Mounting Flange and Bolt Pattern
The bolt circle, the pilot diameter and the flange thickness all have to match. Measure the bolt spacing across the diagonal, not adjacent holes, because that is where small differences show up.
Shaft End
Keyed or splined, the diameter, the length and for splines the tooth count and pressure angle. Photograph the shaft end against a rule and we will confirm it.
Ports and Connections
Thread form and size, or flange pattern and bolt spacing. A pump that fits the bracket but not the hoses has not saved you anything.
Rotation
Handed on almost every pump. Look at the shaft from the drive end and note which way it turns. On a vane pump the cartridge is fitted for one rotation only.
Displacement and Control
The displacement sets the flow at a given drive speed, and on a variable pump the control letter sets how the pump behaves. Both come from the model code.
Physical Envelope
Length, width and the position of the case drain. A pump that is dimensionally correct but fouls a guard or a chassis rail still cannot be fitted.
How To Check All Six Quickly
Photograph the nameplate, the mounting face, the shaft end and the port face, and send all four on WhatsApp. Between the code and those four photographs we can normally confirm every point on this list in one exchange.
