Columbia Overdrive

H

harvsfl

Member
What is the first thing to check for when the overdrive does not engage. It worked after the 2nd or 3rd attempt at the start of the trip, but would not engage on the return.
Thank You for any help I can get.
Harvs
 
the shifting unit may be sticking and in need of some lube, if so MMO works well. The shift unit has a diaphram with a leather seal. The seal should be well lubed. Also check that the columbia is filled to the bottom of it's fill plug.
 
Pull the hoses off the shift canister and if they have oil in them the small seal on the 5/8" shaft is worn. The seal can be found at a local supplier of seals. Also there are 2 leather cup seals back to back in the canister that need to be lubricated as mentioned above. Marvel Mystery oil works best, all other oils tend to make the cylinder gummy even needsfoot oil. They also like to be driven 4 or 5 miles before they shift good. Make sure the rear is filled to the new filler plug on the Columbia side of the rear. G.M.
 
You do not say what year Columbia you have, the 46-8 shift valves have diaphrams which crack with age and leak vacuum and will cause a failed shift. What ever, the cause 99 percent of the time will be a vac. leak somewhere, not mechanical problem.
 
I discovered the overdrive switch wire had come off the ignition switch. It's working ok now. I did give it a shot of mmo while checking it over. It is a 47. Sorry for the omission.
Harvs
 
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