Hi Pert, thank you for the reply.
Well I figured out what the problem was. The motors I have for the z-axis are to low in torque for directly driving the 5/16" threaded rod to lift the y-axis.
The other thing is I can't find in any of the RepRap Mendel90 documentation or on the RepRap forum were it states "you need a stepper motor with minimal X-torque" to drive a 5/16" or 8mm threaded rod. If they had only put something in the documentation it would have save everyone a lot of time.
I did find a web page with a calculator that was last edited in Dec 2018.
Because of the low torque motors it really didn't mater what setting I put in the Marlin firmware or how high I raised the current. They were just never going to turn the all thread correctly.
My only saving grace is that I have the two original chassis from the Beckman dot matrix printers, that have the original set of 4cm gears to drive the paper feeder roller. I will use the gears and chassis to make a gear box for the stepper motors to drive the 5/16" all thread.
So my first redesign. This is why I like building things, I learn the knowledge and to me that's priceless.
Thank you, Kenn.