Gravelguy413 Posted March 30, 2021 Share Posted March 30, 2021 Picked up a 12 speed from a salvage yard today that was said to have low miles but who knows. I planned on replacing all of the air lines just because they are old. What else needs to be checked or should be replaced before putting it into the truck? Trying to avoid having to pull it back out to repair or replace something that should have been checked when it was out. Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/ Share on other sites More sharing options...
Brian L Blaylock Posted March 31, 2021 Share Posted March 31, 2021 While you are replacing the air lines I would change the air filter on the back of the transmission this seems to be an item that is often neglected 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/#findComment-471792 Share on other sites More sharing options...
Popular Post mrsmackpaul Posted March 31, 2021 Popular Post Share Posted March 31, 2021 O ring kit on the air rams Input shaft seal Output shaft seal, the bolt on the yoke needs to be done up to 3 gazillion foot pounds and use the proper loctite, don't ask how I know this but it is a heck of job on the side of the road If it's wet at all, even mild damps around the counter shaft caps re seal them And dont use silicone, silastic, form a gasket or any crap like that as when the inside bits ooze inside and drop off the eventually get pumped into the high low sliding dogs and the whole shooting match has to come apart Apart from that, good luck Paul 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/#findComment-471799 Share on other sites More sharing options...
fjh Posted April 1, 2021 Share Posted April 1, 2021 12 speed is a dandy dump truck trans 5 speeds for reverse is a wonderful thing ! some Things to watch for have been mentioned ,to add to the list pull the counter shaft caps check the rear bearings For pitting replace as necessary these can be done with out other disassembly, if you are removing the air shift to re oring check the reverse gears, the idlers also can be replaced or turned around if need be to reused with out to much disassembly the reverse gear and these idlers used to take a beating when drivers were impatient and didn't wait till the truck was static before shifting to reverse! otherwise The trans was decent! Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/#findComment-471852 Share on other sites More sharing options...
Gravelguy413 Posted April 1, 2021 Author Share Posted April 1, 2021 Ok. How about those air valves that are on the top driver side of transmission in the back with the air lines going into them. Should those be replaced while it’s out? Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/#findComment-471889 Share on other sites More sharing options...
fjh Posted April 2, 2021 Share Posted April 2, 2021 they rarely cause issues! Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/#findComment-471902 Share on other sites More sharing options...
mrsmackpaul Posted April 2, 2021 Share Posted April 2, 2021 Check them if your concerned, make up pressure guage with a a tap etc and make sure the air pressure is at 60 - 70 psi Paul Quote Link to comment https://www.bigmacktrucks.com/topic/66411-12-speed-q/#findComment-471925 Share on other sites More sharing options...
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