We had to remove the tracks on the D4 because we had several track links lock up on us.  Actually 7 of them. We took the tracks to a track shop to have them pressed apart, but their 200 ton press couldn't move the stuck pins.  They even broke the press pin they were using.  We ended up cutting the tracks apart with the oxy-acetylene torch and replace the pins and bushings in the stuck links. A lot of cutting, heating, pounding with a big hammer and sweat has the tracks fixed.  We have one of the tracks back on the undercarriage. And Dad is driving in the master pin on the other side. My brother is tightening the track.