Seal Surface Repair: Seal Replacement Step-By-Step

O ne thing old cars and trucks have is a lot of seals. And, like brakes and oil, these “expendables” wear out and must eventually be replaced.

Replacing the seal is easy: just pound out the old one and carefully press in a new one. But what do you do if the surface that the seal hugs is shot? These surfaces can be pitted from rust, or just plain worn from many millions of rotations being hugged by the seal. Don’t bother replacing the seal unless you do something with the sealing surface — the seal just won’t last.

The “easy fix” is to buy a new part. This is the expensive option, and not so easy if the remaining inventory of new parts vaporized years ago.

Another option is to take the part to a machinist and have the part milled. This is expensive and may lead to inferior future seal performance. Fortunately, there is a quick, easy, and relatively inexpensive way of repairing this. Replacement bearing surfaces, going under market names such as Speedi-Sleeve, will re-face the part and, in most cases, restore the seal to like-new condition.

The example for this article is the rear flange that bolts to the splined transmission output shaft of the M35A2 deuce-and-a-half military vehicle, but also applies to seals on passenger vehicles. The rear flange (or “companion flange”) is what links the transmission output to the short output “jackshaft” leading to the transfer case. A seal on the transmission’s rear bearing cover hugs the flange and keeps transmission gear oil from pouring out the back. This is a common problem that accounts for many of the dark spots under vehicles. Mike the diameter of the old flange and purchase a Speedi-Sleeve size that accepts this diameter

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(Figure 1. Most bearing specialty shops carry this repair part, priced in the neighborhood of $35.)

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Figure 2 shows the flange (taken off the truck) with evident wear on the sealing surface.

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The Speedi-Sleeve is positioned over the flange, as shown in Figure 3. A cap that comes with the Speedi-Seal is then placed over the Speedi-Seal.

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The Speedi-Seal is then gently hammered into place with a mallet or large hammer. Figure 4 shows the new surface in place with the hammer cap still on.

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The finished product is shown in Figure 5. Note that the flared ring is still on the surface. It can be left on or snipped and uncoiled off if it gets in the way.

Some people recommend putting the flange in the freezer before pounding on the new surface to make installation easier. As a final step, oil the surface before mating it to the new seal.

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