Usage:
There are three types of crankshaft seals used on 3400 Series Truck Engines. This article explains how each seal works and where the seals are to be used.
Front (2W1733) And Rear (2W1734) Hydrodynamic Crankshaft Seal Groups
Reference: Service Magazine, November 1, 1982, Page 4, "New Crankshaft Seal Groups Used " and March 11, 1985, Page 3, "New Crankshaft Seal Groups Used On More 3400 Series Engines ".
Cross section of hydrodynamic seal.
These seals have hydrodynamic grooves in their sealing lips. These grooves move lubrication oil back into the engine crankcase as the crankshaft turns. Because this type of seal is directional, the front seal is different from the rear seal. If a seal is used on the wrong end of the crankshaft, lubrication oil will flow out of the engine because the grooves in the seal are in the wrong direction in relation to the crankshaft rotation. These seals replace the former 7N1999 Crankshaft Seal Group in most 3400 Series Truck Engines.
Single Lip Silicone Rubber (7W6130) Crankshaft Seal Group
This seal has a single silicon rubber sealing lip. It replaces the former 7N1999 Crankshaft Seal Group in some 3400 Series Engines.
Cross section of single lip seal.
Double Lip Silicon Rubber (5N5987) Crankshaft Seal Group
Reference: Service Magazine, May 23, 1983, Page 3, "Double Lip Crankshaft Seal Helps Stop Oil Leakage ".
This seal has a double silicon rubber sealing lip. It is designed for use in 3412 Marine Engines used with 7231 Marine Transmissions. The seal prevents the transfer of transmission oil into the engine.
Cross section of double lip seal.
Seal Usage
Chart A shows the correct usage of each of the crankshaft seal groups either by engine model or machine model number. The footnotes and Chart B contain exceptions to Chart A.
Modification Of Front Housing
A 2W1733 Crankshaft Seal Group can be used if the front housing is modified as follows.
The existing bore diameter in the front housing for the seal is 186.093 ±0.038 mm (7.3265±.0015"). The front housing can be modified by boring the seal bore completely through to a diameter of 186.144 ±0.038 mm (7.3285±.0015").
NOTE: On modified front housings only, use 6V1541 Quick Cure Primer to clean the bore in the housing and put 9S3265 Retaining Compound on the outside diameter of the seal before installation.
Seal Installation
Special Instructions SMHS7100 and SMHS8508 have installation information and a list of the tools needed to install crankshaft seals in 3400 Series Truck Engines.