Chevrolet A-Car Fast Ratio
Power Steering Gear Upgrade
Authored by Jim Shea, Revised June 16, 2002
CHEVROLET A-CAR FAST RATIO POWER STEERING GEAR UPGRADE
INTRODUCTION
This paper is written to assist Chevrolet A-car owners in locating parts and components that can be used to install a fast ratio steering gear in their vehicle.
Most Chevelle A-car vehicles that were built in the 1964 through 1974 time frame came from the factory with Saginaw Steering Gear Division model 700 power steering gears. Most had gear ratios in the 15:1 range. A listing of 1964 through 1974 Chevelle power steering gears with ratios, efforts, t-bar size, and travel is available from the website where you obtained this paper or from the author.
With modern radial tires and performance suspension enhancements, many enthusiasts would like to improve their steering gear ratio to a rapid 12.7:1. The steering ratio of a steering gear is the number of degrees that you rotate the steering wheel (and therefore the gear input shaft) in order for the output shaft to rotate one degree. The lower the ratio number, the faster the steering. This paper is written to assist Chevrolet Chevelle, El Camino, and Monte Carlo enthusiasts in swapping their slower ratio power steering gears for a fast ratio 12.7:1 model 700 power steering gear. Please note, there is a new Saginaw model 600 power steering gear that is also available with a 12.7:1 ratio. However, this gear is not interchangeable with the model 700 gear.
Recommended replacement model 700, 12.7:1 ratio, Saginaw recirculating ball gears are listed on the following Excel spread sheets: (click here)
1985–1996 Caprice, Monte Carlo, & Buick Fast Ratio Gears
1967-93 Camaro Power Steering Gears
1968-93 Nova, Monte Carlo, Chevy II Power Steering Gears
1964-1974 Chevelle Power Steering Gears
1992-98 Jeep Grand Cherokee Fast Ratio Gears
I do not recommend Camaro fast ratio gears because they have restricted travel and generally have high steering efforts. They can be disassembled and the travel restrictors removed but that is best left to someone very familiar with rebuilding Saginaw recirculating ball steering gears.
THE SAGINAW RECIRCULATING BALL POWER STEERING GEAR
The Delphi Saginaw Steering Systems (formerly Saginaw Steering Gear Division, GMC) recirculating ball, model 700, integral power steering gear is a marvel of longevity. The basic concept and most major components that make up the gear assembly started production in the early 1960s and are still being manufactured today.
There are a couple of interface areas that have remained the same from 1964 to the present. Let’s look at the attachment areas that you will not have to worry about if you decide to make a fast ratio gear installation. The three tapped gear mounting holes are in the same location and are the same thread (7/16-14 UNC) all the way from the middle 1960’s right through today! The pitman shaft serrations and the pitman arm lock nut are still the same. So this gear will bolt up right to your frame and your power steering pitman arm and steering linkage will bolt right on as well.
Some of the changes that did occur throughout the years of production are as follows:
1). The input shaft was reduced in diameter from 13/16 inch OD to ¾ inch OD in 1977. 2). Starting with the 1980 model year, the inlet and outlet ports on the gear were converted from conventional 45 degree flare fittings with 5/8-18 UNF and 11/16-18 UNS female ports to o-ring connections with 16x1.5mm and 18x1.5mm female threaded ports.
All of the fast ratio steering gears that we are looking to swap into our A-cars were produced between 1982 and 1998. Therefore, in order to install a fast ratio gear in your car, you will need to accommodate the above listed changes.
Let’s review the interface parts one by one:
GEAR INPUT SHAFT TO FLEXIBLE COUPLING
The original steering gear in the 1964-1974 A-car had a 13/16 inch OD input shaft with splines and a flat. The new fast ratio gear has a ¾ inch OD input shaft. We will need a new flexible coupling to connect to the gear. The following vehicles were produced with flexible couplings that will attach to the new gear:
1977 thru 1982 Chevrolet and GMC C/K (2 wheel and 4 wheel drive) Pickup
Trucks
1977 and 1978 Camaro, Firebird, and Nova
1979 Nova
1983 thru 1986 Chevrolet and GMC C (2 wheel drive only) Pickup Trucks
I have found a flexible coupling in the GM parts system that will connect to a ¾ input shaft. It is available through GM dealers. It is part number 7826542. It is fairly expensive (around $80 list) but it is brand new.
Be sure to get the attaching pinch bolt, nuts, and lock washers when you purchase the flexible coupling. Flexible couplings attach to the steering gear with a special pinch bolt (#7807271). This bolt can be purchased from any GM dealer. Make sure that you use this correct bolt to fasten the flexible coupling to the gear. Please note, if the column flange is also detachable, you may require still another one of these special pinch bolts.
STEERING COLUMN TO FLEXIBLE COUPLING
Another thing that we have to take into account is that the A-car steering column and the connection to the flexible coupling went through a couple of design changes between 1964 and 1974. These differences will also need to be addressed.
1964, 65, 66 STEERING COLUMNS
The 1964 - 66 Chevelle steering columns had a long steering shaft that extended from the end of the steering column down toward the steering gear. Some of them had a detachable column flange, others had a stamped flange that was staked in place. The flexible coupling on the gear bolted to the steering column flange. This early flexible coupling was different from new couplings in that it had two different diameter stop pins and the two special 5/16-24 UNF attaching bolts. The newer flexible couplings have different sized attaching bolts (one 5/16-24 UNF and the other a 3/8-24 UNF) along with equal sized stop pins. In order to attach the new flexible coupling to the old design flange you have two areas that require modifications. One involves the mounting bolts; the other requires additional clearance to one of the stop pins.
THE FOLLOWING APPLIES TO A DETACHABLE FLANGE:
Place the column flange on a table so that the face that mounts to the flexible coupling is down. Place the pinch bolt slot at the 12 o’clock position. You want to drill out the hole that is at the 9 o’clock position to 0.381 diameter. Do not enlarge the hole too much. The 3/8-24 bolt on the new flexible coupling has a fairly narrow shoulder that must seat against the column flange. Just enlarge the hole until the threads on the 3/8-24 bolt just pass through. This is the modification I prefer because now the column flange will only assemble to the flexible coupling one way. You don’t run the risk of having your steering column attached upside down.
The other choice is to remove the larger bolt (the 3/8-24) from the new coupling and replace it with a one of the special 5/16-24 bolts that you can remove from your original flex coupling. Use the original four tanged retainer to keep the bolt in place. Since the column flange can now be assembled either way, you now have to remember that the 35 year old 5/16-24 bolt goes into the hole located at the 9 o’clock position on the column flange.
The last modification that you will have to make is to open up one stop pin clearance notch on the column flange. With the column flange in the same position describe above; take a look at the stop pin clearance notch located at the 6 o’clock position. You will need to take a file or a high speed grinding tool and increase the size of the notch by 0.070 inch around its entire shape. (See Figure #1). This will gain you clearance around the large rivet on the new coupling and both clearance notches should now be about the same size.
THE FOLLOWING MODIFICATIONS APPLY TO A STAKED, STAMPED FLANGE:
You basically are going to modify this stamped flange similar to the instructions above for the detachable flange. However, you will be working from the coupling side of the flange (opposite from the detachable instructions). You will probably have to remove the column in order to gain access to the stamped flange. You will first have to open up the smaller of the two stop pin notches by the same 0.070 inch (same as above). Now, after opening up the stop pin notch and looking at the flange from the coupling side, locate the bolt hole that is counterclockwise from the revised notch and drill it out to 0.381 inch diameter.
1967 THROUGH 1974 STEERING COLUMNS
These Chevelle steering columns either had long, collapsible, steering shafts that extended down to the gear from the end of the steering column or they had separate, intermediate steering shafts that bolted to the column up by the dash. In either case, both type shafts have column flanges that attach to the flexible coupling. These column flanges should have two different sized bolt holes and clearance notches for two large rivets. Therefore they should be compatible with your new flexible coupling without any modifications. (See Figure #2)
POWER STEERING PUMP – PRESSURES AND FLOWS
Where the Saginaw model 700 gear is known for its longevity, the Saginaw power steering P-pump has been around an equally long time. You most likely want to use your original pump with its reservoir and pulley. The good news is that your power steering pump can be quite easily upgraded for pressure and flow to work with your new fast ratio gear. The fitting on the back of the pump regulates the amount of oil flow from the pump. The flow control plunger, (which is inside the pump directly behind the fitting) controls the pressure relief. These parts are very interchangeable between various Saginaw P-pumps.
The Chevelle power steering pumps (before 1970) had relatively low pressure relief settings (950 psi). With modern wide tires and a fast steering ratio steering gear, you will probably want to increase the pressure relief setting of your pump. 1970 and later pumps had pressure relief settings of 1400 psi, so they should be very adequate.
Also, from 1964 through 1969 the Chevrolet power steering pump outlet incorporated a male fitting and therefore required a pressure hose with a female nut to connect to it. Starting in 1970 the fitting was converted to a 5/8-18 UNF female port with a 45 degree flare seat (the same as the rest of GM). Since your new fast ratio gear has metric ports you might even consider getting rid of either of the previous fittings that you have in your original pump and converting to a 16x1.5mm metric discharge fitting as well.
If you can obtain the pump that originally came with your fast ratio steering gear, this is the safest and best approach toward obtaining the discharge fitting and the flow control plunger that will give adequate flows and pressures for your steering system.
Another approach is find a P-pump used in Chevrolet and GMC C/K trucks that were built after 1979. Also the new lines of GM light duty pickups and SUV vehicles have P-pumps that can be used. These are the trucks with Chevrolet 4.3L V6, small block, or big block V8s. These pumps will all have 16x1.5mm metric discharge fittings.
However, if you have an early P-pump (1964 through 1969) and still want a 5/8-18 UNF female fitting with a 1400 psi pressure relief , you will need to find a P-pump from a 1976 through 1979 four wheel drive K-truck (not the two wheel drive C-truck).
Once you have the pump that you want, you will need to remove the discharge fitting that screws into the back of the pump. Then, you need to probe inside the discharge cavity and using a magnet or just tipping the pump you should be able to remove the flow control plunger (See Figure #3). This is the device that sets the pressure relief and it will interchange right into your original pump. First assemble the spring then the flow control plunger. Note, make sure that you orient the plunger so that the screen side of the plunger goes into the pump first (nest to the spring).
POWER STEERING HOSES
I don’t have any expertise with aftermarket power steering hoses. So I am not familiar with what types of end configurations, bends, etc that are available. If you are able to get the set of hoses from the vehicle that supplied your fast ratio gear, you might get lucky. They just might fit your car!!!
The most straightforward approach would be to use power steering hoses with metric fittings that screw directly into the ports of your fast ratio gear. Modify your pump as described earlier to also use a metric female discharge fitting.
However, there is another alternative. Lee Manufacturing sells small aluminum inserts that can be press fitted into steering gears with metric pressure and return ports. You use the original hoses with the 11/16-18 UNS and 5/8-18 UNF nuts and 45 degree flared ends. Since the metric and conventional threads are very close to each other you will find that the 5/8 nut screws very easily into the 16mm port, the 11/16 nut may need a little persuasion but it also will screw into the 18mm port. The face of the insert is cut at a 45 degree angle, so the old hoses will seal against it. There are two different inserts (#40620 - pressure) and #40630 - return) and he sells them at a reasonable price.
Lee Manufacturing
1661 Pendelton St.
Sun Valley, Ca. 91352
(818) 768-0371 (talk to Tom Lee or his wife)
As described in the pump section, you can also quite easily modify your pump for either a female 16x1.5mm o-ring port or to a female 5/8-18 UNF 45 degree flare port by finding the appropriate pickup truck P-pump.
SOME WORDS CONCERNING POWER STEERING FLUID
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. 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).
SOME PARTING WORDS
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 systems used in your Chevrolet A-car. Please be aware, a lot of this information is well over 30 years old. Also, you should always follow procedures, instructions, and torque recommendations provided in shop manuals and other reliable sources when assembling and disassembling the components in your power steering system.
Please don’t go running for a lawyer to sue my butt if you purchase a cheap donor part and something doesn’t work exactly as I described. In fact, if you have a problem, do other Chevelle and Elky owners a favor and be sure to get back with me so I can update this information and keep it as accurate as possible.
Figure #2
Figure #3