Exhibit 99.1 Allison Transmission Announces First Quarter 2024 Results * Record net sales of $789 million * Diluted EPS of $1.90, which includes $0.13 impact from $14 Million of Non-Recurring UAW Contract Signing Incentives incurred in the quarter * Refinanced Revolving Credit Facility and Term Loan, Paying Down $101 Million of Outstanding Debt INDIANAPOLIS, April 25, 2024 – Allison Transmission Holdings Inc. (NYSE: ALSN), today reported first quarter net sales of $789 million and first quarter diluted EPS ...