when is engine oil ok in a gearcase?

[1 FMF]

What are the lubrication requirements for the various types of gear designs?
I know for a spiral beveled type gearset (is that hypoid?) that there's sliding action as the gears mesh and that requires a lube with extreme pressure additives, a GL-5 gear oil for example.

What are the other types of gears out there?

Reason I ask is I was reading on iboats about volvo 270 outdrives which call for a 10w-40 engine oil as a lube. I know nothing about them, but I imagine that has to be due to the types of gears that are in the drive. In the case of Mercruiser Alpha outdrives, I've seen the gears in them and can understand why you need a "gear oil".

Anyone have or know where to get info/specs on lubriplate type C gear oil- it's the oil for electric shift outdrive/lower units.

 

[Ken2]

Engine oil is OK in a gearcase when the gear makers says it's OK. The gearcase often connected to Detroit 8V-71 marine engines takes SAE 40 engine oil. Don't guess. Follow the manufacturer's requirements. Not only is the gear tooth contact a consideration, like the sliding action of hypoid gears, but also the bearings inside the gearbox need to be considered.

Hypoid is when the shafts of the bevel gears are not on the same plane. Notice how the driveshaft into a differential is usually lower than the axles? That's hypoid.


Ken

 

[Doug Hillary]

Hi,
1 FMF - I agree with Ken2's comments

The Vovlo unit may be a suitable application for a specific synthetic oil such as;

Castrol 50E or,
Mobiltrans SHC 30 or 50

These work extremely well in gearboxes where an engine oil is specified. Usually they significantly lower operating temperatures

Doug

 

[1 FMF]

thanks.

quote:

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Originally posted by Ken2:
Engine oil is OK in a gearcase when the gear makers says it's OK.

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but I want to know **why** they say it's ok.

 

[Ken2]

Because the gear tooth contact pressure and sliding action require certain attributes in the lube. I've spend most of my working time with high horsepower double reduction double helical gears running in very light, very low additized turbine oil, but everything was made to run that way, including the babbit bearings. The high speed gear turned about 6000 rpm, and the low speed gear turned about 100 rpm. Separate gear boxes used highly compounded gear oil, because that's the level of protection those gears needed. Engine oil is OK for gears like timing gears inside an engine and the accessory drive gears in the crankcase of some diesels, and the gears are engineered to run in the oil available.

You could make auto differential gears that run in engine oil, but they'd have to be much bigger with lower gear tooth contact pressure and no hypoid sliding action. The small gears in some modern differentials require synthetic gear oil for the higher film strength and resistance to oxidation in the heat, especially the microheating at points inside the gear tooth contact patch.


Ken

 

[montero91]

my bently manual for my '84 bmw 533i says " using engine oil or atf in the manual transmission will not affect the service life of the transmission, although BMW reccomends that the heavier gear oil be used during warmer months". it also says that a non-hypoid type SAE-80 gl-4 be used but then refers to alternate oils in the text(the bently manual).these are sae 20 and 30 and 40. for dif. temp. situations, -10 to +120 fahr.

 

[Gurkha]

On my MB ZF transmission, I have been always tempted to use M-I Super Synthetic 5W-50 but have been afraid to do so since the manual only calls for ATF, I can't get synthetic ATF here so was wondering if the M-I would provide better protection in the summer months as well as for heavy off road duty in slippery wheel spin inducing conditions. Anyone else tried synthetic oil in transmission please respond.

 

[ecclestone]

Gurkha
Going from and ATF to a 5w 50 is a
large jump in viscosity. A typical ATF is around an SAE 10. Manufacturers recommend ATF fluids to ensure smooth shifting in transmissions that may have straight cut or not true helical gears. I would recommend a OW - 30 in synthetic oor mineral. You "may" experience a slight crunch in engaging gears from cold as the heavier oil may not slow the baulk ring synchro hubs as quickly as previously. My experience has been that such a move also stops "hot rattle" where the main shaft bearing and clutch release bearing noises are transferred up the gear stick during normal driving. Either way it certainly wont do any damage whatsoever.

 

[Gurkha]

Great,I was actually thinking of using it for the 40C+ summers, for winters I would stick to ATF. I am just worried about shear with ATF in extremely hot conditions.

 

[Tourist]

Hi. Aren't engine oil and ATF very different althogether? One is oil and the other merely some sort of fluid (F)?

btw, a lot Isuzu uses engine oil. Using gear oil makes it very difficult to shift.

 

[Jimbo]

Almost all Japanese motorcycle transmissions share the same oil supply with the engine, 10W-40. Early Honda automobiles specified 10w30 engine oil. However, many of those Honda cars had early transmission failures. Shearing of multi-vis oils decades ago may have been a factor.

Older BMW and Mercedes manual transmissions often recommended straight weight engine oil.

Hypoid and worm gear sets are the ones that have sliding contact and generally high tooth pressures, reqiring EP additives. Helical gears are most common in automotive (manual and automatic) and motorcycle transmissions, so the lubricant formula is not as critical for the gears.

 

[Tourist]

Hi. So if Isuzu recommends engine oil in their transmission, would it be better to use a straight weight oil...say...40W instead of 15W40?