A Guide to the Transmission Filter Kit for the 2001-2009 Workhorse W22
Understanding the two-filter system on your Allison 1000 transmission is the key to a long service life.
- Your W22 has two transmission filters: an easy-to-change external spin-on and an internal pan filter.
- Always clean and reuse the donut-shaped magnet from the external filter; it is essential for catching metal debris.
- For this heavy-duty Allison transmission, using a high-quality OEM (Allison) or premium aftermarket (Wix) filter is strongly recommended.
- Regularly inspect your transmission cooler lines for rubbing against the frame to prevent a sudden and catastrophic fluid leak.
Understanding the Two-Filter System
Unlike a typical passenger car, the Allison 1000 transmission in your Workhorse W22 uses two filters. It's critical to know which is which and when to service them.
- External Spin-On Filter: This is a small canister-style filter located on the driver's side of the transmission. It is easy to access and should be changed frequently. Allison recommends changing it at shorter intervals, such as every 12,000 to 15,000 miles, to ensure maximum protection.
- Internal Pan Filter: This filter is located inside the transmission fluid pan and requires removing the pan to access it. It is typically changed less often, during a full transmission service when the fluid and pan gasket are replaced.
Don't Forget the Magnet!
The external spin-on filter has a round, donut-shaped magnet that sits on top of it. This magnet traps fine metallic particles. You MUST remove this magnet from your old filter, clean it thoroughly, and place it on the new filter before installation. If it is missing, you need to purchase a replacement (Allison P/N 29535617).
Symptoms of a Failing Transmission Filter
A clogged filter restricts fluid flow, which can lead to serious transmission problems. Watch for these warning signs:
- Whining or Whirring Noises: Sounds from the transmission that change with engine RPM can indicate the pump is straining for fluid.
- Delayed or Harsh Shifting: If the transmission hesitates to go into gear or shifts are no longer smooth, it could be a fluid pressure issue caused by a clogged filter.
- Burning Smell: A burnt toast or acrid chemical smell can mean the transmission fluid is overheating, a condition made worse by poor circulation.
- Fluid Leaks: While a filter itself might leak, also check your transmission cooler lines. On W22 chassis, these lines are known to sometimes rub against the frame, which can cause a leak and lead to catastrophic transmission failure if not caught early.
Choosing the Right Aftermarket Filter Kit
For a critical component like the Allison transmission, filter quality is not the place to cut corners. The cost of a quality filter is tiny compared to a transmission repair.
OEM/Premium Tier:
- Allison: The original equipment filter (P/N 29539579 for the external filter) is the gold standard and often reasonably priced. It's the safest choice for guaranteed fit and performance. Note that due to supply, the filter may be painted red or black.
- Wix: Wix has a strong reputation for quality in the filtration industry. They offer kits for the W22 (like P/N 58970) and are a trusted alternative to OEM.
Mid/Budget Tier:
- ATP & Premium Guard: These brands are widely available and offer a more budget-friendly option. While some owners use them without issue, for a heavy-duty application like a W22 motorhome, investing in a premium filter from Allison or Wix provides greater peace of mind.
Vehicle-Specific Issues: Recalls and Maintenance Checks
While there are no recalls specifically for the Allison transmission filter on the W22, the chassis itself has been subject to important safety recalls. These include issues with Bosch brake calipers and a fuel rail clip. It is also highly recommended that you inspect the transmission cooler lines for any signs of rubbing against the vehicle's frame, as this is a known potential failure point.
| Item | Estimated Cost |
|---|---|
| New Aftermarket Filter Kit (Internal & External) | $38.13 - $130.49 |
| OEM Allison External Spin-On Filter | $15 - $30 |
| OEM Allison Internal Filter Kit | $70 - $95 |
| Shop Labor (External Filter Change) | $40 - $80 |
| Shop Labor (Internal & External Filter Change) | $150 - $250 |
Frequently Asked Questions (FAQ)
How often should I change the transmission filters on my W22?
Change the external spin-on filter frequently, about every 12,000-15,000 miles or annually. The internal filter can be changed during a full fluid service, typically every 30,000 to 50,000 miles, depending on use.
Do I need to replace both filters at the same time?
No. The external filter is designed for more frequent changes. You can replace it multiple times before needing to service the internal filter, which requires dropping the transmission pan.
What kind of transmission fluid should I use?
You must use a fluid that meets Allison's specifications. A full synthetic fluid like Castrol TranSynd 668 or another Allison-approved TES 668 fluid is the recommended choice for long life and best performance.
Is changing the transmission filter a DIY job?
Changing the external spin-on filter is a simple DIY task, similar to an oil change. Replacing the internal filter is more involved as it requires safely lifting the vehicle, draining the fluid, and dropping the heavy transmission pan. This is best left to experienced DIYers or a professional shop.
Technical Specifications
OEM Part Numbers: 29539579 (External Filter) W8833058 (Internal Filter Kit) 29535617 (External Filter Magnet)
Designed for the Allison 1000 & 2000 Series automatic transmissions found in 2001-2009 Workhorse W22 chassis.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Workhorse W22: