what fluid for transmission with a fluid drive?

[chrysler1941]

According to both charts, ISO32 is SAE15 and should be a good substitute as no ISO is equivalent of SAE10.

 

In contrast to motor oils, ISO hydraulic oils have 

• Excellent anti-wear properties. 
• Excellent anti-corrosion
• anti-rust properties. 
• Low air retention/air entrainment properties.
• Low foaming properties
• very wide operating temperature range.

[Sniper]

Don't forget that engine oils and gear oils also have different additive packages and as the specifications change, ie GL-1 vs GL-5, so do the additives and in some cases they are not backwards compatible.