From the stock of over 1400 M113 infantry fighting vehicles, or Spz and Kdo Pz 63, a total of 625 vehicles were subjected to combat value enhancement measures from 1973 onwards.

Within the framework of the so-called retrofit program, hundreds of infantry fighting vehicles and command tanks were overhauled. The most obvious improvement was the installation of a Swedish-made gun turret. The MG's came from liquidated Vampire and Venom of the Swiss Air Force. Furthermore, additional tanks were added to the rear, and new loading arrangements for baggage and radio equipment were created. From then on, the vehicles were designated Spz 63/73.
With the introduction of the Pz 87 Leopard, the escort vehicles of the Panzergrenadier formations had to be adapted. A total of 382 vehicles were again completely upgraded. This was done by means of a stronger engine and chassis, additional smoke projectors and, most visibly, the new front and side armor in conjunction with the camouflage paint.

The military designation was Spz 63/89, and this quality improvement meant that the vehicles remained in service until 2005, when they were gradually replaced by Hägglunds' Spz 2000.

Spz 63/89Technical data:

Unladen weight:13'500 Kg

Length: 5'400 mm

Width: 3'000 mm

Height: 2'570 mm

Engine: GM 6-cyl.turbo diesel

Displacement: 5'220cc

Power: 265 hp

Top speed:65 km/h

‍