Which specification does Automatic transmission fluid (ATF) need for the Citroën GS / GSA GS-X3 (1978–1979)?

Automatic transmission fluid (ATF) for the Citroën GS / GSA GS-X3 (1978–1979): Allison TES 389, Caterpillar TO-2.

Which specification does Axle & differential oil need for the Citroën GS / GSA GS-X3 (1978–1979)?

Axle & differential oil for the Citroën GS / GSA GS-X3 (1978–1979): API GL5, MIL-L 2105 D.

Suitable for Citroën GS / GSA GS-X3 (1978–1979)

For the Citroën GS / GSA GS-X3 (1978–1979), the manufacturer specifies motor oil 10W-30 (API SF), 15W-40 (ACEA A3, ACEA B4, API SF), or 20W-50 (ACEA A3, ACEA B4, API SC).

Fluids and approvals for the Citroën GS / GSA GS-X3 (1978–1979)

Fluid	Requirement
Motor oil	10W-30: API SF15W-40: ACEA A3, ACEA B4, API SF20W-50: ACEA A3, ACEA B4, API SC
Automatic transmission fluid (ATF)	Allison TES 389, Caterpillar TO-2
Axle & differential oil	API GL5, MIL-L 2105 D