GT41857 2-Pack Output Axle Seal for Ariens & Husqvarna Tractors Review: The $7 Fix for a Leaking Transmission
There’s a particular kind of frustration only a riding mower owner knows — you’re halfway through mowing, and you spot a dark, greasy stain spreading across the garage floor. Your transmission is leaking. Left alone, that leak can destroy a hydrostatic transmission worth hundreds of dollars. The GT41857 2-Pack Output Axle Seal is a low-cost replacement part designed to stop that leak before it becomes a five-figure repair bill — well, a four-figure regret. Our GT41857 output axle seal guide covers fitment details in depth.
If you’re shopping around for related Husqvarna gear, our 10m power cable for Husqvarna Automower puts this pick in context.
2Pack Output Axle Seal GT41857 21549029
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Quick Verdict
The GT41857 2-Pack Output Axle Seal is a smart buy for DIY mower owners facing a transmission or axle grease leak on Husqvarna, Ariens, Craftsman, or Poulan riders equipped with the RS800 hydrostatic transmission. At roughly $7 for two seals, it costs a fraction of a dealer repair ($100–$200+ with labor), and the nitrile rubber (NBR) construction is the industry-correct material for petroleum-based hydraulic fluid. The two-pack matches best practice — replace both axle seals at once, since the second one usually fails soon after the first. It’s not an OEM-branded part and requires correct measurement and careful installation, but for the price, it’s one of the highest-value repairs you can make to a riding tractor.
What Is the GT41857 Output Axle Seal?
The GT41857 2-Pack Output Axle Seal is a two-piece replacement seal kit for the output axle of the RS800 hydrostatic transmission — the transaxle widely used across Husqvarna’s riding mower lineup and shared by many Craftsman and Ariens models. Each seal carries multiple cross-reference part numbers: GT41857, 21549029, 587086401, and 590100301, which is why it fits such a broad range of machines.
According to the manufacturer, the seals are made from acrylonitrile-butadiene copolymer — better known as NBR or nitrile rubber. That material choice matters. An output axle seal lives in a hostile environment of constant friction, heat, and hydraulic fluid exposure, and NBR is the industry standard precisely because of its excellent oil resistance, abrasion resistance, and heat tolerance. This is not a generic one-size-fits-all rubber ring; it’s the right compound for the job.
Who is this for? Anyone who owns an RS800-equipped rider from Husqvarna, Craftsman, Ariens, or Poulan and has noticed grease or transmission fluid weeping around the axle. If you’re comfortable pulling the rear wheels and prying out an old seal, this kit turns a dealer visit into an afternoon project.
Key Specs at a Glance
| Specification | Detail |
|---|---|
| Part Numbers (Cross-Reference) | GT41857, 21549029, 587086401, 590100301 |
| Quantity | 2 seals per pack |
| Material | Nitrile rubber / NBR (acrylonitrile-butadiene copolymer) |
| Primary Application | RS800 hydrostatic transmission output axle |
| Compatible Brands | Husqvarna, Craftsman, Ariens, Poulan |
| Known Fitments | Husqvarna GT87070, GT87069; RS800 variants 582491201, 590277701, 590277601, 590277501; Craftsman 917203900/911/901, 917250810/811/821/820/842/841, 917203921; Ariens 936048–936089 series |
| Approximate Price | ~$7 for the two-pack |
Always verify your mower’s model and serial number against the fitment list (or measure the old seal) before ordering — cross-reference numbers are your best friend here.
Pros: Why This Seal Kit Is Worth Considering
1. Exceptional Value for Money
Let’s address the elephant in the room. At roughly $7 for a two-pack, this is an extraordinarily affordable repair. A repair shop transmission seal job can easily run $100–$200 or more once labor is factored in, and OEM seals ordered through a Husqvarna or Ariens dealer typically cost significantly more per seal. For homeowners and independent operators who wrench on their own equipment, this price point makes the repair almost a no-brainer.
2. The Two-Pack Matches Best Practice
Axle seals come in pairs — one on each side of the transmission. When one fails, the other has endured identical heat, wear, and fluid exposure and is usually not far behind. Replacing both at once is standard practice, and this kit includes both seals in a single purchase. No half-finished job waiting on a second order.
3. The Right Material for the Job
Nitrile rubber (NBR) is the go-to sealing material for hydraulic and transmission applications because it resists petroleum-based fluids, tolerates heat, and maintains a tight seal under pressure. This isn’t bargain-bin silicone that will swell and degrade in transmission fluid — it’s the correct compound.
4. Broad Cross-Brand Compatibility
Thanks to its four cross-reference part numbers, this seal set covers a wide swath of machines: Husqvarna GT87070 and GT87069 riders plus multiple RS800 transmission variants (582491201, 590277701, 590277601, 590277501); a long list of Craftsman models (917203900, 917203911, 917203901, 917203921, and the 917250810 through 917250842 series); and numerous Ariens tractors (936048, 936049, 936073–936077, 936083–936086, 936089, and more). One part number in your search bar, and odds are good your machine is covered.
5. Prevents Catastrophic (and Expensive) Damage
A leaking axle seal isn’t just a messy driveway — hydrostatic transmissions rely on fluid for lubrication and hydraulic pressure. Run one low on fluid and you’re shopping for a complete transaxle, which can cost several hundred dollars. A $7 seal set is cheap insurance.
Cons: Where It Falls Short
No part is perfect, and honesty matters when you’re trusting an aftermarket seal with your transmission:
- Aftermarket, not OEM. While the material spec is correct, it isn’t a factory-branded Husqvarna/Ariens part. Fit tolerances can occasionally vary slightly from OEM, so inspect the seal against the old one before installation.
- Verification is on you. With four cross-reference numbers and hundreds of compatible models, it’s essential to confirm your exact model number before ordering. Ordering blind risks a return hassle.
- Installation requires some skill. Seals must be driven in square and to the correct depth without nicking the lip. A rushed install can cause a new leak even with a quality seal. You’ll need basic tools, axle pullers or slide hammers in some cases, and patience.
- No included installation hardware or instructions. It’s seals only — no grease, no guide, no seal driver. Experienced DIYers won’t mind; first-timers should watch a model-specific teardown video first.
Installation Tips for Best Results
- Clean the axle shaft thoroughly and check for burrs or scoring — a damaged shaft will kill a new seal fast. Wrap any keyway or sharp edge with tape when sliding the seal on.
- Lightly coat the seal lip with compatible grease or transmission fluid before installation to protect it during initial run-in.
- Drive the new seal in evenly with a socket or seal driver of matching diameter; it must sit square, not cocked.
- Replace both seals while you’re in there — the two-pack makes this easy and it’s the correct approach.
Frequently Asked Questions
What part numbers does this seal replace?
It cross-references four part numbers: GT41857, 21549029, 587086401, and 590100301. If any of these appear on your old seal or in your parts diagram, this kit should fit.
Will it fit my Husqvarna or Craftsman riding mower?
It’s designed for mowers and tractors using the RS800 hydrostatic transmission, including Husqvarna GT87070/GT87069, numerous Craftsman 917-series models, Ariens 936-series tractors, and Poulan riders sharing the same transaxle. Check your model number against the fitment list or your machine’s parts diagram before ordering.
Why does it come in a two-pack?
Because your transmission has two output axle seals — one per side. When one fails, the other has endured the same wear and is likely near the end of its life too. Replacing both at once is standard practice and saves you a second teardown later.
Is nitrile rubber (NBR) a good seal material?
Yes — it’s the industry standard for hydraulic and transmission seals. NBR offers excellent resistance to petroleum-based fluids, strong abrasion and heat resistance, and good sealing force, which is exactly what a hydrostatic transmission output axle demands.
Can I install these seals myself?
If you can remove a rear wheel, pull an axle, and drive a seal in square, yes — this is a very achievable DIY job. Take your time, protect the seal lip during installation, and check the axle shaft for damage first. If you’re not comfortable with the teardown, a shop will charge $100–$200+, which is worth comparing against your skill level.
How much does this save versus a dealer repair?
A professional transmission seal replacement typically runs $100–$200 or more with labor. At around $7 for two seals, the parts cost is roughly 3–7% of a shop repair — making this one of the best value-per-hour DIY projects on a riding mower.
Final Verdict
The GT41857 2-Pack Output Axle Seal is exactly the kind of part that keeps DIY mower ownership rewarding: correct material, sensible packaging, broad fitment, and a price that borders on trivial compared to the damage it prevents. It demands careful fitment verification and a careful install, but for RS800-equipped Husqvarna, Ariens, Craftsman, and Poulan tractors with a weeping axle, it’s the obvious first move before you spend dealer money. If your garage floor is telling you something, listen — for seven bucks.
