Need to replace rear main seal

[Space Ace]

94 Chevy fullsize Blazer 4x4 with 6.5 diesel turbo. I need to replace the rear main seal. Any advice on this job??

[03chevy]

Follow the service manual procedure since some manufacturers require the seal to be installed onto the crankshaft prior to installing the crankshaft into the engine, while others install the seal after the crankshaft is installed into the block.
Most seals can be replaced with the engine in the car; others require that the engine be disassembled in order to replace them.

• Unbolt the transmission from the engine. Use a floor jack to support the transmission.
• Prepare the engine for lifting by a cherry picker or other hoist.
• Remove the motor mounts.
• Lift the engine slightly. Use jackstands or a floor jack to support the engine.
• Remove the flywheel.
• Remove the old seal.

There are two types of rear seals: the neoprene lip seal and rope seal.

Rope Seal Almost all earlier engines used another type of rear seal, called the rope, or wick, seal.
Although it was commonly recommended in the past, Fel-Pro Inc. recommends that these seals not be soaked in oil before installation. Soaking of the wick can cause it to disintegrate. Soaking of the wick can cause it to disintegrate, and some of the seal's graphite impregnation might be lost.
To replace the seal:

• Remove the old rope seal with a threaded puller.
• Pound the new seal into place with a special tool or a very large socket.
• It is easiest to shape the seal in the channel in the block, and then remove it and install it in the channel in the main cap.
• Then, use a sharp razor blade type of knife to trim the seal flush with the block.
• Lightly lubricate the seal with chassis grease to avoid damage from a dry start up.

Rope rear seal installation: (a) Install the seal. (b) Form the seal from the channel to the block. (c) Trim the seal. Courtesy of Fel-Pro Incorporated.

• A special tool kit is required to install a split rope seal with the engine in the car. Use a "Chinese finger" to pull the new seal around the crankshaft.
• Complete the installation procedure.

Rope rear seal replacement. (a) A tool kit for rope seal replacement. (b) A threaded tool helps to remove the old seal. (c) A new seal is installed. (d) A "Chinese finger" pulls out the seal. Courtesy of K-D Tools.

NOTE

A conversion from a rope to a lip seal is often possible. Some rope seals have a sharp pin in the main cap to keep them from turning. This pin must be knocked out with a punch if a lip seal is to be used.

Neoprene Lip Seal The most common rear seal is the neoprene lip seal.

• Some of these seals are split in half, and others are a single piece.
• A two-piece seal is tapped around the top of the crankshaft. It is pulled out with a pair of needle nose pliers.
• The split seal should be installed with its parting line offset, and with its lip facing toward the seal.

Neoprene rear seal installation. Courtesy of Ford Motor Company.

NOTE

Be sure to lubricate all neoprene seals with grease during assembly. When the engine is started for the first time, there is a short interval before the seal gets any oil; greasing the seal will protect it from failure during this interval.

• Single-piece neoprene seals have become popular in recent years. Manufacturers can reduce engine weight and length by not having a separate flywheel flange at the rear of the crankshaft.
• A one-piece seal can sometimes be pried out with a screwdriver, or sheet metal screws can be screwed into it to pull it out.

(a) Removing a lip seal with the crank in the block - courtesy of Chevrolet. (b) Pull the seal out with needle nose pliers - courtesy of Chevrolet. (c) A one piece seal can be removed by screwing sheet metal into it - courtesy of Ford Motor Company.

• Single-piece seals are installed in the same manner as the timing cover seal. Use a seal driver or press of the proper size to install the seal.
• Some one-piece rear main seals use a silicone coating on the outer shell. Do not apply oil to the shell for aid during installation; use soapy water. The oil may not be compatible with the silicone.

NOTE

If the seal is installed too tightly, heat can cause the rear main bearing to seize. The seizure will occur on the rear part of the bearing.
After replacing the rope or lip seal.

• Install the flywheel.
  • Flywheel bolts on some of these engines protrude into the crankcase. Sealer must be applied to them to prevent oil leakage from the interior of the oil pan to the clutch surface.

NOTE

Care must be taken that flywheel bolts are carefully torqued, or the crankcase rear main seal surface can become distorted, causing a leak.

• Drop the engine back into place. Keep the hoist in place.
• Loosely install the motor mounts.
• Install the transmission.
• Tighten the motor mount bolts to the specified torque and remove the hoist.