Copied from PBullys web site. Its sure hard to copy and past here! In the below info you can see they a hydrostatic transmission. The new ones might have 5 or more pumps in them.
https://www.pistenbully.com/fileadm...d/Fahrzeuge/gebrauchte_pistenbully_en__1_.pdf
3PistenBully 100. The multi-talent.PistenBully 100
Model year:1999 – 2010from 2010Engine:Mercedes-Benz
OM 904 LA with elec-tronically controlled fuel injection system (EUROMOT 3A, EPA TIER 3)
Mercedes-Benz OM 924 LA with elec-tronically controlled fuel injection system (EUROMOT 3A, EPA TIER 3)
Cubic capacity:4,250 cm34,820 cm3Power output (ECE):129 kW (176 hp)145 kW (197 hp)
Max. torque:675 Nm at 1,200 – 1,500 rpm705 Nm at 1,200 – 1,600 rpmFuel consumption:from 8.5 l/h
Fuel tank capacity:150 lWidth over tracks:2,500 / 2,740 / 3,100 mm
Width over tiller:from 3,100 mmHeight when driver's cabin tilted:3,020 mmGround clearance:approx. 320 mm
Load area:1,620 x 1,920 mm Tare weight:from 3,600 kg depending on the tracks
Gross weight limit incl. attachments:5,200 kgPayload on platform:1,000 kgSpeed, infinitely variable:0 – 25 km/h
Spec. ground pressure:from 0.051 kg/cm2 depending on the tracksGround coverage with tiller:37,500 m2/h
Brakes:No mechanical wear using hydrostatic transmission. Two multi-disc parking brakes.
Attachments front:Quick change system with All-Way-Blade