Overview
The Crown Automotive 4638904 is an output shaft seal for NP231 transfer cases. It seals the output shaft where it leaves the transfer case, so the NP231 application is the main fitment check for this part.
Part number 4638904 and UPC 848399005431 identify the seal, which Crown lists under Direct Fit.
Key features
- Output shaft seal for the NP231
- Seals the output shaft position in the transfer case
- Identified by part number 4638904
- Direct Fit fitment type
Output seal wear signs
An output shaft seal keeps transfer case fluid inside where the shaft leaves the housing. Over time the lip can harden, crack or wear a groove into the shaft surface, and fluid then seeps along the shaft. Early signs include a damp area on the housing, drips under the transfer case, or a fluid level that drops between services.
Before replacing the seal, check the shaft surface where the lip rides. A grooved or rusted surface can damage a new seal quickly, so clean or repair the surface first. Keep the transfer case at the correct fluid level and use a fluid suited to the unit, since low or contaminated fluid speeds up seal wear.
- Look for damp areas around the output housing
- Inspect the shaft surface for grooves or rust
- Check fluid level after a drive
Specifications
| Brand | Crown Automotive |
|---|---|
| Part number | 4638904 |
| UPC | 848399005431 |
| Component | Output shaft seal |
| Transfer case compatibility | NP231 |
| Fitment type | Direct Fit |
Vehicle fitment
No vehicles are named for this seal. Only the NP231 transfer case is stated, so confirm your transfer case model before ordering.
Confirm your vehicle’s year, model and trim before ordering.
What’s included
The output shaft seal, part number 4638904.
Not included: the output shaft, yoke or flange and other transfer case parts.
