Folk, I am trying to determine which oil weight and how much to add to my Cat D4D with a manual transmission. I see posted online SAE 30 oil weight along with 85W oil. The SAE 30 seems to thin for a manual trans (seems appropriate to a hydrostatic trans). The SAE 85 seems incorrect as I would expect a multiweight like 85-140 or something of the like.

Additionally, dumb question but is fill on the side of the transmission or top next to the dipstick and shiftlever with a round plug having a hex-female cutout? Trying to prepare myself for how long I might be living under the tractor to change the trans oil since it was white when I checked it yesterday after running the tractor briefly.

Thanks for the help.

I think 80 weight or 90 weight is the weight types you are looking for for the transmission. Its gear oil you are looking for. the 30 weight oil is crankcase oil.

Nowadays, there seems to be oils with ISO numbers. I think the 80 and 90 weight equivalents are something like ISO 160 and ISO 320

If you are in a cold place and will be running the tractor in the winter, it is probably a good idea to go with the lower weight oil. However, if you are in a hot place and it rarely gets freezing, a heavier oil would be better.

Multigrade oil may be a good option if you can find it as it is designed for both winter and summer weather.

caterpillar did indeed recommend 30wt oil for transmissions and still does in some application. you need to make sure the oil you use carry at least cat TO2 but probably that number has been superseded by cat. look at cat oils online for clarification.

Everything on the D4D uses SAE 30. Engine, transmission,bevel gear, flywheel clutch, steering clutches and final drives. Everything but the engine uses TDTO (TO-4 spec).
Both transmission and bevel gear compartments are filled up top by the dip stick. Takes 6 gallons.

Thanks everybody for the feedback on oil weight to use and location to fill.

I think most people use some type gear oil in the finals, I do in my D4D and 955H both about the same age.

Cat has a good 50W gear oil, other brands, Conoco, Phillips probably can match it.

I always heard CAT made the recommendation for 30wt in everything for only a few years before reverting back to recommending gear lubes for gear compartments, especially final drives. Since the bevel gear shares the oil from transmission, I would use a heavier oil there as well. I have used 50 weight motor oil in the transmission of my D69u, but that was mostly because I had a 55 gallon drum of it sitting around, so I changed both engine and transmission oils.

i am interested in the D4D transmission. i understand that the D4D was a much beefier transmission and final drive compared to the earlier D4 series tractors. am i correct in this? also was the D4D manual sliding gear different than the Special Application ag tractors? i wonder if the D4D manual transmission is pressure lubricated?

DD transmission was still splash lubricated.