Getting ready to change out all the fluids.

Doing the Haldex.

Using Redline MT-90 in front Differential/Bevel Box/Manual Transmission.

Question is, can I use the MT-90 in the rear differential?

Any positives or negatives. Understand that the front needs the GL-4 and Rear can take the GL-5 but is it okay to use left over Gl-4 in it or do I really need the extra additives in a GL-5. Would like to use up fluid I have leftover but not at the expense of having future issues.

Advice appreciated.