Cat 12e grader transmission oil

Hi all, I am a newbie here but I am in awe of the knowledge some of you blokes have stored up about old cat stuff.

I have just got my hands on a 1965 12e grader that is hopefully going to be pulling its weight around the farm pretty soon, before it does this I would like to change all the fluids in it. I have already done the coolant and the engine oil shouldnt be too much of an issue but could someone tell me the right grade of oil to go in the transmission and tandem drives please? The serial number is 21f1077 if that is any use.


The 12e seems like a good machine and to my surprise almost everything works fine apart from being a little rough on some of the dog clutches and a bit loose in the steering.

Thanks in advance

steve

Op and Maint manual (Form 33489-3, 99E1 and up) calls for 26 quarts of 30 wt in the tranny, also there's a filter just to the side and a little further to the rear of the park brake drum. Cat may have changed the specs for oil in later critters (mine is a 1960 model 99 E 1035) so someone else may chip in with updated info on this.

Happen to have the service manual open for a little later model (1970's) and everything gear and drive train used SAE 90 gear oil except the steering gear housing used SAE 30 lube oil and hydraulics was SAE 10W.
I expect yours would be the same.

Current lube designations have all changed now and here is a viscosity chart to help compare.

Thanks a lot for the info, the bit of digging I have done has turned up answers from 50w to 85w140 so I am still a bit confused, but I think I am going to settle for 80w90 and go for it. On another subject I was pleasantly surprised at the price of a filter set for that machine. 2 engine oil, 1 transmission, 1 hydraulic and 1 fuel filter plus all gaskets needed came to a total of around $100, I was quite happy with that.

Have a nice day

steve