1977 Mack U problems

Verdict · NHTSA data

Limited data — recalls on file

NHTSA has just 0 complaints on file for the 1977 Mack U — too few to judge reliability from owner reports alone — but 8 recall campaigns apply to this year, so any used example should have its VIN checked for completed recall work.

NHTSA complaints

Recalls

Investigations

Crash-involved

Fires reported

Injuries

Deaths

—

NCAP overall

How does 1977 compare to other U years?

U NHTSA complaints by model year, 1977 highlighted. Red bars are years to avoid.

See all U years to avoid →

Does the 1977 Mack U have recalls?

8 NHTSA recall campaigns on file. Recall repairs are free at franchised dealers.

79V133000EngineMay 31, 1979 · 23,000 units

Defect

IN THE EVENT OF TURBOCHARGER COMPRESSOR WHEEL FAILURE, ONE OR MORE OF THE FOUR CAPSCREWS THAT HOLD THE TURBOCHARGER TOGETHER MAY BE STRUCK BY PARTS OF THE COMPRESSOR WHEEL, RESULTING IN THE CAPSCREWS BEING DAMAGED. IF THESE CAPSCREWS ARE DAMAGED TO THE POINT THAT THEY ALLOW THE COMPRESSOR BACK PLATE TO DISLOCATE FROM THE TURBOCHARGER BEARING HOUSING, ENGINE LUBRICATING OIL MAY BE ALLOWED TO ESCAPE UNDER PRESSURE, CONTACTING THE ENGINE EXHAUST MANIFOLD SECTIONS OR TURBOCHARGER TURBINE HOUSING.

Remedy

DEALER WILL INSTALL A SHIELD FOR THE HEADS OF THE FOUR CAPSCREWS, ALONG WITH STRONGER SAE 8 GRADE 8 CAPSCREWS, IF NECESSARY, AT NO COST TO OWNER.

79V082000SteeringApril 3, 1979 · 12,000 units

Defect

AN IMPROPER PINCH BOLT AND NUT MAY HAVE BEEN USED IN THE CLAMPING OF THE STEERING SHAFT TO THE STEERING GEAR INPUT SHAFT. DUE TO CLAMPING FORCE LOADS APPLIED AT THE BOLT, THE NUT COULD YIELD, RESULTING IN LOOSENESS OF THE INPUT SHAFT YOKE. SHOULD THIS CONDITION GO UNNOTICED, SPLINE WEAR COULD CAUSE SHAFT SEPARATION.

Remedy

VEHICLES WILL BE INSPECTED AND, IF NECESSARY, THE CORRECT FASTENERS WILL BE INSTALLED AT NO CHARGE TO OWNER.

79V017000SuspensionJanuary 12, 1979 · 4,000 units

Defect

A CASTING DEFICIENCY EXISTS IN THE LOWER SECTION OF THE CAPS RESULTING IN A REDUCTION IN THE THICKNESS OF THE MATERIAL. FAILURE OF A CAP CAN ALLOW THE END OF THE REAR SPRING TO DETACH FROM THE AXLE HOUSING.

Remedy

DEALER WILL INSPECT AND, IF NECESSARY, REPLACE ANY OF THE SPRING INSULATOR CAPS FOUND TO BE DEFECTIVE. THIS WILL BE DONE AT NO COST TO OWNER.

78V210000BrakesOctober 3, 1978 · 19,370 units

Defect

DELAYS OF UP TO ABOUT 2 SECONDS MAY EXIST IN THE BRAKE APPLICATION TIMES TO THE BRAKES ON THE BOGIE AXLES IN THE PRESENCE OF CERTAIN TYPES OF WHEEL SPEED SENSOR SIGNAL DISCONTINUITIES OR DISTORTIONS THAT MAY OCCUR AS A RESULT OF SENSOR WIRE FAILURE. THIS CONSTITUTES A NON-COMPLIANCE TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 121, "AIR BRAKE SYSTEMS".

Remedy

DEALER WILL INSTALL NEW WHEEL SPEED SENSORS THAT INCORPORATE IMPROVED WIRING AND THE PRESENT BOGIE ANTI-WHEEL LOCK SYSTEM WILL BE CHANGED TO AN AXLE-TO-AXLE SYSTEM FOR IMPROVED RELIABILITY.

78V031000SuspensionFebruary 9, 1978 · 33,000 units

Defect

THE TEE BRACKET, WHICH IS MOUNTED ON THE FRONT AXLE OF THE BOGIE, MAY FAIL DUE TO VIBRATION BROUGHT ON BY ROAD SURFACE IRREGULARITIES. BRACKET FAILURE WOULD LEAVE THE TEE BRACKET UNSUPPORTED AND CAUSE BROKEN HOSE CONNECTOR FITTINGS. THIS WOULD RESULT IN AUTOMATIC APPLICATION OF THE SPRING EMERGENCY BRAKES.

Remedy

THE DEALER WILL REPLACE THE DEFECTIVE BRACKET WITH A REDESIGNED VERSION.

77V205000SuspensionNovember 21, 1977 · 7,400 units

Defect

A DEFICIENCY EXISTS IN THE WELDS SECURING THE REAR SPRING INSULATOR BRACKET TO THE AXLE HOUSING. THIS IS DUE TO IMPROPER POSITIONING OF THE WELD, IN RELATIONSHIP TO THE BRACKET AND AXLE HOUSING. FAILURE OF THE WELDS WOULD CAUSE SEPARATION OF THE SPRING INSULATOR BRACKET AND THE AXLE HOUSING, RESULTING IN IMPROPER ALIGNMENT OF THE AFFECTED AXLE.

Remedy

DEALER WILL REWELD THE INSULATOR SPRING BRACKET AT NO COST TO OWNER.

77V173000EngineOctober 12, 1977 · 48,000 units

Defect

THE FLEX BLADE FANS ON THE INVOLVED VEHICLES MAY DEVELOP CRACKS IN THE LAMINATED STIFFENER AS A RESULT OF FATIGUE DURING OPERATION. IF SUCH A CONDITION EXISTS AND THE CRACKS GO UNDETECTED, CONTINUED OPERATION COULD CAUSE PIECES OF THE STIFFENER TO BREAK OFF.

Remedy

DEALER WILL REPLACE THE ORIGINAL FAN WITH A STEEL FIXED BLADE FAN, FREE OF CHARGE.

77V174000Seat BeltsOctober 12, 1977 · 6,591 units

Defect

THE INVOLVED VEHICLES DO NOT CONFORM TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 209, "SEATBELT ASSEMBLIES". ALTHOUGH THE SEATBELTS IN QUESTION PERFORMED MARGINALLY WITH RESPECT TO THE 5000 LB. LOAD REQUIREMENT, ADDITIONAL TESTING CONFIRMED THAT THE ANCHOR COULD FAIL, ALLOWING EITHER THE ANCHOR TO SLIP OVER THE HOLD-DOWN NUT OR THE ANCHOR TO SEPARATE INTO TWO PIECES.

Remedy

DEALER WILL INSPECT AND, IF NECESSARY, REPLACE SEAT BELT ASSEMBLIES WITHOUT CHARGE TO OWNER.

1977 Mack U — common questions

Is the 1977 Mack U reliable?

The record is thin — 0 NHTSA complaints — so owner-report data can't strongly confirm reliability either way, though 8 recalls should be verified as completed.

Does the 1977 Mack U have recalls?

Yes — NHTSA lists 8 recall campaigns affecting the 1977 Mack U. Recall repairs are free at franchised dealers; check the VIN at nhtsa.gov/recalls to confirm the work was done.

Based on NHTSA ODI data through June 2026. Complaints are consumer-reported and unverified. Updated July 5, 2026.

Compiled by Sharon Ben-Moshe, Founder.

How does 1977 compare to other U years?

Does the 1977 Mack U have recalls?

1977 Mack U — common questions

Is the 1977 Mack U reliable?

Does the 1977 Mack U have recalls?

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