Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Sales	$ 1,154	$ 983	$ 2,138	$ 1,872
Trade receivables, net	684		684		$ 471
U.S.
Disaggregation of Revenue [Line Items]
Sales	639	514	1,164	994
Canada
Disaggregation of Revenue [Line Items]
Sales	14	14	26	26
Mexico
Disaggregation of Revenue [Line Items]
Sales	60	49	109	90
Total North America
Disaggregation of Revenue [Line Items]
Sales	713	577	1,299	1,110
Sweden
Disaggregation of Revenue [Line Items]
Sales	78	74	154	151
Italy
Disaggregation of Revenue [Line Items]
Sales	74	63	132	121
United Kingdom
Disaggregation of Revenue [Line Items]
Sales	41	39	81	82
Other Europe
Disaggregation of Revenue [Line Items]
Sales	35	38	71	75
Total Europe
Disaggregation of Revenue [Line Items]
Sales	228	214	438	429
Brazil
Disaggregation of Revenue [Line Items]
Sales	100	82	189	138
China
Disaggregation of Revenue [Line Items]
Sales	25	35	51	65
India
Disaggregation of Revenue [Line Items]
Sales	57	50	101	83
Other Asia-Pacific
Disaggregation of Revenue [Line Items]
Sales	31	25	60	47
Commercial Truck
Disaggregation of Revenue [Line Items]
Sales	897	742	1,645	1,402
Commercial Truck | U.S.
Disaggregation of Revenue [Line Items]
Sales	445	337	793	647
Commercial Truck | Canada
Disaggregation of Revenue [Line Items]
Sales	0	0	0	0
Commercial Truck | Mexico
Disaggregation of Revenue [Line Items]
Sales	52	44	95	80
Commercial Truck | Total North America
Disaggregation of Revenue [Line Items]
Sales	497	381	888	727
Commercial Truck | Sweden
Disaggregation of Revenue [Line Items]
Sales	78	74	154	151
Commercial Truck | Italy
Disaggregation of Revenue [Line Items]
Sales	69	58	123	111
Commercial Truck | United Kingdom
Disaggregation of Revenue [Line Items]
Sales	39	36	77	77
Commercial Truck | Other Europe
Disaggregation of Revenue [Line Items]
Sales	1	3	2	5
Commercial Truck | Total Europe
Disaggregation of Revenue [Line Items]
Sales	187	171	356	344
Commercial Truck | Brazil
Disaggregation of Revenue [Line Items]
Sales	100	81	189	137
Commercial Truck | China
Disaggregation of Revenue [Line Items]
Sales	25	34	51	64
Commercial Truck | India
Disaggregation of Revenue [Line Items]
Sales	57	50	101	83
Commercial Truck | Other Asia-Pacific
Disaggregation of Revenue [Line Items]
Sales	31	25	60	47
Aftermarket & Industrial
Disaggregation of Revenue [Line Items]
Sales	257	241	493	470
Aftermarket & Industrial | U.S.
Disaggregation of Revenue [Line Items]
Sales	194	177	371	347
Aftermarket & Industrial | Canada
Disaggregation of Revenue [Line Items]
Sales	14	14	26	26
Aftermarket & Industrial | Mexico
Disaggregation of Revenue [Line Items]
Sales	8	5	14	10
Aftermarket & Industrial | Total North America
Disaggregation of Revenue [Line Items]
Sales	216	196	411	383
Aftermarket & Industrial | Sweden
Disaggregation of Revenue [Line Items]
Sales	0	0	0	0
Aftermarket & Industrial | Italy
Disaggregation of Revenue [Line Items]
Sales	5	5	9	10
Aftermarket & Industrial | United Kingdom
Disaggregation of Revenue [Line Items]
Sales	2	3	4	5
Aftermarket & Industrial | Other Europe
Disaggregation of Revenue [Line Items]
Sales	34	35	69	70
Aftermarket & Industrial | Total Europe
Disaggregation of Revenue [Line Items]
Sales	41	43	82	85
Aftermarket & Industrial | Brazil
Disaggregation of Revenue [Line Items]
Sales	0	1	0	1
Aftermarket & Industrial | China
Disaggregation of Revenue [Line Items]
Sales	0	1	0	1
Aftermarket & Industrial | India
Disaggregation of Revenue [Line Items]
Sales	0	0	0	0
Aftermarket & Industrial | Other Asia-Pacific
Disaggregation of Revenue [Line Items]
Sales	$ 0	$ 0	$ 0	$ 0