Hydro-Gear Oil Seal for BDA, BDP-10A, PE, PG, PJ & PK Series Pumps — Replaces 51161 and 50735

Product Details

This Hydro-Gear oil seal is a replacement seal for compatible BDA, BDP-10A, PE, PG, PJ, and PK series pumps used in hydrostatic transmission systems. It is intended for pump service and repair applications where the original seal has worn, leaked, or been removed during disassembly.

The seal is listed as a replacement for Hydro-Gear part numbers 51161 and 50735. Always compare the original seal, pump model, and part number before ordering because other Hydro-Gear pump models may use different seal specifications.

• Replacement oil seal for compatible Hydro-Gear pump applications
• Listed for BDA, BDP-10A, PE, PG, PJ, and PK series pumps
• Suitable for hydrostatic transmission pump service and repair
• Sold as one individual oil seal

Part Number Matrix

Use the following references to help compare this replacement with the seal being removed from your pump.

Pump Compatibility

This replacement is listed for the following Hydro-Gear pump series. Equipment brands and applications can vary, so confirm the pump series and original seal reference rather than relying only on the vehicle or mower brand.

These pump series may be installed in equipment sold under brands such as MTD, Cub Cadet, MTD Pro, Troy-Bilt, Bolens, Craftsman, and White Outdoors. Equipment-brand compatibility is not universal; the Hydro-Gear pump series and original seal reference must match.

Technical Specs

Product Type

Oil seal

Application

Hydrostatic transmission pump service

Compatible Pump Series

BDA, BDP-10A, PE, PG, PJ, and PK

Replacement References

Hydro-Gear 51161 and 50735

Quantity

One seal

What's in the Box

• 1 × Oil Seal

Installation Notes

1. Drain hydraulic fluid as required by the equipment service procedure and relieve system pressure before beginning work.
2. Remove the pump assembly or access the seal according to the equipment manufacturer's service instructions.
3. Carefully remove the old seal without damaging the shaft, housing bore, or surrounding components.
4. Clean the seal bore and shaft with a lint-free cloth and an appropriate cleaning solvent.
5. Inspect the shaft and bore for scoring, pitting, corrosion, or excessive wear. Damaged surfaces may cause a new seal to leak.
6. Lightly lubricate the sealing lip with clean hydraulic fluid recommended for the system.
7. Install the seal in the same orientation as the original seal, with the sealing lip facing the fluid side.
8. Press the seal evenly into the bore using a suitable seal driver or correctly sized installation tool.
9. Reassemble the pump, refill with the manufacturer's recommended fluid, and bleed air from the system as directed by the service manual.
10. Operate the equipment at low speed first and inspect the seal area for leaks before returning the unit to service.

Troubleshooting & FAQ

How do I know if the oil seal needs replacement?

Common signs include hydraulic fluid around the pump shaft or seal housing, continued leakage after cleaning, and transmission-fluid loss. Inspect the shaft and housing as well, because wear or damage in those areas can also cause leakage.

Can I reuse the old seal if it looks intact?

Reusing a removed oil seal is not recommended. Removal can deform the sealing lip or damage the sealing surface, even when no damage is immediately visible. Install a new seal during pump service.

What happens if the seal is installed backward?

The seal may leak if its sealing lip is not oriented correctly. Match the orientation of the original seal and follow the pump or equipment service manual before pressing the replacement into place.

Do I need sealant or adhesive?

Do not apply sealant or adhesive unless the applicable service manual specifically calls for it. Use only the recommended lubricant on the sealing lip and install the seal evenly.

Will this seal fit every Hydro-Gear pump?

No. This listing is for the BDA, BDP-10A, PE, PG, PJ, and PK series applications identified above. Other Hydro-Gear pumps may use different seals. Verify the pump series and original part number before ordering.

How often should the oil seal be replaced?

Replace the seal when it leaks, becomes damaged, or whenever the pump is disassembled and the seal has been removed. Regular inspection is appropriate for equipment used frequently or in demanding conditions.

Is this an OEM part?

This listing is for an aftermarket replacement oil seal, not a Hydro-Gear-branded OEM component. The listed replacement references are provided for identification and cross-reference purposes.

What is included with the order?

The package contains one individual oil seal. It does not include a pump, hydraulic fluid, installation tools, or other transmission components.

Safety & Important Information

• Verify the pump series, original seal, and replacement reference before ordering.
• Do not rely on equipment brand alone to determine compatibility.
• Relieve hydraulic pressure and follow the applicable service manual before disassembly.
• Inspect the shaft and seal bore before installation; worn or damaged surfaces may require additional repair.
• Professional installation is recommended when servicing a hydrostatic transmission pump.

About Sea Sierra

• Pro-Grade Standards — We supply replacement parts selected for practical repair and maintenance applications.
• Global Fulfillment — Shipping options and delivery estimates are shown at checkout based on destination and service availability.
• Manufacturer-Direct Value — We focus on dependable replacement parts and clear compatibility information.