That's what I'm supposed to put in the final drives of my D6C.

I can't seem to find that type of oil anywhere...

The oil that's in the final drives in not 80 w 90, but it' snot SAE 30 either. Any ideas on where I can get SAE 50? (Other than the CAT dealer $$$)

The finals always called for TO oil so the 80-90 can be used. At the dealer I worked for in your case of the D6C we always used the 90 in them when servicing them in the shop.

"SJ" wrote:

The finals always called for TO oil so the 80-90 can be used. At the dealer I worked for in your case of the D6C we always used the 90 in them when servicing them in the shop.

Can I just top off what is in there with 80w90?

I think I,d drain them both and install all new oil in them and check the drained oil for any metal in it so you can eliminate any future problems.

It has always been an understanding that it is never good to mix different types of gear oil, but here is the good news. If the 80-90W is a GL-5 rated oil it should be compatable with the older oils so you should not have any problems. The older GL-3 and 4 oils were not required to have any compatability requirments with the API and SAE. GL-5 does. SJ has some good advice also! Hope this helps.

Ok, next question, how many 5 gallon buckets of 80w90 do I need to buy to drain & refill the final drives?

Takes an even five gallons each side.

We switched over to non detergent 50W years ago in our finals, with 90 W we were getting about 2 years before rebuilds, since the change 15 - 20 years ago we have more than doubled the service life of the rear end componets.

I started using 50 weight in seventies or eighties- but have used HDX or equivalent. I believe this was at Cat Recomendation, but could have been from shell or combination. This came about when working on an early model 943

The oil type I posted was from some older operators manuals I have here and also what we used at the Cat dealer but been retired going on 17 yrs. now but Cat changes things about as often as I change my under shorts so if you,d check in a late operators manual it should give you what to use now.Maybe Bob or OM might have later books to see what they say now and Bob works at a Cat dealer so chime in Bob when you check it out.