There seems to me to be a different solution to your problem. If you look at the drive "box:, you should see 4 separate adjustments. 2 adjust how far UP and DOWN the unit will drive the door. The ones you would want to try to adjust are the UP and DOWN FORCE adjustments.

After lubricating the rollers and tracks (use light oil and not grease), try increasing the down force screw about 1/16 of a turn.

If you have an Owners Manual, I am sure the instructions are inside.

Here is a link to the Liftmaster Owners Manual download site:

http://www.liftmaster.com/consumerweb/service/manuals