The initial models were developed from the early hydraulic Traxcavator models built by the Trackson Company to fit on to Caterpillar tractors. The Traxcavator name was used by Caterpillar on the early machines they designed and built after acquiring the Trackson company.
The Caterpillar 977D was introduced in 1955 to replace the Caterpillar No.6 Shovel add details of the series
- Caterpillar 977D Crawler Loader - 1955 - 195?
- Caterpillar 977E Crawler Loader - 195? - 1960
- Caterpillar 977H Crawler Loader - 1960 - 1966
- Caterpillar 977K Crawler Loader - 1966 - 197?
- Caterpillar 977L Crawler Loader - 196? - 197?
A few examples are known to survive in UK collections;
- S.E. Davis & Son collection has a 977H in full working order that can be seen at some working events (photo above)
- Russell Saywell collection also has a 977H in full working order (Photo below)