Yukon Gear 1541H Alloy Left Hand Rear Axle For Ford 9in (66-75 Bronco)

If your 1966-1975 Ford Bronco has a Ford 9-inch rear end and the driver side shaft is twisted, bent, chewed at the splines or simply worn out at the bearing journal, this is the direct replacement. Yukon YA F900014 is a new left hand rear shaft made from 1541H alloy, with 28 splines, a 5-lug flange and an overall length of 26-15/16 inches, built for the 11 x 1.75 inch drum brakes the early Bronco used.

What the axle shaft does in a Ford 9-inch

The 9-inch is a drop-out third member design: the gears and carrier unbolt from the front of the housing and there is no rear cover. Each rear shaft slides in from the housing end, its splines engage a side gear in the carrier, and the outer end is held in by a pressed-on wheel bearing, a retaining ring and a retainer plate bolted to the housing flange. That means the shaft does two jobs at once. It carries engine torque to the wheel and it carries the weight of that corner of the Bronco. On a short-wheelbase rig that has been lifted and put on bigger tires, the left shaft takes a beating every time the truck is launched or bounced off a ledge.

Symptoms of a failing left rear shaft

• One wheel stops driving with an open differential while the driveshaft still turns: the classic broken-shaft or stripped-spline sign.
• A clunk on takeoff or when you get on and off the throttle, from splines that have twisted or worn loose in the side gear.
• A wobble in the left rear wheel or a drum that pulses, caused by a bent shaft or flange.
• Growl from the left rear that changes with speed, often a worn bearing journal or a bearing that was reused one time too many.
• Gear oil on the brake shoes or backing plate, which points at the axle seal and often a scored seal surface on the old shaft.

These trucks predate on-board diagnostics, so there are no trouble codes to read. Diagnosis is hands-on.

How to confirm it before you buy

Jack the left rear up, pull the drum and put a dial indicator on the axle flange; more than a few thousandths of runout as you turn it means the shaft or flange is bent. Then remove the four retainer plate nuts, slide the shaft out and look at the splines and bearing area under good light. Our Ford 9-inch problems and rebuild cost guide walks through the other failures that sound like a bad shaft, including worn carrier and pinion bearings, so you do not replace the wrong part.

Fitment

Yukon lists this shaft for the 1966-1974 Ford Bronco and the 1975 Bronco 4WD with a Ford 9-inch, 28-spline rear. Not every early Bronco left the factory with a 9-inch rear, so first confirm the housing has no rear cover and the third member bolts in from the front. Count the splines on your old shaft (28) and measure it end to end; this part is 26-15/16 inches and is left side only, because the right side shaft on these trucks is a different length. If you are running a 31 or 35-spline locker or a different brake package, this shaft is not the right match. Send us your year and VIN if anything does not line up. Later trucks with a 9-inch should look at the Yukon 1541H 9-inch rear axle for 1977 and later.

Install notes

• The wheel bearing and its retaining ring have to be pressed onto the new shaft with a hydraulic press. Never reuse the old retaining ring, and never heat it with a torch to get it on.
• Fit a new axle seal and check that the retainer plate and its studs are straight before you bolt it up.
• Fill with 75W-90 or 85W-140 gear oil to the bottom of the fill plug. If the carrier has a clutch-type limited slip, add friction modifier.
• If the gears howl or the side gear splines are worn, now is the time for the Yukon Ford 9-inch master overhaul kit (LM102910 small-bearing third members). For better traction on 28-spline shafts, the Detroit Truetrac 28-spline 9-inch drops in without changing shafts.

Not sure what else your 9-inch needs? Browse all of our driveline hard parts.

Will this shaft fit the right side of my early Bronco?

No. YA F900014 is the left hand shaft at 26-15/16 inches. The right side on an early Bronco 9-inch is a different length and needs its own shaft.

Does it come with the wheel bearing installed?

Yukon's description covers the shaft itself, with no bearing, seal or retaining ring listed. Plan on pressing a new bearing and a new retaining ring onto it.

My Bronco has a 31-spline locker. Will this work?

No. This shaft has 28 splines and only fits a 28-spline side gear. A 31 or 35-spline carrier needs matching shafts.

What brakes does it work with?

Yukon specifies it for use with the 11 x 1.75 inch drum brakes used on these Broncos. If you have converted to discs, check that the flange and bearing location match your bracket kit before you order.

What gear oil should I use after the swap?

75W-90 or 85W-140 gear oil, filled to the bottom of the fill plug, with friction modifier added only if the carrier is a clutch-type limited slip.