Just picked up a 1996 4020 with 28inch z axis.
We brought it without been able to power it up but the price was right so worth the punt.

The good
Ways look good
Electrically runs fine
1400-5 cpu (upgraded according to the parameter sheet ment to have 1400-4)
-5 axis cards
Turcite on x axis looks good from the little I can see.

The bad
Hasn't been running for near 3 years
Backlash numbers are high z=20 y=25 x=30
After running a dti along the screw I have z.02mm x0.05mm y0.025mm thrust bearings and couplings require replacement and/or inspection.
Y thrust bearings are noisey as and you can feel them through the table so need to be replaced.
Spindle is very noisey just trying to track down if it is coming from the spindle (likely) or the motor(unlikely)
The spindle chiller has been completely disconnected.
55k power on hours
18k cutting hours

The plan of attack
First thing is the replace the y axis thrust bearings and coupling then remeasure backlash. Hopefully the numbers will drop considerably. Then move to the other 2 axis.

Does anyone have any tips for thrust bearing replacement especially y axis as that will be the first on the list.
Cheers