One unit, M55997, was converted as a test bed for hydrostatic drive in 1980, was renumbered RDB 975385, and named Laboratory 9 ‘Hydra’.
[5] It was fitted hydrostatic transmission having the normal Leyland Motors 680 six-cylinder engine driving two Bosch Rexroth Hydramatic axial piston pumps.
Each pump supplied fluid to a Volvo fixed displacement compact axle-end motor which drove the axle directly.
This arrangement was only fitted to one bogie, the other one retaining its normal drive but with the cardan shaft disconnected.
The unit was finally withdrawn in January 1986 and scrapped in August that year by Vic Berry at Leicester.