Dana 44 Oil Seals

Where Dana 44 seals live

A Dana 44 axle has several seals that keep gear oil in and dirt out. The pinion seal sits where the drive shaft yoke enters the differential housing. Axle shaft seals are at the ends of the axle tubes, and on front axles there are inner axle seals at the differential and, depending on the design, wheel bearing or knuckle seals. A leak at any of them can lead to oil on brakes, low fluid and eventually worn bearings or gears.

Signs a seal needs replacement

• Wet or oily buildup around the pinion yoke or differential cover.
• Gear oil on the inside of a wheel, brake drum or rotor.
• A low differential fluid level, or a burnt smell from brakes.
• Noise from a dry pinion or axle bearing.

Matching the right seal

Dana 44 axles vary by vehicle, year and front or rear position, and the seals vary as well. Sample listings mention dimensions such as outside and inside diameters, spline counts for axle shafts and whether the part is for a Dana 30, Dana 44 or Model 20 axle. Compare the exact measurements, seal location and driver or passenger side. Aftermarket axle housings and tube kits, such as RockJock or Tera series, may use different seals from the factory design.

Installation notes

Seal work calls for proper driving tools so the seal seats square and not damaged. Clean the bore, apply the recommended sealant or lubricant, and inspect the mating surface on the yoke or shaft for grooves. A worn yoke surface can wear through a new seal quickly. After replacing a pinion seal, mark and torque the pinion nut to the manufacturer's specification, since an incorrect preload damages bearings.

After the job, refill with the gear oil grade the manufacturer recommends and recheck for leaks. If the work involves brakes or axle bearings, brake safety applies, so consider professional help. Confirm fitment for your exact axle, year, make and model.

Because seals are inexpensive compared with the damage a leak can cause, many mechanics replace them whenever the axle is opened for bearing, gear or locker work. Keep the vent tube clear, since a plugged axle vent builds pressure that pushes oil past good seals.

Measuring and confirming the size

Seal fit comes down to three measurements: outside diameter, inside diameter and width. A caliper gives much better results than a ruler. Compare the old seal and the new one side by side before installing, and check the lip direction, since a seal installed backward leaks right away. Part number cross-checks are helpful, but axle variations make visual confirmation worthwhile. Listing details such as 2.625-inch outside diameter for an inner axle seal show how specific the sizes are.

Materials and construction

Oil seals have a metal case, a rubber outer surface that seals the bore, and a flexible lip that rides on the shaft, often held by a garter spring. Common lip materials include nitrile, which is general-purpose, and higher-temperature compounds for heavy-duty use. A dust lip on some designs keeps outside grit away. Wheel bearing seals on the outer axle ends also keep grease in the hub and gear oil out of the brakes.

Mistakes to avoid

Do not use a hammer directly on the seal, because it can bend the case. Avoid scoring the shaft or yoke while removing the old seal. Do not overfill the axle, which raises pressure. Replace crush sleeves or shims where the manufacturer requires it.