Eaton Fuller Trans

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Mar 30, 2016
Northern Michigan
I am wanting to change the lube in a transmission I am working on. Its a FS-5601a 6 speed in a 1993 topkick. Has a PTO mounted on it. The manual shows different options on what to use to fill it. First it shows the CD50 synthetic transmission fluid. Also shows HDEO 40w and 50w and also GL1 90w gear lube. The synthetic Im sure would work well but is expensive for a truck not used much. The other options seem hard to find around here. I can find 30w and multigrade diesel oils. Do I need to just pay for the synthetic or does anyone know of other options for this tranny?
My recommendation would be the synthetic SAE 50 manual transmission lube. It will be more expensive, but it will also be the last time you should have to replace the lube.
Looking at new class8 trucks, the diffs and trannys have tags saying use syn oils . The engines run conventionals.
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