Yukon Gear 08-10 Ford F250/F350 Super Duty Power Steering Gear Box (Input Shaft - Double Flat)

If your 2008, 2009 or 2010 Ford F-250 or F-350 Super Duty wanders between the lane lines, needs constant small corrections on the highway, or has a steering wheel that moves an inch before the front tires respond, the steering gear box is a prime suspect. The Yukon Gear & Axle ZSG7631 is a brand-new (not rebuilt) power steering gear box built for these trucks, made under Yukon's USA Standard Gear line, with the double-flat input shaft the 2008-2010 Super Duty steering shaft couples to. There is no core to send back.

What the steering gear box does in a 2008-2010 Super Duty

On these trucks the steering column does not push the wheels directly. The column's intermediate shaft turns the input shaft of the gear box, which is bolted to the frame rail. Inside, a worm and ball-nut assembly converts that rotation into a short swing of the sector shaft, and the pitman arm on the sector shaft drives the drag link and tie rods. Pump pressure routed through a rotary valve inside the box does most of the work, which is why a heavy truck still steers with light effort. When the ball track, sector teeth or valve wear, the wheel gets slack in the center, effort becomes uneven, and the truck stops tracking straight. This unit is specified at 4.25 turns lock-to-lock.

Symptoms of a worn Super Duty steering box

• Free play at the steering wheel, most noticeable around straight-ahead at highway speed
• Drifting or floaty steering that needs constant correction, worse with a trailer or a full bed
• A notchy, tight or binding spot when turning, or effort that is heavier one direction than the other
• Grinding or clunking felt through the wheel that is not coming from the front suspension
• Fluid weeping from the sector shaft seal under the box or from the input shaft seal at the top

How to confirm the box before you buy

Do a dry-park check with the engine running and the truck on the ground. Have a helper rock the steering wheel a few inches each way while you watch the input shaft and the pitman arm. If the input shaft turns and the pitman arm sits still for part of that motion, the slack is inside the box. If the pitman arm moves right away, follow the motion outward: drag link ends, tie rod ends, ball joints and the track bar wear on these trucks too, and replacing the box will not fix a loose joint. Check the pump and fluid as well, since a low reservoir or a whining pump causes hard steering that is not a box fault. A clunk on throttle tip-in is usually driveline, not steering; our 5R110W whine and clunk diagnosis guide helps you separate the two.

Fitment

This listing fits 2008-2010 Ford F-250 and F-350 Super Duty pickups whose steering shaft connects to a double-flat input shaft. The earlier 2005-2008 box uses a 29-spline single-flat input, and trucks with that style need the 2005-2008 Super Duty steering box (ZSG7621) instead. Because both listings cover 2008, look at the input shaft on your old box before ordering. Compare the mounting pattern, line fittings and input shaft on your truck to the photos, or send us your year and VIN and we will check it. For drivetrain parts that fit these trucks, see the 5R110W TorqShift parts collection.

Install notes

• Point the front wheels straight, center the steering wheel and secure it so the clockspring is not wound while the shaft is off.
• Mark the intermediate shaft to the input shaft, then remove the pinch bolt and slide the coupler off. Inspect the coupler and shaft; a loose coupler feels exactly like a worn box.
• Cap the pressure and return lines as you remove them to keep dirt out. Pull the pitman arm with a proper puller, not a hammer, and install it on the new sector shaft aligned on its master splines.
• Torque the frame bolts, pitman nut and pinch bolt to the factory values for your truck.
• Flush out the old fluid, since debris from a failed box will circulate into a new one. A Magnefine magnetic inline filter in the return line catches metal before it reaches the pump.
• Fill with the fluid printed on the reservoir cap or in the owner's manual, raise the front wheels and turn lock-to-lock slowly to purge air, topping off as you go. Do not hold the wheel against the stops.
• Check toe and center the steering wheel afterward, and road test before towing.

If the front end needs ball joints while it is apart, our ball joint and U-joint press kit for Class 1-3 trucks handles heavy-duty truck joints. For towing setups on these trucks, read 5R110W towing upgrades.

Will this steering box fit my 2008 F-250?

It fits 2008-2010 F-250 and F-350 Super Duty trucks that use the double-flat input shaft. The 2005-2008 ZSG7621 box with a 29-spline single-flat input also lists 2008, so check the input shaft on your old box or send us your VIN before ordering.

Is this a rebuilt core or a new unit?

It is new, not rebuilt, and there is no core charge or core return.

Do I need to replace anything else with the steering box?

Inspect the steering shaft coupler, drag link, tie rod ends, ball joints and track bar. Any slack in those parts will still show up as play at the wheel. Replace the old fluid and consider a return-line filter if the old box shed metal.

How do I bleed the power steering after installing the box?

Fill the reservoir with the fluid specified on the cap, raise the front wheels, and turn the steering slowly lock-to-lock several times, first with the engine off and then running, topping off until no bubbles appear. Avoid holding the wheel against the stops.

Should I just tighten the adjuster on my old box instead?

Adjusting a worn box usually tightens it at center while wear elsewhere in the gear stays, which can cause binding and poor return to center. If the box leaks or has internal wear, replacement is the lasting fix.

Will I need an alignment?

Replacing the steering box does not change caster or camber, but check toe and steering wheel centering afterward, especially if any tie rod or drag link parts were replaced.

• 5R110W Noise Diagnosis: Whine and Clunk
• 5R110W Towing Upgrades
• 5R110 TorqShift Service Guide
• 5R110W High-Mileage Service Checklist