Hi Jonathan, welcome to Outdoorking.

The answer to your question depends on which transmission you have. It seems there were two or three different hydrostatic transmissions used, and prescribed fluid depends on which one your is. It it the same as the one in this illustration?

[Linked Image]

Meanwhile, you can get Eaton's general statement on hydraulic fluid requirements here:
http://www.pirate4x4.com/tech/billa...0Hydraulic%20fluid%20recommendations.pdf

Essentially, they are recommending a hydraulic oil, which typically has SAE20 viscosity. They also say you can use engine oil (not multigrade unless you want to have to change it more often) with an API rating but "hydraulic oil" is preferred because it has extra wear resistant additives. A number of aftermarket publications are recommending SAE30 oil. Presumably either approach will work, but only if you monitor the oil closely and replace it fairly often. Incidentally, are you sure it doesn't need to be replaced now?


Last edited by grumpy; 16/01/15 12:45 AM. Reason: Add detail