Yukon Gear 1541H Alloy Rear Axle For Ford 9in (77+)

A 1977-1987 Ford F-150 or a 1977-1986 full-size Bronco with a 9-inch rear end that clunks on takeoff, wobbles a rear wheel, or has one tire that quit pushing is usually telling you an axle shaft is done. Yukon YA F900001 is a new rear shaft for those trucks, made from 1541H alloy with 31 splines, an overall length of 32 inches and a 5-lug flange drilled for the 5 x 5.5 inch bolt pattern. Yukon lists it for both two-wheel drive and four-wheel drive F-150s and for the 4WD Bronco of the same era.

What the rear axle shaft does in a Ford 9-inch

The Ford 9-inch is a semi-floating axle with a drop-out third member, so the ring gear, pinion and carrier come out the front of the housing as one bolted assembly and there is no rear inspection cover. The shafts are not held in by C-clips in the carrier. Each one is retained at the outer end by its wheel bearing, a pressed-on retaining collar and a retainer plate bolted to the housing flange. The inner splines ride in the carrier's side gear. That arrangement means the shaft carries both the torque from the ring gear and the weight of that corner of the truck. On a late-70s F-150 that tows or runs bigger tires, the shaft takes a lot of bending and twisting load, and a 1541H alloy shaft is a stronger replacement than a worn factory piece that has already been through a few bearing jobs.

Symptoms of a bad 9-inch rear axle shaft

• The driveshaft turns but one rear wheel does not drive (with an open carrier): a broken shaft or stripped splines.
• A clunk when you shift into gear or get on and off the throttle, from splines that have twisted or worn loose in the side gear.
• A rear wheel that wobbles or a brake drum that pulses, caused by a bent shaft or flange after an impact.
• A growl or hum that follows road speed, often a failed wheel bearing that has also chewed the bearing journal on the shaft.
• Gear oil on the brake shoes or backing plate, which points at the axle seal and a worn seal surface.

These trucks predate OBD-II, so there are no trouble codes for a shaft problem. Diagnosis is hands-on.

How to confirm it before you buy

Put the rear on stands, pull the drum and set a dial indicator against the axle flange. Runout of more than a few thousandths as you rotate it means a bent shaft. Next remove the four retainer plate nuts, pull the shaft and inspect the splines and the bearing journal. Noise that changes on and off the throttle is a gear or pinion bearing issue, not the shaft, and our Ford 9-inch problems and rebuild cost guide explains how to separate the two. A cracked pinion support or worn carrier bearings are fixed with a Ford 9-inch master overhaul kit for LM501310 bearing centers or the LM603011 large-bearing version, depending on your third member.

Fitment

Yukon's fitment data lists this shaft for the 1977-1986 Ford Bronco 4WD and the 1977-1987 Ford F-150 in both RWD and 4WD, all with the Ford 9-inch rear, 31 splines, 32 inches long and a 5 x 5.5 inch bolt pattern. Ford phased the 9-inch out in favor of the 8.8 in the mid-80s, so a late F-150 may have an 8.8 instead: check that the housing has no rear cover and the center section bolts in from the front before you order. Then count the splines on your old shaft, measure it from the flange face to the spline end, and confirm the lug pattern. A 28-spline axle or a shaft of a different length will not interchange. Earlier Broncos need a different part, such as the Yukon left rear shaft for the 1966-75 Bronco. Send us your year and VIN if anything does not match.

Install notes

• The wheel bearing and the retaining collar must be pressed onto the new shaft with a hydraulic press. Never reuse the old collar, and never heat it with a torch.
• The 9-inch used more than one axle bearing size. Match the bearing to your housing ends; large-bearing housings take the Yukon Set 20 tapered axle bearing and seal kit.
• Fit a new axle seal and check that the retainer plate is flat and the studs are straight before torquing the nuts.
• Refill with 75W-90 or 85W-140 gear oil to the bottom of the fill plug, adding friction modifier only if the carrier is a clutch-type limited slip.
• If you want both tires to pull, the Yukon Grizzly Locker for 31-spline 9-inch axles drops into the same third member.

Browse more driveline hard parts for your 9-inch build.

Does this shaft fit both sides of my 1977-1987 F-150?

Yukon lists one 32 inch shaft for these trucks without naming a side. Measure both of your old shafts before ordering; if your housing uses different lengths left and right, one side needs a different part.

Is the wheel bearing included?

Yukon's product details list the shaft only: 31 spline, 32 inches, 5 lug. Plan on a new axle bearing, retaining collar and seal, pressed on at a shop with a hydraulic press.

My truck has a 28-spline carrier. Will this work?

No. This axle has 31 splines and needs a 31-spline side gear, posi or locker. A 28-spline carrier needs 28-spline shafts.

How do I know my truck has a 9-inch and not an 8.8?

The 9-inch has no bolt-on rear cover; the gears come out the front as a drop-out third member. An 8.8 has a bolted rear cover with the gears inside the housing.

What gear oil goes back in after the job?

75W-90 or 85W-140 gear oil, filled to the bottom of the fill hole. Add friction modifier only for a clutch-type limited slip.