Description
Hustler OEM 770388 Spindle Assembly Drive Pulley
Keep your Hustler Mower and Mower Deck running Smooth and True with this genuine Hustler OEM 770388 Double Pulley. This Heavy-Duty Pulley is designed Specifically for Hustler Spindle Assemblies to Keep Proper Mower Deck Belt Alignment, Tension, Consistent Blade Drive Performance and to Maintain Proper Mower Deck Speed and Torque Ratio (Due to Proper Manufacturer Size and Weight Specifications). Built to OEM specifications, it ensures correct belt tracking and prevents premature belt wear caused by aftermarket fitment issues.
Note: Review the Diagrams above in the Images or Below in the Descriptions (Below the Model Fit Chart to Gain a Visual Understanding with the Presented Notes When Ordering or Assembling (Especially for Rear Discharge Models)
- OEM Part Number: 770388 - * Part Number 839-189C, 839 189C, 839189C Superseded to Part Number 770388
- Part Name: Mower Deck Spindle Assembly Double Drive Pulley (7")
- Application: Mower Deck Belt & Spindle Assembly System
- Genuine Hustler OEM: Correct fit, balance, and belt alignment
Fits These Hustler Models/Families
Verify your Model Number in the Model Fit Chart Below and Refer to Diagrams in the Images Above to Ensure a Correct Fit Before Ordering.
- Super Z & Super Z HD (2011 - Current 60" REAR DISCHARGE MODELS) * Used only on the Center Spindle Assembly.
- Super 88 (CENTER MOWER DECKS ONLY) * Right & Left Mower Deck Wing Spindles Uses a Single Pulley.
- Diesel Z (2018 - 2024 72" REAR DISCHARGE MODELS ONLY) * Used only on the Center Spindle Assembly.
- Bac-Vac Kit (Select 72" Bac-Vac Require a Double Pulley Replacement with the Single Pulley on the Discharge-Side Spindle - To Enable an Additional Belt to be ran to the Blower Housing)
Part Function & Usage
The 770388 pulley plays a critical role in the mower’s belt-driven system. It is used to:
- Maintain proper belt wrap around blade spindles
- Control belt tension and prevent slippage
- Guide belt routing to maintain cutting efficiency
- Reduce vibration through balanced rotation
- Allows Mower Deck to Operate at Proper Speed and Torque Ratio with OEM Sized Idler Pulleys - Per Manufacture Specifications
Assembly & Installation Direction
- Disconnect spark plug and remove key before servicing.
- Lower deck to lowest position and relieve belt tension using the idler tensioner.
- Note belt routing carefully before removal (take a picture if needed).
- Rotate spindle assembly and wiggle pulley to determine if spindle assembly bearings are rough, worn, and have excessive play - if so, replace before installing the new pulley (refer to spindle assembly 607407P for Spindle Assembly replacement or help links in rebuilding the spindle assembly).
- Remove retaining bolt and washer securing pulley to the spindle assembly.
- Install new pulley with factory spacer orientation intact.
- Ensure pulley groove faces the belt correctly (belt rides fully inside V-groove).
- Reinstall bolt using manufacturer torque specification (70 ft-lbs. or 95Nm).
- Reinstall belt and confirm correct routing on all spindles and guides.
- Rotate deck by hand to confirm proper tracking before starting engine.
Note: Refer to the Images Below and Additional Note and Common Parts Reference for Additional Information.
Installation Tips from the Shop
- If the belt shows glazing or cracking, replace it at the same time.
- Check all spindle assemblies & idler pulleys for rough bearings while belt is removed.
- Inspect spindle pulley grooves for wear that may cause belt jump-off.
- Always verify spacer placement — forgotten spacer placement can cause belt misalignment.
- After installation, run mower briefly and recheck belt tracking.
REAR DISCHARGE NOTES
Model Fit Chart
Super Z & Super Z HD
(2011 - Current 60" Rear Discharge Only)
930024, 932053, 932178, 934216, 934307, 934935, 935023, 936914, 937011, 940031, 941195, 941245, 941559, 942862, 943035, 943910, 944025
Super 88
936617, 939546
Diesel Z
(2018 - 2024 72" Rear Discharge Only)
938266US, 940486US, 943266US
Select BAC-VAC Kits
No Listed Model Numbers & Diagrams
ASSOCIATED PARTS DIAGRAMS
Not sure if this is the correct pulley?
Contact us with your Hustler model and serial number and our parts team will verify fitment before you order.