Yukon Gear 1541H Alloy 5 Lug Rear Axle (One Single Shaft) For 99 - 04 8.8in Ford Mustang

Built for the 1999-2004 Ford Mustang with the 8.8 inch solid rear axle, this is the shaft to buy when a launch at the track snaps an axle, a wheel starts walking out of the quarter, or the bearing surface is worn to the point that new seals will not stay dry. Yukon part YA FM4235E is one 1541H alloy shaft with 31 splines, 5 lugs and an overall length of 30-3/4 inches. It is made for cars with ABS: it has the provision for the ABS tone ring, but the ring itself is not included.

What the axle shaft does in a Mustang 8.8

The New Edge Mustang's 8.8 is a C-clip axle. Each shaft's 31 spline inner end drives off a side gear in the Traction-Lok or open carrier, and a C-clip at the tip keeps it in place, with the pinion shaft blocking inward travel. Out at the wheel, the axle runs on a roller bearing pressed into the tube, using the shaft itself as the inner race, and the wheel and rotor bolt to its flange. On ABS cars a toothed tone ring pressed onto the shaft passes the rear wheel speed sensor, so the shaft is also part of the ABS and traction control signal. Ford's 31 spline shaft measures about 1.32 inch in diameter versus 1.29 inch for the 28 spline version, and the 1541H alloy adds strength over the factory carbon steel.

Symptoms of a bad Mustang axle shaft

• Car will not move after a hard launch, or the driveshaft turns with no drive to the wheels: broken shaft or sheared splines.
• Rear tire moving out against the fender, or the rotor rubbing the caliper: broken C-clip or a pinion shaft bolt that has backed out.
• Gear oil on the rear brakes from a leaking axle seal that comes back after replacement: worn seal surface on the shaft.
• Humming from one rear corner that rises with speed: worn bearing and journal.
• ABS or traction control light with a rear wheel speed code after axle work: a damaged, cracked or missing tone ring, or one pressed to the wrong position.

How to confirm it before you buy

Support the car on stands, pull the wheel, caliper and rotor, and check the flange with a dial indicator. Drain the oil and pull the cover, remove the pinion shaft bolt and pinion shaft, push the axle in to free the C-clip, and pull the shaft straight out so the wheel speed sensor is not damaged. Count the splines (this shaft is 31), check the bearing surface for a groove, and inspect the tone ring. While the cover is off, look at the ring gear teeth and the Traction-Lok clutches. If the clutches are worn and the car chatters in tight turns, a Yukon Dura Grip posi for 31 spline 8.8 axles is a direct replacement while everything is apart.

Fitment

Yukon lists YA FM4235E for the 1999-2004 Ford Mustang, rear wheel drive, with the Ford 8.8 inch rear and 31 spline axles, as a single shaft. Two things to check first. The 1999-2004 Mustang Cobra used an independent rear suspension with half shafts, not this solid axle shaft. And this shaft is for the 8.8 found in V8 cars; Ford used the 8.8 in V8 Mustangs, so a V6 car may have a different rear axle. Count the splines on your old shaft and measure from the inner end to the outer edge of the flange; it should be 30-3/4 inches. If your car has been swapped or you are unsure, send us the year and VIN before ordering.

Install notes

• Move your old ABS tone ring to the new shaft, or buy a new one; it does not come with the shaft. Press it to the same position as on the old shaft so the sensor reads correctly.
• Replace the axle bearing and seal. A rear axle bearing puller and seal driver kit pulls the old bearing without damaging the tube.
• Slide the shaft in without dragging it across the seal lip, engage the side gear, fit the C-clip, then pull out to seat it. Reinstall the pinion shaft with a new bolt and thread locker.
• Fill with 75W-140 synthetic gear oil, adding friction modifier for a Traction-Lok. The Yukon Hardcore cover for the 8.8 or a 3.55 gear set are common add-ons for a car getting stronger axles.

Does this include both rear axles?

No. YA FM4235E is one shaft. Order two if you are replacing both sides, which is the norm when upgrading for drag racing.

Does it come with the ABS tone ring?

No. The shaft has the provision for the ABS tone ring but the ring is not included. Press your old ring on, if it is undamaged, or buy a new one.

Will it fit a 1999-2004 Mustang Cobra?

No. The Cobra used independent rear suspension with half shafts. This shaft is for the solid 8.8 rear axle with C-clip shafts.

How do I know I have 31 spline axles?

Count the splines on the shaft you pull out. This shaft is 31 spline and 30-3/4 inches long, and it needs a carrier with 31 spline side gears.

What gear oil should I use?

Use 75W-140 synthetic gear oil. If the car has a Traction-Lok limited slip, add the friction modifier.