the ax5 would only be on a 4 cylinder, it is small in size as compared to the ax15, and the ax15 will be only on the 4.0 engine.
The ax5 has an internal slave cylinder while the 15 has an external one.
Most likely the ax15 manual transmission
That would be most likely the AX15
With the 4.0L it has the AX15 manual transmission.
Most likely ax15 for the 4.0 and the ax5 for the 2.4
5 speed manual is either an AX5 or AX15 auto is a A-904
4 cylinder- AX5 6 cylinder- AX15
The AX5 and AX15 transmissions use 75W90.
Most commonly it is the ax15 5 speed mated to the 4.0
4 Cyl manual is a AX5 6 Cyl manual is a AX15 Auto is a A904
There are three connections on the AX-15 if those connections are available one 90 jeep then go ahead and swap.
Auto: AW4 manual w/ 4cyl : AX5 manual w/ 6 cyl : AX15
The ax5, AX15 transmissions in a 1990 Wrangler use 80W90 gear oil.