Jim Shea’s Steering Papers



Latest Revision: 07JN2002

CORVETTE C2 AND C3 POWER STEERING PUMP PART AVAILABILITY

The C2and C3 Corvette models are now 20 to 40 years old. All Corvettes with power steering from 1963 through 1982 used the Saginaw P-series “big” power steering pump.

This paper has been written to assist in rebuilding and/or replacing your power steering pump. In order to aid in understanding the procedures that are being described it is recommended that you download additional pictures and text that has been scanned and posted at the websight. Additional pages that you can download are as follows:

P-PumpFlowControlValve.doc

P-PumpLeakPoints.doc

P-PumpBlowUp.doc

P-PumpBenchRepair.doc pages 1,2,3,&4

The exact replacement power steering pump that was used on your Vette is no longer available from General Motors. However, the full power steering pump assembly, or the pump alone, or the correct reservoir alone can be obtained through a number of Corvette suppliers. Prices range from $375 for a NOS 1975 –79 pump assembly to $145 for a 1965 –74 rebuilt pump assembly. Seal kits are also available for around $12.

There is also a source for rebuilding your power steering pump that may just require a trip to your local salvage yard. There are millions of the Saginaw P-series power steering pumps that were used in other General Motors vehicles and utilize many common parts with the Corvette pump. The pumps used in the Chevrolet and GMC C/K trucks and also in the new lines of GM light duty pickups and SUV vehicles are an excellent source of parts. These are the trucks with Chevrolet 4.3L V6, small block, or big block V8s.

These pickup and SUV pumps have internal displacements roughly the same as your Corvette pump. However, the pressure relief settings in these truck pumps are in the 1500 psi range. The setting in your Corvette pump is only around 1000 psi. Now, the flow control valve in the pump also controls the pressure relief setting (Reference: P-PumpFlowControlValve.doc.) Therefore, it is very important that you switch the flow control valve from your Corvette pump into the truck pump so that the pressure relief will be correct. You need to do this because the seals in the control valve and also the pressure hoses used in the Corvette steering system were only designed for 1000 psi pressures.

The “big” Saginaw P-series power steering pump was first used on the 1963 Corvette and its use continued through the 1982 model year. One of the things that makes a power steering pump unique is the fluid reservoir. All P-series pumps have the reservoir sealed with a large diameter o-ring that fits into a cavity on the flange of the P-pump housing. The reservoir is retained by two studs/bolts and the large hexagonal discharge fitting, all three located on the back side of the pump. One marvel of interchangeability, all reservoirs from 1963 to the current model year will interchange from one P-pump to another. Reference: P-PumpBlowUp.doc

The Salvage Yard Approach

If you decide to go the salvage yard route to obtain replacement parts, the good news is that there were literally millions of 1960’s through current model GM light duty pickup type vehicles that were produced with P-series power steering pumps that can donate parts for your Corvette.

Note: This paper assumes that you are familiar with the Saginaw power steering pump and/or are using the Chevrolet Overhaul Manual or some other appropriate reference when performing the procedures referred to in this paper. You can also download the following instructions: P-PumpBenchRepair.doc pages 1,2,3,&4

What to Look For

There are several design factors that you need to be aware of when you go out searching for a power steering pump replacement. Here are the basic changes that occurred through the years that can affect your search for replacement parts.

Integral Steering Fluid Reservoir

Through 1974 the Corvette used a design that had the top portion of the reservoir and the fill neck brazed to the main body of the reservoir. Starting with the 1975 model year, what was called the “ham can” reservoir was used from that point forward. The top portion of the reservoir was all one piece and only the fill neck was brazed in place. It is my belief that either reservoir will function correctly on any of your Corvette models, but for correctness, 1975 is the breakpoint from the one design to the other. Either of these reservoirs will fit on a new pump.

Driveshaft Pulley Installation

Before the 1975 model year, all General Motors power steering pump pulley connections used a 9/16-18 UNF nut, a driveshaft with a male thread and keyway, and a 1/8x1/2 woodruff key. Starting in 1975, a new design interference fit pulley attachment was introduced on all GM power steering pumps. You cannot interchange pulleys or pumps with one connection to the other. The visual pump driveshaft differences make this change very easy to identify.

Conventional Fasteners versus Metric

Before the 1980 model year, all external connections to the power steering pump were conventional threads and fittings. Starting in 1980, all General Motors power steering pumps were converted to metric fasteners. This means that all external connecting parts were now metric.

Metric Stud and Union Reservoir Seals

One other thing, with the conversion to metric fasteners the depth of the stud and union seal cavities in the metric pump housing were deepened. These were the cavities under the heads of the two studs and the pump union. The deeper cavities required thicker square cut seals to properly fill the cavities. Reference: P-PumpBlowUp.doc, #5 Seal “o” ring (Housing) and #19 seal “o” ring (Housing to Stud). Don’t use the old conventional square cut seals in the metric pump housing, they will most likely leak.

The conventional to metric changes included the following:

The discharge fitting on the back of the pump.

Conventional Attachment - 5/8-18 UNF female thread and 45 degree brass flare seat.

Metric Attachment – M16x1.5 female thread with a o-ring port.

You must use the pressure hose assembly with the correct end configuration to fit the appropriate port. Reference: P-PumpLeakPoints.jpg

NOTE! There is an inexpensive aluminum insert that can be purchased and pressed into a 16x1.5mm o-ring pump discharge port. The insert has a 45 degree flare face and essentially makes a mating surface for your old hose as it connects into the more modern pump port. This insert then allows a power steering pressure hose with a conventional 5/8-18, 45 degree flare end to screw into the metric port and seal properly. (You will find that a 5/8-18 UNF male fitting will screw very easily into a 16x1.5mm female port.) The insert is available from:

Lee Manufacturing

11661 Pendelton St.

Sun Valley, CA 91352

818-768-0371 (talk to Tom Lee or his wife)

The four tapped mounting holes on the front of the pump (right behind the pulley). Most pump attachment brackets use one or two of the four tapped holes.

Conventional Attachment – 3/8-16 UNC tapped holes.

Metric Attachment – M10x1.5 tapped holes

The two studs on the back of the pump that retain the reservoir and mount the pump.

Conventional Attachment - 3/8-16 UNC thread into pump housing and the threaded stud. GM #5689546 Stud

Metric Attachment - M10x1.5 thread into pump housing and the threaded stud.

GM #7831388 Stud

Note #1 It is best to keep the same vanes, cam ring, and the rotor & driveshaft together as a set from each pump. If possible, do not disassemble the rotor from the driveshaft.

After you remove the pulley check the area between the pump pulley and the pump housing seal. If it is corroded, polish that area with crocus cloth before attempting to pull the driveshaft and rotor back through the pump housing.

Note #2 If you find that you must separate the rotor from the driveshaft, use the same retainer clip or ring that came with the driveshaft. The early pumps used a clip with a square cut groove in the driveshaft. Starting in 1981, a round wire ring with a rounded groove in the driveshaft was used from then on. The correct retaining device must be used with the appropriate retaining groove.

Note #3 If your pump was leaking at the driveshaft seal and you remove the driveshaft from the pump, now check the surface finish on the driveshaft right under the seal lip area. If it is pitted and corroded or there are grooves in the metal, you must attempt to clean the area by polishing with crocus cloth. If minor surface irregularities cannot be cleaned in this manner, you will have to replace the driveshaft.

Note #4 I strongly recommend refilling your power steering system with genuine GM power steering fluid. There are fluids that are labeled power steering fluid, but the only one used by General Motors as original factory fill is the one I recommend. The amber colored fluid, available from any GM dealer was specifically formulated to work in the Saginaw power steering pump. For maximum durability use GM steering fluid (GM #1050017 32oz).

Specific Exchange Examples

1). Your original pump on your Corvette was made before the 1975 model year:

a). Your replacement pump was also made before 1975:

All parts will interchange between these pumps. Use your original reservoir, flow control valve, spring, union, and studs.

b). Your replacement pump was made between 1976 and 1979:

All parts except the driveshaft will interchange. You will need to use your original driveshaft and pulley with the replacement pump.

c). Your replacement pump was manufactured 1980 or later:

First make sure you get the metric fasteners that attach the front of the pump to the engine brackets. Now check to see if the pump has two metric studs on the back side. These metric studs not only have metric threads where they attach into the pump housing, they also have metric threads where they stick out and attach to your engine brackets. Your original pump had two studs so you need two metric studs on your replacement pump. If you require additional metric studs they are available from your local dealer, or from a Corvette supplier. You will also need two metric nuts to fit the studs. You should use your original reservoir, flow control valve, spring, and union fitting.

2). Your original pump on your Corvette was made between 1975 and 1979:

a). Your replacement pump was made before 1975:

In order to use your original interference fit pulley, you will need to use the driveshaft from your pump. Be sure to use the reservoir, flow control valve, pump union fitting, and spring from your original pump.

b). Your replacement pump was also made between 1975 and 1979:

All parts will interchange. You should use your original reservoir, flow control valve, spring, and union fitting.

c). Your replacement pump was made 1980 or later:

Same as 1). c). above.

3). Your original pump on your Corvette was manufactured 1980 or later:

Your best bet is to find a pump built 1980 or later with metric fasteners and the interference fit pulley attachment. Use your original flow control valve, spring, union fitting, and reservoir.

For the most part, the Saginaw P-series power steering pump is a marvel of design longevity. The basic housing, rotating group (rotor, vanes, and cam ring), pressure and thrust plates have been carried over with only minor refinements through the last 40 years. The other good thing is that Saginaw did a great job of standardizing as many of the pump components as possible. When pump design changes occurred, for the most part, they were introduced throughout all General Motors vehicles at the same time.

A Parting Word

I have (to the best of my ability) gathered the following information from engineering drawings and by speaking to people that worked on the power steering pumps used in the C3 Corvette. Please be aware, a lot of this information is well over 30 years old. Also, you should always follow procedures and instructions provided from shop manuals and other reliable sources when assembling and disassembling the power steering pump.

One last bit of information: If a part to be available through GM dealers, then it is generally also available through numerous Corvette suppliers. You can shop around for the best prices.

A Word About Service Part Pricing

General Motors power steering pumps have many common parts that are interchangeable between various makes and models. If you purchase a part from a General Motors dealer you should not be paying a premium for a Corvette part that is common with other GM vehicles.

A Final Parting Word

Please don’t go running for a lawyer to sue my butt if you purchase a cheap donor pump and something doesn’t work exactly as I describe. In fact, if you have a problem, do other Corvette owners a favor and be sure to get back with me so I can update the information and keep it as accurate as possible.

Also, if you have a favorite supplier that has access to power steering pump parts or complete assemblies and would be a good source to help other Corvette enthusiasts, feel free to share this information. I will be happy to include additional names of suppliers in my Reference List that follows. Contact me at: JIML82@.

Jim Shea

References:

Zip Products

Order Line: (800) 962-9632

On Line Store: zip-

Paragon

Order Line: (800) 882-4688

On Line: corvette-

RIK’S Unlimited

Order Line: (888) 745-7838

Tech Info: (828) 433-6506

On Line:

Dr. Rebuild

Orders Only: (800) 866-9362

Tech Info: (203) 366-1332

Websight:

GM Parts Direct (Flow Chevrolet)

Order Parts Websight:

Tech Info Email: gmpartsdirect@

PumpPartsR&R07JN2002

JIML82@

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