Recall 19V831 covers 30 2018-2020 Thomas Built Buses Saf-T-Liner Hdx buses for loose torque-converter fasteners. Repair is free at any franchised Thomas Built Buses dealer.
Thomas Built Buses is recalling 30 2018-2020 Saf-T-Liner Hdx school buses because Flex-Plate and torque converter fasteners were not tightened enough. Loose bolts can lodge in the starter and disable the bus, which can require an evacuation in uncontrolled traffic and increase injury risk; Thomas Built Buses dealers will complete the recall repair free of charge.
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What's wrong?
The flex plate and torque converter sit between the Detroit DD8 engine and the Allison automatic transmission on 2018-2020 Thomas Built Buses Saf-T-Liner Hdx school buses. The flex plate connects engine rotation to the torque converter, and the torque converter sends that power into the transmission so the bus moves smoothly from a stop.
On affected buses, the fasteners that hold the flex plate and torque converter together were not tightened to the required torque at the plant. Loose fasteners can back out or break inside the flywheel housing. Once that joint loosens, the engine and transmission connection is no longer held as designed, which can create abnormal vibration or driveline noise and requires dealer inspection.
The warning sign listed for this recall is illumination of the check engine light. If that light comes on, the bus should be checked promptly because loose bolts are the known issue behind this recall.
Who's affected?
Covers the 2018, 2019, and 2020 Saf-T-Liner Hdx model years, all tied to the automatic transmission.
| 2020 Thomas Built Buses Saf-T-Liner Hdx | automatic transmission |
|---|---|
| 2018 Thomas Built Buses Saf-T-Liner Hdx | automatic transmission |
| 2019 Thomas Built Buses Saf-T-Liner Hdx | automatic transmission |
| Units affected | 30 |
| Field incidents | NHTSA has logged no field incidents to date. |
A matching year and model does not guarantee inclusion. Check your VIN to confirm whether your specific bus is included.
What's the safety risk?
Loose bolts can lodge in the starter and disable the bus. If that happens in traffic, passengers can need evacuation in an uncontrolled traffic situation, increasing the risk of injury. A check engine light is the warning sign to take seriously and schedule service promptly. Repair is free at any franchised Thomas Built Buses dealer.
What should I do?
- Check your VIN to confirm your 2018-2020 Thomas Built Buses Saf-T-Liner Hdx is included in this recall.
- Contact your nearest franchised Thomas Built Buses dealer to schedule the free fastener inspection and tightening that keeps loose flex-plate and torque-converter bolts out of the starter.
- Bring the recall notice if Thomas Built Buses mailed one. If not, reference recall number 19V831 when you call.
- Keep the bus out of passenger service if it becomes disabled; arrange service instead of returning it to traffic.
What happens at the repair
At the dealer, a Thomas Built Buses technician inspects the flex-plate and torque converter fasteners and tightens any fasteners that were not tightened enough. The recall repair is free, with parts and labor covered. Because this remedy is available, the service desk can confirm the recall by VIN and schedule the inspection and tightening work for affected Saf-T-Liner Hdx buses.
Timeline
| November 19, 2019 | NHTSA published the recall |
|---|---|
| January 17, 2020 | Dealer notification began |
| January 17, 2020 | Dealer notification ended |
| January 17, 2020 | Interim owner notification (was planned for this date) |
| August 7, 2020 | Owner notification mailed |
Frequently asked questions
What is recall 19V831?
Recall 19V831 covers 30 2018-2020 Thomas Built Buses Saf-T-Liner Hdx school buses with Detroit DD8 engines and Allison transmissions. The flex-plate or torque converter fasteners were not tightened enough. Thomas Built Buses dealers will inspect and tighten the fasteners for free.
What should I do if my 2018-2020 Thomas Built Buses Saf-T-Liner Hdx is on this recall?
Check your VIN to confirm your specific school bus is included in recall 19V831. If it is, contact a franchised Thomas Built Buses dealer to schedule the fastener inspection and tightening. Reference recall number 19V831 when you call. The repair is free.
Is the recall repair free?
Yes. Federal recall law requires the manufacturer to repair this defect at no cost. A franchised Thomas Built Buses dealer will inspect the flex-plate or torque converter fasteners and tighten them as needed, free of charge.
What is the safety risk?
Loose fasteners can lodge in the starter and disable the school bus. If that happens in traffic, passengers can need an evacuation in an uncontrolled traffic situation, which raises injury risk. Confirm the VIN and arrange the free dealer repair.
When did the repair become available?
The recall repair began August 7, 2020. Thomas Built Buses issued an interim owner notice on December 13, 2019, then opened the dealer repair. Owners can contact Thomas Built Buses customer service at 1-800-547-0712 or call a franchised dealer with recall number 19V831.
More information
| NHTSA campaign page | nhtsa.gov/vehicle-recalls/19V831000 |
|---|---|
| Thomas Built Buses customer service | 1-800-547-0712 |
| NHTSA recall # | 19V831 |
| NHTSA recall # (full) | 19V831000 |
Source documents
-
Download Recall Document (PDF) (PDF) - Download Quarterly Report (PDF)
- Download Misc. Document (PDF)
- Download Recall Document (PDF) (PDF)
- Download Owner Notification Letter (PDF)
- Download Owner Notice (PDF)
- Download Recall Report (PDF)
- Download Recall Acknowledgement (PDF)
This article is generated from NHTSA's primary recall filings and reviewed against the source on May 24, 2026. RecallNotify does not paraphrase NHTSA's consequence language; that text is reproduced as written above. Editorial standards →