22-74370-000 vs 22-73952-000: WhyCascadia Cab Extender BracketsCome Loose

Summary. The Freightliner Cascadia upper and lower cab extender fairings are held to the sleeper wall by two bracket types of different lengths: the 22-73952-000 attachment arm at 2 3/8 in and the 22-74370-000 extended attachment arm at 4 5/8 in. Both OEM parts are injection molded from 40% glass filled polypropylene and both are fastened into M6 nutserts set in the fiberglass sleeper wall. The failure owners report most often is not a broken bracket. It is the nutsert working loose in the wall until the hole wallows out and the bracket, still intact, comes away with it. This page explains how to tell the two brackets apart, how the joint fails, what a loose extender costs in fuel, how to repair the wall before replacing the brackets, and where the 22-73952-000BP and 22-74370-000BP fit in that repair.

Bushido Performance manufactures the 22-73952-000BP and 22-74370-000BP. The findings on this page are drawn from owner reports, the molded markings on the OEM parts, bench measurements and published fuel economy guidance, and inference is identified as such throughout. Bushido Performance is not affiliated with Freightliner or Daimler Truck North America.

Which bracket is which

The two parts share a VMRS code, a mounting position and much of their OEM description, which is why they are confused in catalogs and at the parts counter. Length settles it. Measured across the flat, the 22-74370-000 is almost exactly twice the length of the 22-73952-000.

Our measurements run about 1/16 in under the published metric figure on both parts. The offset is the same on each, which points to where the tape is laid rather than a difference in the parts. On the extended arm, an OEM 22-74370-000 and our 22-74370-000BP measured the same length side by side on the bench.

What owners report

A 2022 thread in the heavy duty mechanics forum at TruckersReport describes the failure in the owner's own words. The cab extender brackets on a Cascadia sleeper had started to come away from the wall. The brackets were intact. The problem was behind them:

"The hole now has an oblong shape, like the digit 0 rather than the letter o ... The hole is still 10 mm wide but is now taller."

The owner measured the inserts as 10 mm nutserts with M6 threads, 19 mm deep. The replies are consistent with one another. One mechanic wrote that "the material is too thin, nutcerts work good if installed in the proper material". Another wrote that nutserts "rattle out of the fibreglass" and that it is "very common on the Freightliner the past 10 years". A third warned that larger nutserts would help "for a while, until they too get wobbly".

The distinction matters for the repair: when the joint has failed at the wall, a new bracket alone will not hold.

How the joint works loose

The sequence below is our reading of the owner reports and the geometry of the parts. It is not the result of testing.

• The extender is a lever. The cab extender panel is large, light and exposed to the air moving past the sleeper. Every gust and every pass of oncoming traffic pushes it, and the brackets carry that load back to the wall as a small rocking motion at the fastener.
• The fit relaxes. A bracket clamped against the wall only resists rocking while the clamp load holds. Once the fastener has settled or the mating face has worn, the bracket can move slightly under each load cycle instead of staying fixed.
• The movement reaches the nutsert. A nutsert is held by being expanded against the edges of its hole. In a thin fiberglass wall there is little material for it to grip. Small repeated movement works the insert against the edge of the hole, and the hole elongates in the direction of the load.
• The hole grows faster than it looks. An oblong hole lets the insert move further on each cycle, which enlarges the hole further. By the time the bracket visibly sags, the hole is usually past the point where the same size insert will hold.

The practical conclusion is that the bracket and the wall fail together. A loose bracket should prompt a look at the nutserts, and a pulled nutsert should prompt new brackets, because a bracket that has been rocking against a loose joint has worn its own mating face.

What a loose extender costs in fuel

The cab extenders close the space between the back of the sleeper and the front of the trailer. That gap is a known source of drag. Cummins, in its fuel economy guidance for line haul trucks, states two rules that together put a number on it:

• "Beyond approximately 30 inches, every 10-inch increase in tractor-trailer air gap increases aerodynamic drag by approximately 2%."
• "Every 2% reduction in aerodynamic drag results in approximately 1% improvement in fuel economy."

Taken together, each additional 10 in of open gap is worth roughly 1% of fuel economy at highway speed. That figure is our arithmetic from the two Cummins rules, not a test of a loose extender. We have not measured how much a sagging or missing extender opens the gap, and we do not claim a fuel figure for our parts. The point is directional. An extender that is hanging off the wall is no longer doing the job it was fitted for, and the cost of that shows up in fuel rather than in looks.

A five minute check

1. Look along the sleeper. With the truck parked, sight along the side of the sleeper to the extender. It should sit flush and parallel. A trailing edge that stands off the sleeper or droops at the bottom points to the lower mount.
2. Push the panel. Press the lower edge of the extender in and out by hand. A sound mount has almost no free play. A clunk or visible movement at the bracket means the joint has already loosened.
3. Watch the fastener, not the bracket. While moving the panel, watch the bolt head. If the bolt and nutsert move together with the bracket, the insert has lost its grip in the wall.
4. Check every bracket on the fairing. The brackets share the load. One loose bracket means the others have carried the extra movement, and each should be checked before ordering.

Repairing the mount

Repair the wall first and the brackets second. A new bracket fastened into a wallowed hole will loosen again.

• Nutsert still tight, bracket worn or cracked. Replace the bracket and torque the fastener to the factory specification. Replace both lengths together if both show wear.
• Nutsert spinning or loose, hole still round. A new nutsert of the same size can be set in the existing hole. This is the least invasive repair and is only reliable while the hole is undamaged.
• Hole elongated. A larger nutsert is a common field repair. The owners in the thread above expected it to last only until the new hole wore in the same way. The repair they recommended as permanent is a through bolt with a large fender washer and a lock nut on the inside of the sleeper wall, which spreads the load over a wider area of fiberglass. It requires removing the interior trim panel to reach the back of the wall.

We describe these repairs as owners and mechanics report them. Fiberglass repair is outside our scope and a body shop or dealer should be consulted where the wall itself is cracked.

What is molded into the OEM parts

Both OEM brackets carry their own specification. The OEM 22-74370-000 we bought for comparison, shown in Figure 3, is molded 22-74370-000 REV A and >PPGF40<. Product photographs of a new 22-73952-000 at Big Rig World show it molded 22-73952-000 REV B and >PPGF40<. PPGF40 is the ISO marking for polypropylene with 40% glass fill, a standard specification for an injection molded bracket of this kind. The same designation is molded into the Kenworth T680 fairing brackets we cover in our A33-1268 comparison.

Design changes in the 22-73952-000BP and 22-74370-000BP

Our brackets address the bracket side of the joint. They do not repair a damaged wall.

• Thickened mating face. The face that seats against the sleeper wall is built up so the joint takes full clamp load as soon as the fastener is torqued. The aim is to remove the clearance that lets the bracket rock against the nutsert.
• Carbon fiber reinforced plastic. Selected for stiffness and resistance to creep under sustained clamp load, so the seated face holds its shape rather than relaxing over time.
• Factory geometry. Length, hole positions and mounting points match the OEM parts. The 22-74370-000BP was checked against an OEM part on the bench. Both install on the factory mounting points with no drilling.

When the OEM part is the appropriate choice

• The truck is under factory warranty and the repair is being performed by a dealer.
• Fleet or lease requirements specify genuine parts.
• Same day availability is required and a local dealer has the part in stock.

The 22-73952-000BP and 22-74370-000BP are aftermarket parts. Only a part supplied through Freightliner is OEM.

Pricing and availability

Prices checked on 24 September 2026. The Big Rig World shipping figure is the lowest rate offered at checkout for one 22-74370-000 shipped to Texas; rates vary by destination. Bushido Performance ships free within the United States. Both OEM brackets are inexpensive, and the cost of this repair is in the labor and, where the wall is damaged, the nutsert or through bolt repair. Pricing varies by retailer and over time and should be confirmed at the point of purchase.

Methodology and disclosure

Bushido Performance manufactures the 22-73952-000BP and 22-74370-000BP and therefore has a commercial interest in this page. The evidence consists of an owner thread at TruckersReport, quoted without usernames; an OEM 22-74370-000 purchased at retail and photographed in our shop (Figures 2 to 4); the molded markings on a new OEM 22-73952-000 as photographed by Big Rig World; bench measurements of both lengths; and published fuel economy guidance from Cummins. The failure mechanism is our reading of the owner reports and has not been tested. The fuel figure is arithmetic from two published rules and has not been measured on a truck. Neither part has undergone laboratory testing.

Sources

• Owner reports. "Problem: Cab extender brackets coming loose from Freightliner Cascadia sleeper", TruckersReport heavy duty mechanics forum, 28 February to 2 March 2022, accessed 23 September 2026.
• Gap drag and drag to fuel economy. Cummins, Secrets of Better Fuel Economy, pages 3 and 10.
• OEM material, revision and descriptions. 22-74370-000: molding on the OEM part in our shop (Figure 3). 22-73952-000: product photographs at Big Rig World. Listings for 22-73952-000 and 22-74370-000, accessed 23 September 2026.
• OEM pricing. The Big Rig World listings above, accessed 23 September 2026.

Frequently asked questions

What is the difference between 22-74370-000 and 22-73952-000?

Length and position. The 22-73952-000 is the attachment arm, 2 3/8 in long. The 22-74370-000 is the extended attachment arm, 4 5/8 in long. Both mount the upper and lower cab extender fairings on the Freightliner Cascadia, both are 40% glass filled polypropylene, and they are not interchangeable.

Do I need both brackets?

Both fairings use both brackets. A complete set is two 22-74370-000 and three 22-73952-000 for the upper fairing, and four and three for the lower. If one bracket has worked loose, the others have carried the same vibration, and replacing the full set avoids a second teardown. Our cab extender bracket kit comes in upper and lower versions, each a complete set for that fairing: $48 for the upper and $70 for the lower, shipped free.

Why do Cascadia cab extender brackets come loose?

Owners most often report that the M6 nutsert in the fiberglass sleeper wall works loose, and the hole wallows into an oblong shape until the fastener no longer holds. The bracket is frequently intact when it comes away.

Will a new bracket fix a loose cab extender?

Only if the nutsert is still tight in a round hole. If the hole has elongated, the wall has to be repaired first, with a new or larger nutsert or a through bolt with a fender washer and lock nut on the inside of the sleeper wall.

Does a loose cab extender affect fuel economy?

Cummins guidance puts about 2% aerodynamic drag on every 10 in of tractor trailer gap beyond 30 in, and about 1% fuel economy on every 2% of drag. An extender that no longer closes the gap gives up part of that benefit. We have not measured the effect of a loose extender on a truck.

Which Cascadia models do these fit?

The Freightliner Cascadia PT-126, model years 2018 to 2024. Fitment on other Cascadia models should be confirmed with Bushido Performance before ordering.

What warranty is provided?

The 22-73952-000BP, the 22-74370-000BP and both fairing kits carry a 90 day warranty from delivery covering defects in materials and workmanship. The warranty does not cover damage resulting from improper installation, collision or misuse. Claims require proof of purchase and photographs of the defect.