2025 Blue Bird Vision School Bus TSBs

Condition:Chassis web fractures in or around the vicinity of the LF shock mount Root Cause Identification and Justification: FEA modeling shows elevated regions of stress in proximity of the upper fastener hole for the LH shock mount resulting from several external influences. The highest stress stemming from shock extension forces in curb hop scenarios. Bearing in mind the absence of this failure mode on standard floor chassis designs with substantially higher usage, the projected stress in this region of 4582 PSI is used as an objective bench mark of the acceptable upper limit. Two corrective solutions are being executed as pragmatic countermeasures to correct this failure mode, based on the severity and frequency of the crack, if present. Repair plate 1 being the latest evolution. FEA analysis & ref chart below Installation of this repair plate decreases the stress in this region to less than the standard floor chassis baseline allowing us to predict this solution to last the expected life of the chassis.

gasket used to seal off the transmission cooler. This deformation is caused from transmission oil wicking through the thread adapter threads and exposing the lower portion of the gasket to transmission oil. Re-configure hydraulic interface between the transmission cooler lines and the transmission oil cooler. SU2302 Revised to include Labor Time of 1 Hour and a Component Code. Incorrect wording on the Header Page beginning on Page 2.

gasket used to seal off the transmission cooler. This deformation is caused from transmission oil wicking through the thread adapter threads and exposing the lower portion of the gasket to transmission oil. Re-configure hydraulic interface between the transmission cooler lines and the transmission oil cooler. SU2302 Revised to include Labor Time of 1 Hour and a Component Code.

seal off the transmission cooler. This deformation is caused from transmission oil wicking through the thread adapter threads and exposing the lower portion of the gasket to transmission oil. Re-configure hydraulic interface between the transmission cooler lines and the transmission oil cooler.

A software update is required in-person at an authorized Allison Transmission Dealer.

Primary failure seen is deterioration of the EPDM gasket sealing the transmission oil cooler (TOC) to lower radiator tank, which allows a path for coolant to leak externally. Secondary failure seen is cross contamination between coolant and transmission oil. To eliminate the possibility of experiencing this condition, Blue Bird is providing 1 year of coverage to update the transmission oil cooler interface along with a visual inspection of any cross contamination at time of completing the interface update. Please follow the flowchart within the instructions to determine if any additional repair activity is necessary and, if so, complete further repair procedures as stated.

Action: Outline in the SM2401 Service Memorandum Instructions, per SM2401 Flowchart.

limitations of the mechanical switch. As a result, a preventative maintenance adjustment procedure is necessary and, at times, settings can be difficult to achieve.