I broke the main shaft on trans I had the same problem after rebuild brought back and it was leaking air bolt was missing installed bolt and it worked after that properly . Every once in a while it won't go I flip lever a couple times it will pop in check for missing bolts. does your truck drop air pressure quickly ?Sent from my iPhone using Tapatalk Quote Link to comment https://www.bigmacktrucks.com/topic/42469-reverse-shifter-problem/#findComment-310942 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.