RESTRUCTURING COSTS - Restructuring Expense Recognized By Segment (Details) - USD ($)	3 Months Ended							12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 10,000,000	$ 1,000,000	$ 1,000,000	$ 0	$ 3,000,000	$ 1,000,000	$ 2,000,000	$ 8,000,000	$ 6,000,000	$ 6,000,000
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs								0	1,000,000	0
Commercial Truck
Restructuring Cost and Reserve [Line Items]
Restructuring costs								3,000,000	1,000,000	2,000,000
Aftermarket, Industrial and Trailer
Restructuring Cost and Reserve [Line Items]
Restructuring costs								5,000,000	4,000,000	4,000,000
Global Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring costs	3,000,000							7,000,000
Global Restructuring Program | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs								0
Global Restructuring Program | Commercial Truck
Restructuring Cost and Reserve [Line Items]
Restructuring costs	4,000,000							4,000,000
Global Restructuring Program | Aftermarket, Industrial and Trailer
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 3,000,000							3,000,000
AxleTech
Restructuring Cost and Reserve [Line Items]
Restructuring costs								3,000,000
AxleTech | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs								0
AxleTech | Commercial Truck
Restructuring Cost and Reserve [Line Items]
Restructuring costs								0
AxleTech | Aftermarket, Industrial and Trailer
Restructuring Cost and Reserve [Line Items]
Restructuring costs								3,000,000
Segment Realignment Program
Restructuring Cost and Reserve [Line Items]
Restructuring costs									3,000,000
Segment Realignment Program | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs									0
Segment Realignment Program | Commercial Truck
Restructuring Cost and Reserve [Line Items]
Restructuring costs									0
Segment Realignment Program | Aftermarket, Industrial and Trailer
Restructuring Cost and Reserve [Line Items]
Restructuring costs									3,000,000
Aftermarket actions
Restructuring Cost and Reserve [Line Items]
Restructuring costs										4,000,000
Aftermarket actions | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs										0
Aftermarket actions | Commercial Truck
Restructuring Cost and Reserve [Line Items]
Restructuring costs										0
Aftermarket actions | Aftermarket, Industrial and Trailer
Restructuring Cost and Reserve [Line Items]
Restructuring costs										4,000,000	$ 5,000,000
Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs								(2,000,000)	3,000,000	2,000,000
Other | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs								0	1,000,000	0
Other | Commercial Truck
Restructuring Cost and Reserve [Line Items]
Restructuring costs								(1,000,000)	1,000,000	2,000,000
Other | Aftermarket, Industrial and Trailer
Restructuring Cost and Reserve [Line Items]
Restructuring costs								$ (1,000,000)	$ 1,000,000	$ 0