Hi Mike I haven't welcome you to the forum yet so welcome to our addiction.
I am a big fan of synthetic lubricants and a very big fan of Redline products. I love how they work and what they can do. It is amazing how well this oil works, from reducing gear mesh noises, to ease of shifting when this oil is used. Also from how "thick" the HeavyShok is you will not experience any leaks that others have reported from the ZF with other brands of synthetic oils.
I would recommend that you change the oil in the ZF yearly to.
Jeff
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