Think'n of Buy'n a Big Pusher - ?? Check it out How ??

Hi Mexicowanderer, I had a hard down shift issue with my Allison (.MD 3060 ). And the fix was sloppy throttle linkage at the engine. My rig is 20 years old and with a little adjustment with the trans cable and throttle it shifts like new still.
As you say run it around for a while and have a pro look it over, check for all the repairs, receipts and upgrades and go with your gut feeling about the seller. I am sure there will be more posts with help.