1971-1976 GM SCISSOR TOP TEST

Scissor top tests

 

Here are a couple of tests you can do to your 1971-76 full size GM car to help determine which parts may be bad.

 

Side rail test- To test your side rails to see if they are worn, lower the top about 2 feet from the windshield frame. Testing one side at a time try to move the front most edge of the side rail up and down, if it has more than 2 inches of play then you know the main pivot joint is worn out.

 

Actuator (side gears) test- There are several ways to test the actuator gear assemblies, these are the 2 most common. If your top seems to slow or stop part of the way when opening or closing, stop the motor at the point where it seems to bind. Remove the drive cable from the actuator, take a small screwdriver that will fit into the small square hole where the drive cable is attached and try to turn the gear by hand. If you are able to turn the gear and you can feel play or if you see the gear moving in or out of the housing even a small amount then you know it is worn out.

The next test is to lower the top all the way, remove the drive cables from each actuator and disconnect the actuator arm from the side rail link. Grab the actuator arm by hand and push it forwards and back throughout its entire travel. The arm should move with even resistance, if it binds at any point or is very easy to move then your actuator is worn out and needs to be replaced.

 

Drive cables- Remove the drive cables from the electric motor gear box as well as from the actuators, try to turn the inner drive cable in both directions by hand. The cables should turn free with no binding, if you feel ‘roughness’ when turning the cable it may be starting to fray inside and would need to be replaced.

 

#2 bow- The #2 will have ball joint pivot brackets attached to both ends, they are attached to the bottom of the #2 bow as well as being attached to a stud on the side rail. The ball joint pivot brackets are known to pull apart and the #2 bow will not remain in the proper position when the top folds. One other common problem is the side tension cables must have a small pigtail on them that attaches to the end of the #2 bow, if this cable is not in place the bow will not fold properly and can damage the frame or the top material.

 

#3 bow- The number 3 bow should have a plastic glide strip attached to the bottom, this strip is there to keep the side rails from catching and causing damage to the top frame. If the #3 bow glide strip has cuts, cracks or pieces missing you should replace it to keep from damaging your convertible top frame.