Classic cars reward the senses. The sightlines from a slim A-pillar, the smell of old leather, the way a metal door shuts with a real click. Then you pull into a parking spot and the wheel fights back like a gym machine. Manual steering brings feel on a winding road, but it can turn low-speed driving into a chore, especially once you fit modern tires with more grip and footprint. A well-executed power steering conversion kit can keep the original character while adding day-to-day usability. The goal is not to anesthetize the car, but to reduce parking-lot arm wrestling without losing road feedback.
I have converted everything from 1960s pony cars and full-size sedans to chrome-bumpered sports cars that went decades without assist. The path is rarely identical twice. Brackets sit differently from engine to engine. Header tubes nick universal joint travel by a few millimeters. Steering feel rises or falls based on pump pulley ratio and the quality of the steering universal joint. Still, the fundamentals stay consistent. This guide walks through what matters, what to buy, where installers get tripped up, and how to keep safety at the front of the plan.
What you gain and what you risk
The best conversions deliver three tangible gains. First, low-speed maneuvering becomes normal. With assist, turning the wheel at a standstill requires about a quarter of the effort of a manual setup. Second, the car becomes more inclusive. Drivers with smaller frames or injuries can enjoy it again. Third, if you run wider rubber, especially modern 200 to 260 tread-width tires on a classic, the assist offsets the extra contact patch.
There are trade-offs. Some kits dull feedback around center if the steering box ratio and pump pressure are mismatched. Weight increases slightly, anywhere from 10 to 25 pounds depending on pump type and brackets. A poorly chosen steering box conversion kit can introduce bump steer if the pitman arm arc no longer matches the stock geometry. Sloppy installation, like misaligned shafts or low-quality universal joint steering couplers, can add play or binding. The cure is thoughtful component selection and careful setup.
Choosing your conversion path
You have three main routes, each with a distinct flavor.
Hydraulic assist with a modern steering box. This is the most common power steering conversion kit approach on domestic classics. The kit swaps the manual box for a power box with an integrated valve and higher ratio, mounts a belt-driven pump on the engine, and connects through pressure and return hoses. Good kits include a pitman arm with the correct taper and clocking, a compatible rag joint or steering universal joint, pump brackets, and a reservoir with appropriate return baffling. Done right, this keeps the stock linkage but modernizes assist and ratio.
Hydraulic ram assist on the center link. Some period cars used an external assist cylinder with a control valve added to the drag link. Upgrading to a fresh ram assist system preserves the factory box and steering feel close to stock, but parts availability varies by model. This route works if you are restoring originality or your engine bay leaves no room for a modern pump and box combination. The downside is more joints and potential leak points.
Electric power assist. Column or column-under electric units add assist without a pump, reservoir, or hoses. They save space and weight, and they can be tuned for effort. On European classics with tight engine bays and generators instead of alternators, a column-assist electric unit can be elegant. Electric systems require robust wiring, a solid-state controller, and attention to collapsible column safety. They also change feel differently than hydraulics, often adding effort nonlinearly around center.
The right path hinges on your car’s layout, your tolerance for modifications, and your steering goals. A vintage muscle car that sees highway runs benefits from a quality steering box conversion kit with a 12 to 14 to 1 ratio. A small sports car that values delicacy might do better with an electric column assist tuned for light help only at parking speeds.
Understanding compatibility and geometry
Steering is geometry as much as hardware. If a conversion moves the pitman arm pivot even a few millimeters relative to the idler arm, you alter the tie rod arcs. That can show up as twitchiness over bumps or a tendency to self-steer under hard braking. Good kits keep the sector shaft height and pitman arm length close to stock. Before buying, study dimensions. Reputable suppliers publish sector shaft spline pattern, pitman arm drop, and center-to-center length. If they do not, ask.
The column interface matters just as much. Many classics use a rag joint at the box input. If you move to a modern box with different input splines or offset, you might need an aftermarket steering shaft with a double-D profile, supported by a firewall bearing and a steering universal joint at each change in angle. Excessive angles increase friction and can bind with chassis flex. Keep each joint under about 30 degrees, preferably less. On headers with bulky primaries, plan routing carefully or add a heat sleeve to preserve joint grease.
Pump choice also affects feel. Sagging effort at idle points to low pump speed or insufficient flow. Overboosted, twitchy steering suggests too much pressure for the valve in your box. Many Saginaw-style pumps accept different pressure control valves, and you can change or shim springs to tune output by roughly 50 to 150 psi. For most midweight classics, system pressure in the 1,000 to 1,300 psi range and flow around 2 to 3 GPM provides natural feel, but consult the box maker.
Parts checklist and how to judge quality
A complete hydraulic power steering conversion kit for a box swap usually includes the steering box, pump with brackets and pulley, pitman arm, hoses, a rag joint or steering universal joint, and mounting hardware. Some add an aftermarket steering shaft if the length or joint count changes. When evaluating parts, look beyond paint.
The steering box is the heart. You want precise on-center feel, which comes from tight tolerance in the valve spool and minimal internal leakage. Many kits use rebuilt boxes. Ask how they are tested. A good rebuilder measures input torque to initiate assist, sector shaft end play, and lash across the arc, then documents it. If you see only a fresh coat of black enamel and no spec sheet, be cautious.
The pump and reservoir deserve attention. A pump with an attached reservoir simplifies plumbing and reduces return aeration. A remote reservoir helps if the pump sits low. Either way, baffling and a proper return diffuser reduce foaming, which can cause groan and assist fade. Pulley diameter determines pump speed. If your engine idles at 700 rpm and the crank-to-pump ratio is 1.3 to 1, the pump spins around 910 rpm at idle. That may be too slow with a small displacement pump. Many installers keep a ratio between 1.5 and 1.8 to 1 for good idle assist without excessive high-rpm pump speed.
Hoses make or break reliability. Pressure lines should be rated for at least 1,500 psi with crimped ends. Return lines need proper clamps and should avoid tight bends that trap air. Keep the return port below the fluid line in the reservoir to prevent aeration. I route pressure hoses away from exhaust by at least two inches, or wrap them with reflective sleeve. Heat shortens hose life more than mileage.
At the column end, a quality steering universal joint feels like a precision instrument. No notchiness, no visible slop. If you need two joints, add a support bearing mid-span. Long unsupported shafts can whip slightly under road shocks, which you will feel as a buzz in the rim. An aftermarket steering shaft that uses double-D or splined connections allows clocking and length adjustment while maintaining strength. Cheap telescoping inners can rattle over time, so look for tight tolerance and a real locking mechanism.
Manual to power steering conversion for specific platforms
Not all classics are equal. A few case notes show the spread.
1967 to 1970 Mustang and Cougar. The original system used a ram assist with a control valve on the drag link. You can rebuild that, and it will steer with 1960s flavor. If you want a modern feel, several steering box conversion kit options replace the original with an integral power box using adapter plates. Watch header clearance on small block cars with long-tube headers. A compact pump like a Type II with a remote reservoir eases fitment around the alternator. On the column, plan for a double U-joint setup with an intermediate support bearing if you change the box angle.
Chevy A-body 1964 to 1972. These cars gladly accept a quicker Saginaw power box. With a good ratio, they transform parking and turn-in. Pitman and idler geometry is forgiving, but match the pitman arm length to the center link or you alter effective ratio and tire scrub. If the car uses tall headers, check that the lower universal joint clears by at least a finger width at full engine rock. A simple heat shield can save that joint.
British roadsters. Space is tight, and the charm resides in the steering feel. Electric column assist often wins. You retain the manual rack and pinion, splice an assist motor into the column inside the cabin, and Browse selection program a lightweight curve that helps below roughly 10 mph. Retain the collapsible column function. That can mean shortening the intermediate and ensuring the shear pins or mesh capsule can still do their job in a crash. Use a steering universal joint with proper hardness to avoid brinelling the rack input.
Full-size American sedans. These cars respond well to hydraulic conversions with generous pumps, since the loads at the tire are higher. A large-diameter wheel hides a bit of vagueness, but you can keep feel crisp by selecting a box with firm internal valving and slightly lower flow. On the pump, avoid undersize pulleys that overspeed at highway rpm, which can aerate fluid and heat it excessively.
Porsches and other rear-engine cars. Weight sits on the rear, so steering loads are not extreme, but packaging often fights you. Electric column assist is again the practical path unless you want to retrofit a factory hydraulic rack from a later car. Maintain alignment of universal joints obsessively. A small pre-load in a joint you barely notice at rest becomes a constant nibble on the highway.
Weight distribution and alignment after the swap
Even a small pump and box add mass at the nose. If your car was already pushy, expect a bit more initial understeer. You can offset it with alignment and tire pressure. Modern tires tolerate more caster than bias-ply era specs. On a typical classic with improved control arms and radial tires, I aim for 3.5 to 5.0 degrees of positive caster, about 0 to 0.1 degrees total toe-in for a street car, and a half degree to one degree of negative camber depending on use. More caster improves self-centering, which complements a lighter wheel.
If you add electric assist, weight barely changes, but steering ratio and assist curve still impact straight-line stability. Some controllers allow input speed sensing. With that, you can taper assist above a set speed. If not, select a fixed map that is biased to low-speed help and minimal gain at cruise. People often set too much assist then complain about numbness. Start conservative. You can always add a bit more.
Steering feel is not an accident
The most common disappointment after a manual to power steering conversion is float around center. Three variables interact. Ratio, box valving, and pump pressure. With a very quick ratio, small inputs create large tire angles. That can feel nervous if the box valving is light and the pump pressure high. Rather than chase feel with stiffer bushings or wider front tires, tune the system.
Many Saginaw-style boxes are offered in multiple torsion bar sizes. A stiffer torsion bar inside the valve increases the force required to open the hydraulic circuits, which delivers a firmer on-center build-up. Paired with moderate pump pressure, the car tracks with confidence. On the other hand, a big luxury coupe may benefit from a lighter bar if you want fingertip parking loads. Let the car’s mission dictate the setup.
Fabrication and install notes from the bay
No kit is truly bolt-on across fifty-year-old cars. Holes migrate, frames get repaired, engines swap. A few jobsite patterns repeat.
Mock up the pump and brackets with the belt off. Ensure pulley planes align within a millimeter. Misalignment squeals and eats belts. If you cannot get the right line with your alternator bracket, shim carefully or buy a matched set. On small-block Chevys with long water pumps, mix-and-match brackets cause no end of grief. The right front and rear braces paired with the correct pump snout length solve it.
Notch heat shields before you cut metal. I have watched installers slice a header tube to clear a steering universal joint when a small formed shield would have done the trick. Heat shields and reflective sleeves buy you clearance without compromising the exhaust. If you do need to re-clock a joint for angle, mark both ends and retighten with thread locker once you find a smooth arc.
Do not overtighten rag joints. They are designed to isolate vibration. Crushing the rubber disk removes that. If you move to a solid steering universal joint setup, expect a bit more texture in the wheel. That is normal. If it crosses into chatter, something is misaligned or a joint is at an excessive angle.
Bleed the hydraulic system patiently. Fill the reservoir, raise the front tires off the ground, and turn lock-to-lock slowly with the engine off to purge air from the box. Top off, then start the engine and repeat, keeping an eye on fluid level. If the fluid foams, shut down and let it de-aerate. Persistent foam means the return line is dumping above the fluid level or sucking air at a fitting.
Measure steering stops. After a conversion, you can gain or lose a few degrees of lock. That affects U-turns and can make tires rub. Adjust stops at the lower control arms or tie rod ends if the chassis provides the provision. Better to set a slightly conservative lock than to crease a fender lip.
Safety, legality, and good sense
Steering is a primary safety system. If a failure occurs, there is no safe margin. Use parts from reputable sources with clear load ratings and metallurgy specs on the steering universal joint and aftermarket steering components. Verify column collapse remains intact. Do not weld on steering shafts unless you are trained and follow proper procedures. If you must shorten a double-D shaft, re-machine the flats square and deburr everything. Steering lock hardware, column bearings, and firewall seals should be in good order before you test drive.
On electric systems, fuse the main feed and mount the control box away from heat and moisture. Run heavy gauge wire and a clean ground. A poor ground can create erratic assist right when you need consistency. Many jurisdictions do not regulate steering modifications beyond roadworthiness, but inspections can flag loose joints, leaking hoses, or slop. A clean, well-routed installation not only performs better, it passes scrutiny.
Costs and timelines you can expect
A hydraulic steering box conversion kit with quality components usually lands between 1,200 and 2,500 dollars for parts. Add labor ranging from 6 to 14 hours depending on fabrication, with shop rates dictating the final bill. Electric column assist kits typically cost 1,500 to 3,000 dollars plus installation and wiring. Ancillaries add up. A proper aftermarket steering shaft with two joints and a support bearing often costs a few hundred dollars. Heat shields, belts, fluids, and alignment add more.
Time-wise, plan a weekend if you have tools, experience, and good access. Shops schedule a car for two to three days including road test and alignment. Build in margin for small roadblocks. A seized pitman arm can consume a morning. A bracket that interferes with a power steering pump adjuster slot can spark an hour at the drill press. Patience keeps the work clean.
Tuning and maintenance for the long run
After the first week of driving, retorque key fasteners. Steering box to frame bolts, pitman arm nut, pump bracket bolts, and universal joint set screws all deserve a second pass. Watch for witness marks at the universal joints that would indicate slip. Recheck belt tension once the belt settles. Look under the car for any weeping fittings. A single glazed drop under the pitman area can signal a pressure-side leak that only appears at lock.
Fluid choice matters. Most systems are happy with a high-quality power steering fluid. Some boxes accept synthetic ATF, but only if the manufacturer specifies it. Mixing fluids can create seal swell. If you swapped from ATF to dedicated power steering fluid, consider replacing all seals to avoid unpredictable results. Change fluid after the first few hundred miles to remove any assembly debris, then every few years. Heat is the enemy. If you tow or live in hot climates, a small cooler in the return line extends pump life.
Alignment is not set-and-forget. Suspension bushings age and settle. Recheck toe and caster after 500 to 1,000 miles, especially if you also upgraded control arms or springs. If the car hunts grooves, add a quarter degree of caster or reduce tire pressure slightly. If the wheel does not return after a turn, the caster may be too low, or the box preload might be tight.
When to consider aftermarket steering components beyond the kit
A conversion kit solves the major pieces, but three add-ons often elevate the result. First, an aftermarket steering shaft with properly sized splines simplifies service and lets you fine-tune joint angles. Second, a high-quality steering universal joint with tight lash and proper metallurgy maintains feel and reduces maintenance. Third, an idler arm upgrade with better bushings can tighten linkage, particularly on older domestic cars with flex-prone idlers. None of these replace the fundamentals, but they refine the last ten percent.
There is also the question of ratio. If your chosen box feels too quick for your roads, a slightly slower box with strong on-center valving can feel better. On a light coupe, a 14 to 1 ratio may strike a nicer balance than an 11 to 1, sacrificing a half-turn lock-to-lock for better straight-line calm. Ratios and valving are the language of steering feel. Speak it with confidence, not guesswork.
A practical, minimal checklist before the first drive
- Verify all fasteners on the steering box, pitman arm, pump brackets, and column joints are torqued to spec, with thread locker where required. Turn lock-to-lock with the engine off and wheels up, listening and feeling for any binding, then with the engine running to confirm assist is even both ways. Check hose clearance to exhaust and belts, and confirm the return line sits below fluid level in the reservoir at idle. Confirm steering wheel center on a short road loop, then adjust the drag link or wheel position rather than using toe to fake it. Book an alignment and take temperature readings across front tread after a spirited run to verify even contact.
Where universal joint steering matters most
Universal joints do quiet work. They are also the hidden source of many complaints after conversions. An angle that looks acceptable on a lift can bind when the engine torques over under load. Watch joint angle in three scenarios, static, engine braking, and full throttle. Have a helper blip the throttle while you observe clearance. If the angle approaches the limit, add a support bearing and redistribute the angle across two joints. A small change in shaft length shifts the angle enough to restore smoothness.
Lubrication and sealing deserve attention. Some universal joints are sealed for life, others require periodic grease. On cars that see rain, a simple boot or a shield extends life. If the joint rusts or dries out, the first sign is a faint tick at center then a notchy feel that grows over weeks. Replace, do not nurse it. Steering is not the place to experiment with marginal parts.
The bottom line on making the right choice
A power steering conversion does not have to compromise character. When the parts suit the car and the installation respects geometry, you gain ease without losing engagement. The recipe is straightforward. Choose a steering box conversion kit or electric assist that fits the space and the mission. Use an aftermarket steering shaft and steering universal joint of real quality where the stock column no longer aligns. Match pump pressure and ratio to the vehicle’s weight and tires. Keep hoses cool and calm. Align for modern tires, not 1960s specs. Then drive the car the way it begs to be driven.
If you value patina and originality above all, a carefully refreshed manual system with modest tire widths might be the path. But if you want to share the car with more family, or you just want your shoulders to last, a responsible manual to power steering conversion can extend the car’s useful life by decades. The reward shows itself every time you slip into a tight spot with a light wrist and roll back out with the same old grin.
Borgeson Universal Co. Inc.
9 Krieger Dr, Travelers Rest, SC 29690
860-482-8283