You need to check two other things. 1. Does the problem get worse once the truck gets up to temperature or hot? 2. Does the steering get stiff when the drive gets jerky? One way to check is once the truck gets hot, drive very slowly while constantly turning the steering wheel. At that time both problems should be significant. If so, then the boost pump is no good and there should be no need to buy the pressure test kit. The boost pump is the rear piggyback pump connected to the hydraulic pump, however I think it is only available as an assembly. If you need more info, you can reach me at gitpartsatadelphiadotnet.

Thanks for the reply; serial # H2X352P02313 with Perkins diesel engine. Our Lindes have the foundry package with fire retardant hyd fluid (Quintolubric 888-68 syn. ester type fluid compatible with mineral base type hyd fluid and approved by Linde for use in our trucks). We change the fluid and filter every 1500 hrs which is factory required for units with an extended drive train warranty. I scheduled the local Linde dealer to come out to do the presure testing; but they are having trouble showing up. I contacted the factory; they told me I need to purchase a $1600.00 presure test kit in order to properly test this system. They also sent me a "quick reference check for hydro testing form to be filled out and returned to them. In our case we need to rely on our local Linde dealer support in order to properly troubleshoot this problem; thanks for your help and response; Dave.

what series truck do you have sound like you need to do presure test on the hydrostat could be the boost pump