Recall 13V633 affects 29 2011-2013 Thomas Built Buses Saf-T-Liner C2 school buses for hybrid transmission software. Repair is free at franchised Thomas Built Buses dealer.
Thomas Built Buses is recalling 29 2011-2013 Saf-T-Liner C2 school buses equipped with Eaton hybrid automated transmissions because downshift software can raise engine speed without the driver's input. That unintended acceleration raises crash risk, and the dealer repair will be free once Thomas Built Buses makes it available.
Does this recall apply to your specific vehicle?
The official, free per-VIN recall check is run by NHTSA. Enter your VIN and we'll forward you directly — and add you to a free watchlist so you hear about new recalls for your vehicle.
Check my VIN at NHTSARecallNotify doesn't check your VIN — NHTSA's official tool does. We use your email only to alert you to new recalls.
Watch this vehicle for recalls
Add it to your free watchlist and we will alert you as new federal recalls are posted for your year, make and model. New-recall alerts are rolling out now.
You are on the watchlist.
We will email you as new federal recalls are posted for your vehicle.
What's wrong?
The Eaton hybrid automated transmission on 2011-2013 Thomas Built Buses Saf-T-Liner C2 school buses manages gear changes for the driveline. During a downshift, the transmission selects a lower gear so the bus stays in the correct power range. The control software is supposed to make that change without adding engine speed the driver did not request.
In the affected buses, the software controlling the transmission can raise engine speed during a downshift without input from the driver. That changes how the bus responds during the gear change. Instead of only selecting the lower gear, the system adds engine speed on its own, which can move the bus differently than the driver expects.
There is no warning sign before failure. A driver should not count on a dashboard light, noise, or shift feel to identify the software problem before the transmission behavior occurs.
Who's affected?
Covers the same Saf-T-Liner C2 automatic-transmission issue across the 2011, 2012, and 2013 model years.
| 2013 Thomas Built Buses Saf-T-Liner C2 | automatic transmission |
|---|---|
| 2011 Thomas Built Saf-T-Liner C2 | automatic transmission |
| 2012 Thomas Built Buses Saf-T-Liner C2 | automatic transmission |
| Units affected | 29 |
The year and model narrow the scope, but the VIN decides. Check your VIN to confirm whether your specific bus is included.
What's the safety risk?
An unexpected increase in engine speed can cause unintended acceleration and increase the risk of a crash. If the bus responds differently than expected, keep extra space, use normal braking, and schedule service soon. Repair will be free at any franchised Thomas Built Buses dealer once available.
What should I do?
- Check your VIN to confirm your 2011-2013 Thomas Built Buses Saf-T-Liner C2 is included in this recall.
- Contact a franchised Thomas Built Buses dealer and ask whether the free hybrid transmission software update is open for your bus.
- Bring the owner notice if you have it, and reference recall number 13V633 when you call.
- Schedule the hybrid transmission software update that fixes unintended engine-speed increases during downshifts.
- Drive cautiously until the repair is complete, especially during downshifts.
What happens at the repair
At the dealer, a Thomas Built Buses technician updates the hybrid transmission software that controls downshifts in the Eaton hybrid automated transmission. The update is the repair described for campaign 13V633, and parts and labor are covered under the recall. This section does not show a current remedy status, so confirm repair availability when you schedule service. Once the repair is available for your VIN, the dealer performs the software update free of charge.
Timeline
| December 16, 2013 | NHTSA published the recall |
|---|---|
| February 5, 2014 | Owner notification mailed |
Frequently asked questions
What is recall 13V633?
Recall 13V633 covers 29 2011-2013 Thomas Built Buses Saf-T-Liner C2 school buses with Eaton hybrid automated transmissions. The transmission software can raise engine speed during downshifts without driver input, creating unintended acceleration risk. Dealers will update the hybrid transmission software for free.
What should I do if my 2011-2013 Thomas Built Buses Saf-T-Liner C2 is on this recall?
Check your VIN to confirm your specific bus is included in recall 13V633. If it is included, contact a franchised Thomas Built Buses dealer to schedule the hybrid transmission software update. Reference recall number 13V633 when you call. The repair is free.
Is the recall repair free?
Yes. Federal recall law requires the manufacturer to repair the defect at no cost. For recall 13V633, a franchised Thomas Built Buses dealer will update the hybrid transmission software free of charge.
What is the safety risk in recall 13V633?
The safety risk is unintended acceleration during downshifts. The affected transmission software can raise engine speed without the driver's input, increasing crash risk. If your VIN is included, arrange the free software update before returning the bus to regular service.
When did the recall repair start?
The recall repair began on February 5, 2014. Owners can contact a franchised Thomas Built Buses dealer to schedule the free hybrid transmission software update, or call the manufacturer support line at 1-503-745-6910 for recall 13V633.
More information
| NHTSA campaign page | nhtsa.gov/vehicle-recalls/13V633000 |
|---|---|
| Thomas Built Buses customer service | 1-503-745-6910 |
| NHTSA recall # | 13V633 |
| NHTSA recall # (full) | 13V633000 |
Source documents
-
Download Recall Document (PDF) (PDF) - Download Recall Document (PDF) (PDF)
- Download Owner Notification Letter (PDF)
- Download Owner Notice (PDF)
- Download Quarterly Report (PDF)
- Download Defect / Noncompliance Notice (PDF) (PDF)
- Download Recall Acknowledgement (PDF)
This article is generated from NHTSA's primary recall filings and reviewed against the source on June 2, 2026. RecallNotify does not paraphrase NHTSA's consequence language; that text is reproduced as written above. Editorial standards →