Yves, since the part numbers on these are the same (ACDelco 10-4034, GM 88862624) and they're the correct ones, I don't think you need to worry about that GL-5 spec designation. It applies to both products, they're the same, but maybe one vendor didn't think it was important enough to display.
Quote:
EP additives
The main difference between GL-4 and GL-5 gear oils is in the level of extreme-pressure (EP) additives. EP additives effectively protect gears by providing a sacrificial layer on gear surfaces; these additives are essential for protecting gears operating under heavy loads and extreme temperatures. A typical GL-5 gear oil provides about twice as much EP additive in its formulation compared to a GL-4 gear oil.
Where are GL-4 and GL-5 gear oils used?
GL-4 gear oils are typically recommended for spur and helical gears found in manual transmissions and transaxles operating under moderate speeds and loads.
GL-5 gear oils are typically recommended for hypoid gears in automotive axles operating under high-speed, high-load conditions.
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(source:
https://blog.amsoil.com/the-differen...gl-5-gear-oil/)
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