Hey Cool
The manual says that S.A.E 90 EP. or S.A.E. 140 E.P. gear oil may be used as a substitute for the factory 9 fluid ounces of a special steering box grease confirming to GMH specification C.G.1.
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It goes on to say that to check the level in the box you should
" remove the steering gear cover LOWER attaching bolt, and with steering gear in the straight ahead position , insert a length of 1/16 dia welding wire through the bolt hole to act as a dipstick. The wire should penetrate approx. 3 & 1/4 in. into the housing. if correct the lubricant level should be 1 & 1/2 in. minimum from bottom of wire "
Brad.