Supplemental Guarantor Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
CASH PROVIDED BY OPERATING ACTIVITIES	$ 194	$ 191
INVESTING ACTIVITIES
Capital expenditures	(63)	(52)
Proceeds from sale of a business	0	4
Proceeds from sale of equity method investment	0	250
Cash paid for investment in Transportation Power, Inc.	(6)	(6)
Cash paid for acquisition of AA Gear & Manufacturing, Inc.	0	(36)
Proceeds from sale of assets		2
Proceeds from settlement of cross-currency swaps	17	0
CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	(52)	162
FINANCING ACTIVITIES
Borrowings and securitization	(46)	(89)
Redemption of notes	(24)	(181)
Deferred issuance costs	(4)	0
Repurchase of common stock	(71)	(63)
Intercompany advances	0	0
Other financing activities	(2)	(3)
CASH USED FOR FINANCING ACTIVITIES	(147)	(336)
EFFECT OF CHANGES IN FOREIGN CURRENCY EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	1	(5)
CHANGE IN CASH AND CASH EQUIVALENTS	(4)	12
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	115	88
CASH AND CASH EQUIVALENTS AT END OF PERIOD	111	100
Elims
Condensed Cash Flow Statements, Captions [Line Items]
CASH PROVIDED BY OPERATING ACTIVITIES	0	0
INVESTING ACTIVITIES
Capital expenditures	0	0
Proceeds from sale of a business		0
Proceeds from sale of equity method investment		0
Cash paid for investment in Transportation Power, Inc.	0	0
Cash paid for acquisition of AA Gear & Manufacturing, Inc.		0
Proceeds from sale of assets		0
Proceeds from settlement of cross-currency swaps	0
CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	0	0
FINANCING ACTIVITIES
Borrowings and securitization	0	0
Redemption of notes	0	0
Deferred issuance costs	0
Repurchase of common stock	0	0
Intercompany advances	0	0
Other financing activities	0	0
CASH USED FOR FINANCING ACTIVITIES	0	0
EFFECT OF CHANGES IN FOREIGN CURRENCY EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	0	0
CHANGE IN CASH AND CASH EQUIVALENTS	0	0
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	0	0
CASH AND CASH EQUIVALENTS AT END OF PERIOD	0	0
Parent | Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
CASH PROVIDED BY OPERATING ACTIVITIES	8	(26)
INVESTING ACTIVITIES
Capital expenditures	(2)	(3)
Proceeds from sale of a business		4
Proceeds from sale of equity method investment		250
Cash paid for investment in Transportation Power, Inc.	(6)	(6)
Cash paid for acquisition of AA Gear & Manufacturing, Inc.		(36)
Proceeds from sale of assets		0
Proceeds from settlement of cross-currency swaps	17
CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	9	209
FINANCING ACTIVITIES
Borrowings and securitization	0	0
Redemption of notes	(24)	(181)
Deferred issuance costs	(4)
Repurchase of common stock	(71)	(63)
Intercompany advances	86	67
Other financing activities	(1)	(1)
CASH USED FOR FINANCING ACTIVITIES	(14)	(178)
EFFECT OF CHANGES IN FOREIGN CURRENCY EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	0	0
CHANGE IN CASH AND CASH EQUIVALENTS	3	5
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	24	10
CASH AND CASH EQUIVALENTS AT END OF PERIOD	27	15
Guarantors | Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
CASH PROVIDED BY OPERATING ACTIVITIES	32	31
INVESTING ACTIVITIES
Capital expenditures	(32)	(25)
Proceeds from sale of a business		0
Proceeds from sale of equity method investment		0
Cash paid for investment in Transportation Power, Inc.	0	0
Cash paid for acquisition of AA Gear & Manufacturing, Inc.		0
Proceeds from sale of assets		0
Proceeds from settlement of cross-currency swaps	0
CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	(32)	(25)
FINANCING ACTIVITIES
Borrowings and securitization	0	0
Redemption of notes	0	0
Deferred issuance costs	0
Repurchase of common stock	0	0
Intercompany advances	0	0
Other financing activities	(1)	(2)
CASH USED FOR FINANCING ACTIVITIES	(1)	(2)
EFFECT OF CHANGES IN FOREIGN CURRENCY EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	0	0
CHANGE IN CASH AND CASH EQUIVALENTS	(1)	4
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	6	3
CASH AND CASH EQUIVALENTS AT END OF PERIOD	5	7
Non- Guarantors | Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
CASH PROVIDED BY OPERATING ACTIVITIES	154	186
INVESTING ACTIVITIES
Capital expenditures	(29)	(24)
Proceeds from sale of a business		0
Proceeds from sale of equity method investment		0
Cash paid for investment in Transportation Power, Inc.	0	0
Cash paid for acquisition of AA Gear & Manufacturing, Inc.		0
Proceeds from sale of assets		2
Proceeds from settlement of cross-currency swaps	0
CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	(29)	(22)
FINANCING ACTIVITIES
Borrowings and securitization	(46)	(89)
Redemption of notes	0	0
Deferred issuance costs	0
Repurchase of common stock	0	0
Intercompany advances	(86)	(67)
Other financing activities	0	0
CASH USED FOR FINANCING ACTIVITIES	(132)	(156)
EFFECT OF CHANGES IN FOREIGN CURRENCY EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	1	(5)
CHANGE IN CASH AND CASH EQUIVALENTS	(6)	3
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	85	75
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 79	$ 78