did you take the trimmer head off? try putting it together w/o the spool and spring. take a look inside where the shaft sits, make sure there's no muck in there. it's square so it should slide on.

Thank you for your response...the spool and spring are off and the inside of the tube is very clean. Still no luck.

hi, i'm not sure what your doing wrong. the end of the shaft should be square, it should slide in? pics might help.

Please share
some direct pictures of your issue… Both
Internal and external parts disassembled if possible.

I finally resolved the problem... I taped the outside bearing shaft to the tube so the bearing could not turn even a bit, greased the drive shaft, made sure the plastic insert was down the tube as far as possible then whenever I had time (like when watching television) I would spin and push on the top of the drive shaft. It finally found its sweet spot and dropped in. I can only suspect that the drive shaft and the bearing had worn together for so many years that the drive shaft had to exactly match to the same place on the bearing. Thank you for the help and comments. p.s. there are many youtube videos of this process (search for "trimmer flexible drive shaft") which indicate the process usually goes more smoothly than mine did.