Brakes & Air System

Air supply versus foundation brake

Separate air-supply parts — dryer cartridges and gladhands — from foundation brake parts such as shoes, chambers, slack adjusters, and hub seals before you shop.

Chamber type, slack spline, and shoe width are easy to mismatch across axles that look identical from the catwalk.

Dryer cartridges must match the dryer body family on the truck; AD-IS and AD-9 style bodies are not casual swaps.

• Log pushrod stroke and lining thickness on the work order before parts come off the axle.
• For hub seals, note oil versus grease and inner versus outer so the replacement faces the correct direction.
• Oily purge from a dryer often points upstream at the compressor — not only at the cartridge.
• Uncertain chamber tag? Email support@aonetruckauto.com with the VIN and a photo of the removed hardware.

Bench checks before reorder

Record pushrod travel with brakes released and applied; feel alone is not a compliance record.

Compare the old chamber mounting studs and pushrod length to the tag before ordering a look-alike housing.

Hold the removed shoe lining and slack adjuster until the axle is reassembled and stroked — memory fades by lunch.

Typical tractor axles

These SKUs appear on mixed Freightliner, Peterbilt, Kenworth, Volvo, and Mack air-brake tractors in linehaul and vocational duty.

Heavy shoe kits and Type 30/30 chambers are common on tandem drive axles; gladhands and dryer cartridges turn over on nearly every tractor PM lane.

Card chips suggest where to start; each product page carries the make, model, year, and engine rows we publish for that SKU.

Staying inspection-ready

Air-brake inspection is regulatory as well as mechanical. Adjust and measure rather than guessing by pedal feel.

Replace dryer media when tanks stay wet or on the air-system interval — moist air kills valves downstream.

Our technical guides summarize common workflows; axle and brake OEM manuals govern torque and reline procedures. Read shipping policy for transit expectations and returns and refunds before you open sealed brake hardware.

Number swaps that work

Axle brand crosses are useful; pushrod length and mounting studs still win. Compare the old chamber tag before ordering.

HEAVY TRUCK PARTS, INC. sells these parts under Florida law. Brand names indicate compatibility, not sponsorship.

Parts in this air-brake bay

Individual notes below map to each SKU in this department without repeating card pricing.

370001BC4 is National’s Dynamic Edge hub seal for Class 8 wheel-end service during brake and bearing jobs — browse National Dynamic Edge Wheel Seal 370001BC4 for fitment and checkout.

Bendix 065225 is the desiccant cartridge for AD-IS air dryer service on highway tractors; chassis coverage is listed on Bendix AD-IS Air Dryer Cartridge 065225.

Spin-on desiccant 109994 serves Bendix AD-9 dryer purge maintenance — open Bendix AD-9 Air Dryer Cartridge 109994 for applications and cart controls.

Haldex 40010211 is an ABA automatic slack adjuster for S-cam drum stroke control; verify spline and arm geometry on Haldex Automatic Slack Adjuster 40010211.

Meritor 4707Q is the 16.5 by 7 inch drum brake shoe kit stamped 4707 for Class 8 axles — see Meritor 4707Q Brake Shoe Kit 16.5 x 7 before you pay.

MGM 3030 names a Type 30/30 combination spring brake chamber for service and parking brakes; ordering options are on MGM 30/30 Spring Brake Chamber.

Phillips 12-008 is a service and emergency glad hand coupler set with spare seals for tractor-trailer airlines — details at Phillips Glad Hand Pair Service & Emergency.

These seven listings form the public Brakes and Air System set on this site for the current catalog cycle.

Air brakes multiply small leaks into stopping-distance problems. A dryer that passes oil, a chamber that cages poorly, or a slack that will not hold adjustment belongs on a written defect list until corrected.

Hub seals that drip on the inboard shoe bake lining and create fire risk on long grades. Catch seepage during PM, not after the smell reaches the sleeper.

Gladhand seals are inexpensive insurance against trailer charge problems at the shipper dock. Keep spares with the airline kit in the side box.

Stroke measurement discipline

Automatic slack adjusters should maintain stroke within the range your fleet compliance officer expects. Manual adjusters still appear on older trailers — do not assume every wheel end in the yard is automatic just because the tractor is new.

When one side of a drive axle shows shorter stroke, inspect the cam bushings and S-cam itself before blaming the adjuster. A bent pushrod from curb strikes mimics adjuster failure.

Document lining thickness in thirty-secondths or millimeters the same way every tech in the shop measures. Mixed units on work orders cause purchasing to order the wrong shoe width.

Dry air upstream

AD-IS cartridges integrate with integrated dryer bodies common on late-model tractors; AD-9 spin-ons remain on millions of older frames. Purge valve noise changes when desiccant is oil-fouled — listen during the post-trip walk-around.

Replace gladhand grommets when the latch feels loose even if the seal looks intact. Vibration works the rubber out before a leak shows at the gauge.

Wheel-end coordination

National 370001BC4 hub seals belong in the same conversation as brake reline jobs. Opening the hub for bearings without planning seal replacement invites repeat leaks on the inboard shoe.

Meritor 4707Q shoe kits include hardware many shops renew anyway — compare the kit contents photo on the product page to your crib stock before midnight orders.

MGM 3030 chambers appear on countless drive axles; confirm pushrod length and chamber mounting type against the tag before swapping a chamber from a parts truck that looked identical.

Phillips 12-008 gladhands are small dollars compared with a DOT air violation — stock a pair where trailers are dropped and picked daily.

Compliance paperwork

Print the fitment table from the product page and attach it to the work order when an auditor asks why a non-OEM cartridge or shoe kit was installed. Independent sellers like HEAVY TRUCK PARTS, INC. rely on accurate part numbers, not brand loyalty alone.

When multiple axles on one tractor use different chamber tags, label each line on the order — purchasing mistakes on tandem drive sides are expensive comebacks.

Bendix 065225 and 109994 cartridges are not interchangeable — mixing dryer families creates purge faults that waste an afternoon chasing valves.

Haldex 40010211 automatic slacks reduce manual adjustment labor but still need periodic stroke verification — treat them as maintenance items, not lifetime parts.

40010211 and 4707Q often land on the same work order after a drive axle inspection finds both stroke and lining out of spec — order both from the cards above when the evidence supports it.

National 370001BC4 seals deserve a clean hub face and light oil on the lip — scoring the spindle during brake work converts a seal job into a bearing job.