What are you going to do with this truck now?
At first I am going to do a full service to it, and then work it.I am trying to figure out the older fluids that the service manual calls for, before I work it, I will change all the oils and do a full tune up. After that, I will be using it to haul gravel for a lot of landscaping, haul hay, and I have a 1/4 mile driveway that needs a lot of attention. As I work it, I will be fixing it up. Eventually I'd like to do a full restoration, if I can find the parts.
That was pre synthetic era so the trans and diff would have been 90W conventional oil and the engine likely 30W maybe 10w30.
The new synthetic gear oil won't bother the diff but the synchros in the trans might might cause a fuss unless you use the stuff with the friction modifier in it.
Nothing wrong with conventional gear oil if you are concerned about compatibility, especially given the intended use
For the engine, 15w40 Rotella, Mobil Delvac etc will do the trick.
Kevin
