At one time, the only power steering available on trucks was laughingly referred to as the “Armstrong” style. That meant that if your arms didn’t look like Popeye’s, cranking the wheel around could be tough because the driver was the only source of power steering. Today things are different, and thanks to steering swaps and rack-and-pinion conversions power steering is easy to add to most trucks. But while power steering swaps are common, so are complaints concerning steering sensitivity. The problem usually comes about from mixing and matching components or using pumps that “over-assist” the steering gear.

In most cases a Saginaw is the power steering pump of choice. As Jeff Grantmeyer at Borgeson explains it, the Saginaw self-contained power steering pump was used widely by all Big Three auto manufactures from the ’60’s on up into early 2000. Over the years there have been many different variations of this, but they fall into two general categories—the self-contained “canned ham” pump with an integral reservoir, and the Type II with a remote reservoir. About the only version that’s not commonly used is the “P-Series” pump found on early fullsize cars and Chevy/GMC medium-duty trucks.

Pump Basics

Pump pulley shaft: The Saginaw self-contained pump was offered with two different pulley shafts. The 5⁄8-inch nut retained keyway style shaft was used from its inception until 1974 and the ¾-inch diameter “press-on” style shaft used from 1975 and on.

Pressure hose connection: The Saginaw self-contained pump was offered with two different high-pressure hose fittings. The 5⁄8-inch flare connection was used from the beginning until 1979 and a 16mm O-ring connection was used from 1980 on.

Pump mounting studs/holes: The mounting studs/holes changed on the same timeline as the pressure fitting above from SAE to metric.

Pump reservoir: The Saginaw self-contained pump was offered with way too many hose-return-fitting configurations. The hose-return fitting varied completely by original vehicle application. Some reservoirs had returns running up, back, left, right, forward—well you get the idea. The Saginaw pump reservoirs were even offered with two return fittings for vehicles with a Hydro-Boost brake system.

Pump flow/valve rating: This is another aspect of the pump that varied completely by original application. The OEMs would specify what flow rating was required based on vehicle weight, steering gear piston diameter, and whether or not the pump was running a Hydro-Boost brake system. The Saginaw pump in OEM applications can be set from 2.0 on up to 4.5 gpm.

Pump bypass pressure: Just like the flow rating above, the OEMs would specify output pressure based on the original vehicle application and what system the pump was running. Most steering gear applications would run between 1,100-1,300 psi with heavy vehicle high-demand applications on up to 1,550-1,600 psi. Rack-and-pinion steering, on the other hand, is generally happier at a lower operating pressure of 850-950 psi.

Excessive response/touchy steering: This is generally caused by excessive pump pressure, Borgeson offers a pressure reduction kit (part number 899001) that will allow the customer to adjust the internal bypass pressure of the P/S pump (self-contained and Type II with a remote reservoir).