The 1983 Service Manual for the D6C 10K7953-up does state 50wt for finals (30SAE for below 32 degrees).
Myself I run "Lubrication Engineers" 5250 ALMAGEAR EP Gear Lubricant in all my finals. Don't believe Cat ever advised a proper lube for this application.
The 5250 is an SAE250 (AGMA 8A) 100 percent highly refined paraffinic base lubricant combined with a synthetic polymer and is specifically designed for large gearboxes that must withstand heavy and/or shock loading.

I use this thing when it's below zero outside. That's why I didn't want to go with 80w90, and wanted to ask...

I'll ask my CAT dealer tomorow, see what they say.

Pretty obvious by Cat specs one weight oil will not meet their criteria for both summer and winter temperatures.......but who actually changes for the season. A reasonable compromise would be the 80w90 wt.

We run the 50W it temps in the 110+ range running 24/7. This was a recomendation made by Holt brothers or Quinn as a result of us switching over to Brand X crawlers because of issues of final and rear end life issues.

We were putting anywhere between 4,000 and 6,000 hrs a year on our crawlers when this recomendation was made in one of the hottest places in the US (Kings & Kern County, CA & Yuma, AZ).

The application I refer to does not come from operating tractors. Comes from operating 100 foot long 500 degree curing ovens 24/7 365 days/yr. Extended overhaul life from one year to five on some really nice 250hp Falk herring bone gear reduction drives. Units were mounted adjacent to the ovens but lived in a hot and fouled with glass fiber environment. Made a believer out of me. Stuff isn't cheap but rebuilding finals is no fun either.

CR-
What do you attribute the increase in service life to? Using a lighter oil in a hotter environment is counter-intuitive, but you are seeing results.

The question is- why?

CS

PS the other question is what are you using a trackloader for, that much?

I use my D6C maybe 250 hours per year...

I asked Bob, he said if I can't find the 50wt, to use theTDTO4 30 I use in the transmission, and put that in the final drives...

So the suggestions are all over the map here, lol.

I am hesitant to make these two statements.
The lighter oil would circulate faster, resulting in - lubrication quicker, and more heat transfer because of the increased circulation. Obviously there are limits 5# just wouldn't work.
Secondly as I remember( and I am not sure how to verify)
back then they used two different viscosity rating systems for gear oil and engine oil - resulting in 90 # being close to 50 # if the same rating system were used- and I am talking st. wt. oils

"OneWelder" wrote:

I am hesitant to make these two statements.
The lighter oil would circulate faster, resulting in - lubrication quicker, and more heat transfer because of the increased circulation. Obviously there are limits 5# just wouldn't work.
Secondly as I remember( and I am not sure how to verify)
back then they used two different viscosity rating systems for gear oil and engine oil - resulting in 90 # being close to 50 # if the same rating system were used- and I am talking st. wt. oils

My Dad found a place that sells 50 wt gear oil. I'm not sure what kind he found, I'll find that out when I get home. Hopefully it's the right kind as it costs $67 for a 5 gallon bucket.

I am not saying to use 50 Wt gear oil-I do not know correct answer on that - we used 50 wt Heavy duty motor oil