MACKS Posted November 23, 2019 Share Posted November 23, 2019 Tranny works perfect all summer as soon as the temps drop it's a pita to get it to go into reverse,sometimes I have to put in forth neutral for bit before it will shift,air pressure is set at 60 psi at the selector,correct lube in tranny,any ideas? Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/ Share on other sites More sharing options...
MACKS Posted November 24, 2019 Author Share Posted November 24, 2019 A friend of mine has the same problem with his six speed,no ideas? I was thinking maybe some oil residue in the shift cylinder making it stick when cold.. Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436559 Share on other sites More sharing options...
fjh Posted November 24, 2019 Share Posted November 24, 2019 (edited) 20 hours ago, MACKS said: Tranny works perfect all summer as soon as the temps drop it's a pita to get it to go into reverse,sometimes I have to put in forth neutral for bit before it will shift,air pressure is set at 60 psi at the selector,correct lube in tranny,any ideas? I would be checking the air pressure at the shift lid forward hose on the small cyl should be around 70 psi ! you could also as stated remove the end of the rev cyl and check for oil build up! also due to its age consider removing the shift lid and re oring the whole unit ! Not really that hard to do in a CL ! Edited November 24, 2019 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436562 Share on other sites More sharing options...
MACKS Posted November 24, 2019 Author Share Posted November 24, 2019 6 minutes ago, fjh said: I would be checking the air pressure at the shift lid forward hose on the small cyl should be around 70 psi ! you could also as stated remove the end of the rev cyl and check for oil build up! Thanks if I remove the rear cover on the cyl can I slide the cylinder out to clean it up,I'm thinking no,I gotta look in the book.. Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436563 Share on other sites More sharing options...
fjh Posted November 24, 2019 Share Posted November 24, 2019 (edited) 16 minutes ago, MACKS said: Thanks if I remove the rear cover on the cyl can I slide the cylinder out to clean it up,I'm thinking no,I gotta look in the book.. No the lid would have to come off to do it correctly! If you remove just the small rear cap it would be just a look see thing!to clean out any oil ect! you can try it! Edited November 24, 2019 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436565 Share on other sites More sharing options...
JoeH Posted November 25, 2019 Share Posted November 25, 2019 Oil delivery truck I've driven in the past the synchros didn't work for ****. They started parking it in the garage, 70 degrees synchros work great!.. Check the oil chart for your trans to see what oil to run given your ambient air temps. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436634 Share on other sites More sharing options...
david wild Posted November 26, 2019 Share Posted November 26, 2019 While my engine warms up i use either 4th or 5th with neutral switch and let tranny warm up too. it really helps on cold days. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436647 Share on other sites More sharing options...
Rob Posted November 26, 2019 Share Posted November 26, 2019 I've had three of my trucks do that. Usually have to select reverse in neutral, then pull shifter into gear. Sometimes have to do the same to shift from reverse back to forward too. Problems were always pronounced when cold. As stated remove top cover and install all new O rings and I'd wager your problems will go away. 1 Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/59937-12-speed-reverse-problem/#findComment-436648 Share on other sites More sharing options...
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