1980 Aod Incorrect Shifting

hI,HAVE A 1987 RANGER W/A 1980 LTD AOD & 5.0
from a stop the trans shifts from 1-2-3- before 20 MPH with NO slippage..
at 40 MPH it goes into overdrive but slips going in,it catches,then if acceleratin a little heavy it slips,
fluid is LITTLE OVERFULL,BUT DOES NOT SMELL BURNED, it also has a B&M shift kit in it..
the kick down cable is gone and a spring holds the kick down lever towards the front of the engine, I don't understand if the kick down cable just puts the trans into passing gear or if its like a throttle pressure type set up..
the truck was this way when I purchased it 5 days ago..
anyone know what the fix is for this AOD ??

Try to take it back and see if you have any warranty. This could be a big expense if replacing the shift cable doesn't fix it.

All carbureted 5 liter / AOD combos use a throttle position rod, not a 'cable'.
If the rod is missing, the trans will not work properly.
IMO you should round up a kick down rod from a wrecking yard and install it. Some bracket fabrication may be required, depending on your carb but it should be pretty straightforward.

I do wonder if it was left off because the Ranger engine compartment was too tight and did not allow for clearance. You may be able to modify (bend) a stock rod to fit.