ASE T4 Brakes practice test
The T4 test is dominated by air brakes: compressors and governors, valves, S-cam foundation brakes, slack adjuster stroke, spring brakes, and truck ABS. If you hold a CDL, the system knowledge overlaps — T4 tests it at the technician level. Required for Master Truck status.
On a truck ABS system, what happens when a wheel-speed sensor reports impending wheel lockup during a hard stop?
How the T4 test works
50 scored questions
+ ~10 unscored research questions
75 minutes
computer-based, at a test center
$62 per test
plus one $34 registration fee per order
Valid 5 years
then a shorter recertification test
ASE does not publish one universal passing percentage; the passing standard is set by test. TorquePrep uses 80% as a conservative practice target, not as an official ASE cut score. The certificate is issued once ASE verifies your required work experience.
What the T4 test covers
The official task list for T4 Brakes (Medium-Heavy Truck) breaks down into these content areas — the practice bank above draws from all of them:
- Air supply system — compressor, governor cut-in/cut-out, air dryer, tanks
- Air system valves and circuits — treadle, relay, quick-release, tractor protection
- Foundation brakes — S-cam drum, air disc, linings, drums and rotors
- Slack adjusters — stroke measurement and automatic adjuster operation
- Parking and emergency (spring) brakes
- Antilock brakes and stability control on trucks and trailers
Frequently asked
- How many questions are on the ASE T4 test?
- The T4 test has 50 scored questions plus about 10 unscored research questions, with a 75-minute time limit.
- Does T4 cover hydraulic brakes at all?
- Air brakes dominate, but medium-duty trucks with hydraulic and air-over-hydraulic systems appear on the task list too.
- What air-pressure figures should I know?
- The working ranges from the federal standards: governor cut-out typically around 120–135 psi, low-air warning by 60 psi, spring brakes applying automatically in the 20–45 psi range, and the standard leak-test limits.
Exam length, timing, fees, and content areas checked September 11, 2026 against the official ASE test table and ASE study guides.
Other ASE practice tests
Driving trucks, not just wrenching on them?
HaulSchool has free CDL practice tests — general knowledge, air brakes, and every endorsement — plus plain-English DOT physical guides.
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