Cat D6C Final Drive Oil

Mcrafty1 · Aug 18, 2022

I'm going to change the gear oil in my final drives, Since the tractor is 55 years old and of the age when gear wear in cat finals was known to be a problem I will be going with a heavy an oil as available...the machine is only used in warm weather so a GL-5 140 looks to be a good fit. Can anyone in the know confirm that? Is there a reason to NOT use this oil? Thanks in advance.

Nige · Aug 18, 2022

I think it's a matter of personal preference, but personally I would vote against it. IMHO a 140 is too heavy.
Logic says the "heaviest oil you can find must be the best", but what happens to an oil that is so heavy that it cannot flow to where it needs to be in the finals before the machine warms up to normal operating temperature and causes problems due to lack of lubrication.? In that respect a heavier oil is a negative.
I would suggest an SAE90 gear oil would be fine for your type of operation.

Mcrafty1 · Aug 18, 2022

Thanks Nige, the fact that the finals on these old machines had thin wear surfaces on the gears I assumed the heavier oil would help aleaviate the slap when changing direction and slow the wear of the surfaces some. The oil that I drained looked free of metal particles and the magnetic plugs had very little metal sludge and no pieces so I suppose I'm looking for a solution without a problem.

John C. · Aug 18, 2022

I seem to recall that 50 weight engine oil was called for in Cat dozer finals. Isn't the viscosity of that somewhere around the same as a 90wt? I'm can't remember if the outboard support bearing on those were greased or ran in oil. I didn't see wear a being an issue on the old tractors. It was generally that things just broke inside there and we considered that a function of the operator or type of operation the machine was used in.

Congratulations on keeping that machine running.

D5Dan · Aug 18, 2022

Hey Mcrafty, as I’m sure you’ve done, I looked thru several HEF projects/recommendation posts, then on my 67/68 D5 I used Tractor Supply 80w90 and a gallon of Lucas oil stabilizer (split between both finals). Truth be told I want to run the Cat TDTO 50 (in trans and finals)…but knowing the fluids in this machine are 10-12 years old(!) and have been “topped off with 15W40 engine oil” by PO, I figure why “waste” the Cat oil. My machine has some leaks and with the “sludge” that is likely in the various compartments; my plan is to hit the fluid reset “button”, run everything for a while, then change oils/filters (long before the decade mark!!). I also prefer changing oils when they’re HOT…everything is “mixed-in” and flows better.
BTW, I now appreciate how difficult it is to clean/flush a final drive compartment- it’s dam tight in there! Since I’m juggling a few maintenance/repair items, I was NOT able to have the tracks up off the ground…this eliminated me from rotating the tracks while flushing the final with (small amount) of Kerosene…I’m VERY confident I would have gotten much more crap out... next time!
Are you going to “hurt” your old final using 140 weight, doubt it. Probably the same can be said for a 30 weight! Then factor location “average” temp and your choices quickly narrow into the 40-90 “range” (likely).
Lastly, I do believe certain oils have negative effects on the seals…but most seal leaks are caused by out of adjustment wear, age, or casualty of some other breakage.
Hey- just the fact you’re getting old oil out and new oil in is huge! …and you got a data point on the magnet too!!
I won’t even bitch about the lack of supply for oils/grease up this way…
Wow…checkout the “choices” in the grease gun isle!!

Mcrafty1 · Aug 18, 2022

D5Dan said:
View attachment 266251 View attachment 266252

Hey Mcrafty, as I’m sure you’ve done, I looked thru several HEF projects/recommendation posts, then on my 67/68 D5 I used Tractor Supply 80w90 and a gallon of Lucas oil stabilizer (split between both finals). Truth be told I want to run the Cat TDTO 50 (in trans and finals)…but knowing the fluids in this machine are 10-12 years old(!) and have been “topped off with 15W40 engine oil” by PO, I figure why “waste” the Cat oil. My machine has some leaks and with the “sludge” that is likely in the various compartments; my plan is to hit the fluid reset “button”, run everything for a while, then change oils/filters (long before the decade mark!!). I also prefer changing oils when they’re HOT…everything is “mixed-in” and flows better.
BTW, I now appreciate how difficult it is to clean/flush a final drive compartment- it’s dam tight in there! Since I’m juggling a few maintenance/repair items, I was NOT able to have the tracks up off the ground…this eliminated me from rotating the tracks while flushing the final with (small amount) of Kerosene…I’m VERY confident I would have gotten much more crap out... next time!
Are you going to “hurt” your old final using 140 weight, doubt it. Probably the same can be said for a 30 weight! Then factor location “average” temp and your choices quickly narrow into the 40-90 “range” (likely).
Lastly, I do believe certain oils have negative effects on the seals…but most seal leaks are caused by out of adjustment wear, age, or casualty of some other breakage.
Hey- just the fact you’re getting old oil out and new oil in is huge! …and you got a data point on the magnet too!!
I won’t even bitch about the lack of supply for oils/grease up this way…
Wow…checkout the “choices” in the grease gun isle!!

This came to me from another forum, it's the reason I was thinking the heavy gear oil would be good for the old machine and the fact that I just use it in the summer months.

"As I remember back in the day there were only two grades of oil used in the D6, HD30 series 3 engine oil every where except the hydraulics which took HD10, due to the ever recurring final drive failure that plagued all Cats of that era most people took it upon themselves to use gear oil in the final drives in the hope it would reduce the slap in the poorly engineered gears that the hardness was very shallow and wore off after a few years service causing the teeth to pick up and fail, the capacity of the components is usually quoted from when they are dry, I have scribbled in my notebook Engine 26Lts, Trans 64Lts and finals 15Lts, good luck with your machine, great machine no computers or other crap on them, you will be well happy with it."

Bluox · Aug 18, 2022

Mcrafty1 said:
This came to me from another forum, it's the reason I was thinking the heavy gear oil would be good for the old machine and the fact that I just use it in the summer months.

"As I remember back in the day there were only two grades of oil used in the D6, HD30 series 3 engine oil every where except the hydraulics which took HD10, due to the ever recurring final drive failure that plagued all Cats of that era most people took it upon themselves to use gear oil in the final drives in the hope it would reduce the slap in the poorly engineered gears that the hardness was very shallow and wore off after a few years service causing the teeth to pick up and fail, the capacity of the components is usually quoted from when they are dry, I have scribbled in my notebook Engine 26Lts, Trans 64Lts and finals 15Lts, good luck with your machine, great machine no computers or other crap on them, you will be well happy with it."

That story should have started 'Once upon a time'.
Cat has always recommended Sae50 lube oil not motor oil in their machines in that time period.
The specs call if the machine started above 32 degrees.
Oil change at 1000 hours or 6 months.
So I guess the question is how many hours are you gona run a year?
Bad Bob

Mcrafty1 · Aug 19, 2022

So are you saying 50w in transmission also or just the finals?

Bluox · Aug 19, 2022

A TO-4 spec 30 SAE in transmission.
Bad Bob

.RC. · Aug 19, 2022

I dunno about elsewhere in the world, but here Cat TDTO 50 oil from the dealer is far cheaper then any other oils from the fuel/oil distributors. Although Cat do make a dedicated final drive oil which is more expensive FDAO 50/60. eg: https://www.monarchparts.com/caterpillar_fdao_oil

I suppose when you think about it TDTO oils for basic gearboxes like a final drive may not be the best choice, as modern transmission oils can not be super slippery otherwise gearbox clutch packs would never work.

We just run cat oils of whatever type required in everything that does not require specialised oil.

Mcrafty1 · Aug 19, 2022

Bluox said:
A TO-4 spec 30 SAE in transmission.
Bad Bob

Thanks, That is what I have in the Transmission now. I also found in my manuals that CAT listed 140w for the finals above 32*F

Mcrafty1 · Aug 19, 2022

.RC. said:
I dunno about elsewhere in the world, but here Cat TDTO 50 oil from the dealer is far cheaper then any other oils from the fuel/oil distributors. Although Cat do make a dedicated final drive oil which is more expensive FDAO 50/60. eg: https://www.monarchparts.com/caterpillar_fdao_oil

We just run cat oils of whatever type required in everything that does not require specialised oil.

I have NOT priced any oils from CAT so I can't say that isn't true here but I buy SINOPEC brand oils shipped free to my door at prices well below the outlets that carry most oils I use locally.

Mcrafty1 · Aug 19, 2022

Bluox said:
That story should have started 'Once upon a time'.
Cat has always recommended Sae50 lube oil not motor oil in their machines in that time period.
The specs call if the machine started above 32 degrees.
Oil change at 1000 hours or 6 months.
So I guess the question is how many hours are you gona run a year?
Bad Bob

That story came from The Yesterdays Tractors forum, a poster AJ replied to me a while back with that answer to a fluid capacities question. I suspect he is in Australia but I'm not sure about that. I know when I ask questions on forums I'm going to get a wide range of answers, I'm looking for info when I ask so I don't make it a habit to call ANYONE wrong with the replies I get. There's usually a wide range of answers when ever questions are presented on any forum. Cat also lists 140w oil for the finals above 32*F for anyone that's interested.

At 66 years old my machine will most likely not see 1000 hrs. of service in the rest of my working career, and the hours it does get will be summers.

Bluox · Aug 19, 2022

I have only been doing this for 50 years and that is what Cat recommends for your tractor.
If you look up Cat oils FADO 60 is for large trucks and scrapers finals a different set of gear types.
Cat sells 85-140 GL for scraper and wheel tractors.
But you can use whatever you want.
You should be old enough to know about half of what you read on the internet is bull crap.
Bad Bob

Mcrafty1 · Aug 19, 2022

I got the 140 spec for my machine from the book Cat sold me that covers my serial # I hope it ain't all bull crap, the manuals cost me $280.00. if the spec has changed I would hope they would have updated the manuals. I'm not looking for a pizzing contest, I'm just saying what the book tells me. And no, I don't believe everything the internet says I'm more inclined to go with the product manuals.

John C. · Aug 19, 2022

Can you post a photo of the page that says 140wt? I've never heard of or seen that specification either.

D5Dan · Aug 19, 2022

Also wondering if the updated/supplemental pages are stuffed at the end of your manual??

Like you said, I’d like to think you would have gotten the most up to date info…

Mcrafty1 · Aug 19, 2022

I am at the lake until Sunday but will be glad to post it when I get back home.

John C. said:
Can you post a photo of the page that says 140wt? I've never heard of or seen that specification either.

Mcrafty1 · Aug 19, 2022

D5Dan said:
Also wondering if the updated/supplemental pages are stuffed at the end of your manual??

Like you said, I’d like to think you would have gotten the most up to date info…

The Specs are listed on page 7 of the maintenance and lubrication chart with all the other lube specs.

Bluox · Aug 19, 2022

Look on the back page of your book for the publish date bet it's late 70s.
Bad Bob

Cat D6C Final Drive Oil

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