What You're Looking At
This is an automatic slack adjuster, meaning it takes up brake shoe wear on its own so you're not sitting there with a wrench doing manual adjustments every service interval. The 28 spline count and 1-1/2" bore are the common size for a lot of Meritor and similar axle setups, and the 5-1/2" arm length matters just as much as the spline - too short or too long and your pushrod travel geometry is off.
These get used on tandem trailers, some straight trucks, and dolly axles depending on how the shop speced the brakes originally. Don't assume because it's a common size it's automatically right for your rig - pull the old slack adjuster and check the arm length and spline count stamped or cast into it before you order.
Why These Numbers Cross
40020227 and R801076 are the same part under two reference numbers - one's more of a catalog number, the other shows up in some parts books as a superseded or alternate listing. Same physical part, same spec.
F01635 on the OE side and M808027 in aftermarket both interchange because they match the same spline count, bore, and arm length spec - that's what actually determines fit here, not the brand stamped on the housing. Where guys get burned is assuming any 28 spline slack adjuster works because the spline matches but the arm is 5" instead of 5-1/2", or vice versa. That half inch changes your pushrod stroke and can throw off your brake adjustment or trip an ABS/stroke sensor fault if you're running one.
Always confirm off the old part number or your VIN before you order. If the numbers are worn off, measure spline count, shaft diameter, and arm center-to-center length yourself - that's cheaper than sending a wrong part back.
Ordering From PartStop
We're out of Tacoma and keep this one in stock for same-day will-call or local delivery if you're in the yard and need it now. Ship nationwide too if you're not local - most orders go out same day if you call before early afternoon.
Comes with our standard 6+ month warranty. If it turns out the cross doesn't match your application, we'll sort the return - just don't cut the part off the axle before you're sure it's right.
40020227 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 40020227. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| OE | F01635 |
| Aftermarket | M808027 |
Frequently asked questions
Does 40020227 fit my trailer axle?
Depends on the axle manufacturer and how it was speced from the factory. Pull your old slack adjuster and check the spline count, arm length, and bore - if it reads 1-1/2" 28 spline with a 5-1/2" arm, this crosses. If you're not sure, give us your VIN or axle tag info and we'll check it against the OE numbers.
Is this the same as the M808027 aftermarket part?
Same spec - 28 spline, 1-1/2" bore, 5-1/2" arm - so it crosses over. Different manufacturer stamping but the fitment and function match. Still worth confirming against your old part number since slack adjusters look similar across brands but arm length varies.
Can I install this myself or does it need a shop?
Slack adjuster swaps are pretty straightforward mechanically, but you need to set the brake adjustment correctly afterward and make sure the automatic mechanism is engaging right. If you're not familiar with S-cam brake service, have a shop do the install and adjustment check.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.