You don’t really say what you have, so I wouldn’t expect too many responses.
I use Lucas 75W – 90 synthetic in my Dana60 front, and my Dana 80 LS (DRW) rear, as well as in my gear vendor OD.
It seems that Ford has changed the specs on the rear dif oil multiple times, but this weight oil has been recommended in the past, and it is what gear vendor calls for now, so I use it in everything. The last time I changed my rear diff oil, it came out so golden and new looking, I had to break out my phone and videotape it as it poured into the waste oil pan.
A forum community dedicated to Ford F-series owners and enthusiasts with a Power Stroke diesel engine. Come join the discussion about performance, bulletproofing, modifications, classifieds, troubleshooting, maintenance, and more!