Yokomo S4-503R17A 40T Ring Gear for YZ-4S Precision Upgrade  [S4-503R17A]

Yokomo S4-503R17A 40T Ring Gear[Use w/17T D Gear] for YZ-4S Gear diff
Price:
CAD$38.12
Brand:
Yokomo
Model:
S4-503R17A
GTIN:
0639342210398
Condition:
Brand New
Quantity Discount
Unit Price You Save
2 $58.19 each $-40.12 or -53%
3+ $52.36 each $-42.70 or -37%
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Drivetrain upgrade for YZ-4S with Yokomo 40T ring gear

The Yokomo S4-503R17A 40T ring gear is made to raise the consistency of your YZ-4S gear differential. Matched to a 17T drive gear, it helps deliver even power transfer and predictable handling during competitive runs. Machined for reliable service life, this ring gear suits hobbyists who want a robust, accurate replacement part.

Features and compatible chassis

This 40T ring gear fits the YZ-4S platform, including B-YZ4SF, B-YZ4SF2-1, MOR-010, and MOR-020 models. Its exact tooth count supports clean gear engagement with the recommended 17T drive gear, giving stable drivetrain feel and reduced vibration under load.
Remark :
Due to limited stock availability, please notice that some Yokomo items may have to order from the factory and the ready time is around 4-6 weeks. Customer purchases the item is assumed to accept the waiting time which allows us to order directly from the manufacturer if the item is out of our warehouse.

Which YZ-4S models will accept this ring gear?

It is compatible with the YZ-4S family, specifically B-YZ4SF, B-YZ4SF2-1, MOR-010, and MOR-020 chassis. Check your differential housing for the same mounting pattern before fitting.

Can I run a different pinion with this ring gear?

The part is optimised for a 17T drive gear to get the intended mesh and clearances. Using another pinion is possible but expect changes to mesh and may need shims or different bearings.

Any tips for installation and break in?

Clean mating surfaces, verify bearing seating, and set gear mesh carefully. Run a few light sessions to check for noise before full-power use to settle the gears.

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