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New to me D8K, operation, maintenance, adjustments
- Thread starter Alberta Farmer
- Start date
John C.
Senior Member
Here is a discussion on this forum for a few years back on the subject.
https://www.heavyequipmentforums.com/threads/d6c-final-drive-question.12089/
We never used gear oil in Cat finals.
https://www.heavyequipmentforums.com/threads/d6c-final-drive-question.12089/
We never used gear oil in Cat finals.
my d8h tips the scales at about 79000lbs with 8a blade, front mount hyd, light canopy, 6 roller track frames and only a drawbar- therefore 8k with ripper is a lot heavier. I've had mine hauled a couple times and had to go across weigh scales. my parts book says dry weight basic machine is 47290lbs- no hyd, no hard nose etc
Manu
Active Member
Ok...that chart is likely for a stripped down D8 for agricultural application where it pulls cultivators and seeders so it doesn't cause excessive ground compaction
Manu
Active Member
In western Canada D8Ks built roads in mountains and hills. They pushed out rock, boulders and big stumps in logging and mines as well. To do that they had to be guarded and beefed up to do the job. If the D8K in Alberta came from some stockyard where it was used for just pushing animal waste or landfill it wouldn't need heavy guarding or reinforcement of blade and pusharms.
Check Break
Senior Member
We have three K-s and a late model H. All 8S and 4BBL (2 shanks). All heavy guarded with pushblocks. The H with ROPS weighs 83.5K and the K-s (1) ROPS and (2) EROPS between 85 and 87K. 30w in the transmission. 50w in the finals.
Manu
Active Member
Ok..maybe my information about weight is not accurate.I don't drive a low bed truck so cannot confirm from personal experience going across scales and doing the math. I vaguely recall a number of 120,000 lbs but maybe that was a gross weight which included the truck and trailer. The other thing is maybe the truckers exaggerated. I'll have to ask my older brother..he was a dealer mechanic for 38 years and two of his sons are excavator operators that also drive their low beds..their dozers are little D6Ns..
Nige
Senior Member
And those are both engine crankcase service classification viscosity grades, not gear oil. An 50 on the SAE crankcase scale is in the same range viscosity-wise as a 90 on the SAE gear oil scale.
Check Break
Senior Member
I vaguely recall a number of 120,000 lbs but maybe that was a gross weight which included the truck and trailer.
That's where your number is coming from. The K-s weigh out a little over 126K on a Murray 5 axle, more on another brand trailer with another bump if your tractor is not optimally set up for heavy haul. Nige pointed out a little detail I'd forgotten, the oil being based on an engine service rating. Pretty important if you're out of oil and just looking for something to top off a system. We went with Mobil a long time ago and now I realize my brain focused on which product goes in which fill plug without remembering why. I only remember one occasion where we lost so much hydraulic fluid on a weekend that we bought everything Walmart had to get by. When that job ended, the hydraulic system was drained and whatever hoses replaced. The rest of the time I had the Mobil distributors mapped out. They treated us well and I remember some of them would open up after hours if we got in a bind.
That's where your number is coming from. The K-s weigh out a little over 126K on a Murray 5 axle, more on another brand trailer with another bump if your tractor is not optimally set up for heavy haul. Nige pointed out a little detail I'd forgotten, the oil being based on an engine service rating. Pretty important if you're out of oil and just looking for something to top off a system. We went with Mobil a long time ago and now I realize my brain focused on which product goes in which fill plug without remembering why. I only remember one occasion where we lost so much hydraulic fluid on a weekend that we bought everything Walmart had to get by. When that job ended, the hydraulic system was drained and whatever hoses replaced. The rest of the time I had the Mobil distributors mapped out. They treated us well and I remember some of them would open up after hours if we got in a bind.
Nige
Senior Member
Another thing to remember is the the additives in EP gear oils have been known to degrade the silicone rubber in Duo-Cone Toric Rings and cause premature leaks and/or seal failures
Cat strongly advise against the use of EP oils in any compartment that has a Duo-Cone seal in it. The attached Service Mag for excavators is just one example.
Cat strongly advise against the use of EP oils in any compartment that has a Duo-Cone seal in it. The attached Service Mag for excavators is just one example.
That's not entirely true, cat tractor scrapers still use 90 wt. in diffs and final drives with duo cone seals.
Bob
Manu
Active Member
Interesting information..I didn't recall that service letter..but don't recall the sprocket seals being silicone...although methinks the input pinion from the steering clutches is. That explains why they fail and overfill the final drives with transmission oil..which could cause a failure of the sprocket seal. Although typically sprocket seal failure occurred from dirt forcing itself into the ramp of the toric ring and eroding it and the duocone rings..plus wire etc. that gets wrapped around it when a machine is used in a garbage dump. It is a good illustration of the benefits of a high drive.
Manu
Active Member
That service letter refers to excavators with planetary drives..as do haul trucks which have silicone toric rings. Gear oils have a phosphorus additive which is a smelly lubricant enhancer which spur gears need because of extreme pressure as single gear teeth slide into each other. Planetary gears can get by without it because the force is spread over more teeth.
50 wt lube oil has been the recommended oil for D8H&Ks finals since at least the late 60,s so if you are using 90 wt you are causing the final drive seal failures.
Bob
Nige
Senior Member
I’ll be honest and say that for big iron (yellow or otherwise) I personally detest EP oils with a passion. Cat generally stay away from EP so it’s not normally an issue, but I’ve seen plenty of cases on machinery from other OEMs where EP oils have been replaced very successfully with either SAE50 TO-4 or SAE60 FD-1 oil depending on the machine and the ambient temperature range. Currently we run the swing drives, pump drives, rotary heads, and finals of a fleet of Hitachi 3600’s and Atlas Copco DML drills on 60-weight FD-1. The OEM Manual recommended EP90 oil in every case. The improvement in the oil condition as shown by analysis is like night & day.
John C.
Senior Member
I've run EP oils in Hypoid and Amboid differentials forever. Cat runs bevel gears in their differentials on wheel loaders and as such never needed the smelly snot for lube. I've have used a lot of EP oils in line cranes. It always seemed to me that kind of oil was for applications that applied very high torque requirements across point loaded surfaces or in places that had extensive sliding surfaces under extreme stress like swing and traction drives in cranes.
Manu
Active Member
Yes..that is why if it was my dozer I would use that oil in the final drives after maybe sourcing toric rings that were compatible with it. The main cause of seal failures in those machines is not the oil it's the dirt packing into the seal area. That's why when the sprockets are off...the seal protectors are replaced. In one area where the dump had lots of pulpmill bale wire we welded 1" blocks on the case and sprocket so it would cut the wire before it wrapped into the seal. It sort of worked.
Manu
Active Member
Yes EP oil has a disgusting smell..particularly when a machine has caught fire and burned that oil.It would make a maggot gag.
correct me if i'm wrong but EP gear oil was designed for hypoid gearsets where the pinion is mounted below(or above) the centerline of the crown gear which results in a wiping action of the pinion teeth across the crown gear teeth. regular spiral bevel gearsets where the centerlines are in the same plane do not necessarily need EP oil although it may be used. cat kept it nice and simple-you could use engine oil anywhere and keep it running(especially out in the bush)
Manu
Active Member
Methinks you are correct that in differentials it is very important but having seen a D8 final drive apart due to failure my feeling is it is critical to have the best lubricant possible. However if for some reason you have no lubricant like if someone forgets to tighten the drain plug and it falls out and all the oil is lost...Then engine oil is better than nothing if that was all you had and had to move the machine several miles. In all fairness engines have gears that rely on the lubricity and additives that might help a final drive from suffering damage if it was just being moved.