1987 SEL 420 Automatic Transmission

[mack_fulton]

I have a 1987 SEL 420 Automatic Merc and the transmission won't change gears. I have changed the filter and gasket and filled it up with new fluid. Would the electric module have anything to do with the car not changing gears?

 

[guydewdney]

this transmission is mechanical - its a 722.3xx gearbox. i note from the other thread you say it does 1st and second - but not 3rd and 4th....

check vacuum hoses - theres one to the LHS of the box

check kickdown cable (rhs of box) is connected - it should have some resistance when pulling the end of the cable at the throttle end

check kickdown valve (back right of box) and switch (under pedal) - disconnect valve (plug near propshaft on box) to make sure switch isnt stuck on...

take off valve assembly (last resort) - and clean it. be VERY careful. do ONE valve at a time on a very very clean bench. theres about 20 valves, and each valve has 5 components to it - there are no real diagrams for the order - so if you have a digi camera take a picture of each one as you take it out. it will take you all afternoon (i know - ive done it on my GF's sprinter box which is the same). valve body is the 8" square ally box in the sump of the gearbox - take off sump and filter (again - sorry) and it just unbolts. theres a tiny little plastic valve on the top which you musnt lose...