Packard Forum Index » Pre-War (1899-1942)

So I've been following the manual and changing fluids on the recommended schedule (oil once/yr or at 1,000 miles). Tranny gets SAE140 from June-Oct and SAE90 the rest of the year.

What about the diff? Does that really need to be changed out each year? As I'm using modern oil (Valvoline 85W90 EP rated gear oil) is an annual change necessary or wasteful? You don't hear of modern rear axles oil ever being changed so is it the case here that the modern Valvoline is "good enough" to last for years back there as it does in modern cars?

What do you guys do?

In the old days gear oils would thicken greatly with use which is why they said to change them in the fall so that they weren't like margarine by the time February rolled around. Occasionally I will get in something that has been inactive since the seventies or so and the gear lubes will come out like tar.
The modern oils don't do that and seem to hold their viscosity pretty much indefinitely. At this point I am doing something on the order of 40,000 miles or ten years on my cars. These gearboxes and axles are all broken in and not shedding metal unless they are already on the edge of failure.

I've used SAE85W-140 extreme pressure gear oil in pre- and postwar differentials for decades. I typically change it every 7-10 years which probably equates to 10,000 miles or so and I suspect even that change interval is overly conservative but I'm just guided by the fact that fresh clean lubricant is inexpensive.

Thanks, good to know!