OEM vs Aftermarket Dishwasher Wash Arm Retainer Nut for Whirlpool: Honest Comparison (9742945)

You're staring at your Whirlpool dishwasher's wash arm spinning loosely — or worse, not spinning at all — because that little retainer nut has cracked. The OEM part from Whirlpool costs $28–$35 depending on where you look. The aftermarket version? $14.99. That's more than a 50% difference for what's essentially a threaded plastic nut.

Let's be honest about what you're actually getting with each option.

Quick Answer

For a wash arm retainer nut, aftermarket makes sense for most people. This isn't a motor or control board — it's a simple threaded retainer that holds the spray arm in place. Both versions use durable plastic that handles hot water and detergent exposure. Unless you're fixing a dishwasher under manufacturer warranty (where OEM is required), save the $15–$20.

Side-by-Side Comparison

When OEM Makes Sense

There are exactly three situations where paying double for the OEM retainer nut is justified:

You're still under manufacturer warranty. If your Whirlpool dishwasher is less than a year old and this part failed, use the OEM part. Mixing aftermarket parts can void coverage on related components, and you'll want that protection on big-ticket items like the pump or control board.

You're a landlord managing rental properties. Some property management companies require OEM parts for liability reasons or to maintain bulk service contracts with authorized repair networks. The price difference gets absorbed into operating costs.

You're reselling the appliance immediately. If you're flipping a dishwasher or prepping a rental unit for sale, having all OEM parts can be a selling point to picky buyers who check part numbers.

When Aftermarket Wins

For everyone else — and that's most DIY repairs — the aftermarket version delivers identical performance at half the cost.

It's the same functional design. Both nuts thread onto the pump housing shaft and lock the wash arm assembly in place. There's no electronic component here, no calibrated spring tension, no bearing surface that wears differently. It's a threaded retainer. The aftermarket version matches OEM thread pitch and diameter precisely.

The material handles the environment equally well. High-impact plastic rated for dishwasher use means it survives 140°F+ water temps, aggressive detergents, and thousands of wash cycles. Both versions use similar polymer compounds — often from the same raw material suppliers.

You actually get better warranty coverage. Heima backs this part for 365 days versus the typical 90-day OEM warranty. If the threads strip or the nut cracks within a year, you're covered. That's confidence in the manufacturing quality.

It's in stock and ships faster. OEM parts often require dealer orders that take 5–7 business days. Aftermarket parts ship from warehouse inventory in 2–3 days. When your dishes are piling up, that matters.

Our Verdict

Go aftermarket unless warranty compliance requires otherwise. You're saving $15–$20 on a part that performs identically to OEM, ships faster, and carries longer warranty protection. This is exactly the kind of simple mechanical component where aftermarket manufacturers excel — no complex engineering, just precise manufacturing to match original specs. Put that saved money toward a good dishwasher cleaner or save it for when you eventually need to replace the heating element.

Frequently Asked Questions

Will the aftermarket retainer nut fit my KitchenAid dishwasher?

Yes — Whirlpool manufactures KitchenAid, Maytag, Kenmore, and Jenn-Air dishwashers, and they share wash arm assemblies across brands. This retainer nut (part number 9742945, also sold as WP9742945) fits models like DU925SCGB0, DU931SCGQ0, and hundreds of others across all four brands. Check your model number against the compatibility list to confirm.

How do I know if the retainer nut is my actual problem?

If your wash arm spins loosely, wobbles during the cycle, or has come completely off, the retainer nut is either cracked or missing. Remove the lower dish rack and lift out the wash arm — you should see a threaded shaft coming up from the pump housing. If there's no nut threaded onto it, or if the nut has visible cracks around the threading, that's your issue. Sometimes the nut looks fine but the internal threads have stripped, which you'll only discover when it won't tighten properly.

Can I just use a regular hardware store nut as a substitute?

Don't try it. Standard hardware nuts aren't rated for continuous hot water and detergent exposure — they'll corrode or crack within weeks. Dishwasher retainer nuts use specific plastic compounds engineered for that environment. Plus, the thread pitch is often non-standard, so a hardware store nut likely won't even fit properly. At $14.99 for the correct part with a year warranty, it's not worth improvising.