So we know gear oil can't be used in the crankcase

[Lumberg]

...for reasons discussed in gruesome detail in this forum.

However,

I am curious if the converse is also true?

For example, say you took a PCMO or even HDEO and maybe put an additive in there, or just be crazy and add a dollop of EP grease to the mix.

What would happen if you put something like that in a differential?

 

[Solo2driver]

Certain manufacturers used to recommend engine oil in their transaxles (like Honda in the '80s and '90s), and now specify a Manual Transmission Lubricant/MTL.

I don't think that any engine oil has enough EP additives in there to function properly in a differential/ring gear environment...take a look at the UOA/VOA section of gear and transmission oils.

With gear oil prices what they are (same as motor oil) and the length of service (50K-150K miles), why even bother?

 

[MolaKule]

Bad idea there as well. As Solo stated, no EP additives to protect the gearing and bearings.

In addition, gear oils are made of mixes of heavy base oils, whereas PCMO and HDD's are made of light to medium weight base oils, so engines oil would not have the film strength to protect gearing teeth and bearings, which experience very high loads.

 

[Chris142]

My old Peterbilt uses SAE50 engine oil in it's transmissions as does my 1973 I.H. pickup.

I think engine oil should work fine in a transmission.

You definatly do not want to put engine oil in a rear end. Rear end ring and pinons slide when they rotate vs straight cut gears in a trans.

 

[MolaKule]

I assumed Lumberg was discussing differential lubricants.

 

[artificialist]

yes, he must be talking about hypoid differential lubricants.

In transverse engine applications where the differential is separate (Certain Toyota models) ATF is called for.

However, in cases where the FWD vehicle doe not use a transverse mount (older Subaru, older SAAB, Dodge Intrepid/Chrysler LHS/300M, 5th generation VW Passat) the differential is always made separate, and ALWAYS requires hypoid gear oil.

And gear oil is sometimes used in the crankcase. when an engine has worn out bearings, putting gear oil in there helps quiet it down enough for you to trade it in and get a better resale value.

 

[Lumberg]

I think I may be confused as to nomenclature.

In my world, a rear end and a differential are almost synonymous. More accurately, differentials are a superset of rear ends.

What's the diff?

 

[Big Jim]

Originally Posted By: Lumberg
I think I may be confused as to nomenclature.

In my world, a rear end and a differential are almost synonymous. More accurately, differentials are a superset of rear ends.

What's the diff?


And what do you call it on a front wheel drive car? The front end?

 

[tdi-rick]

Engine oil used to be specified in older tractor transmissions and final drives, and these use spiral bevel, but not hypoid crown wheels and pinions.
Castrol here supplies Agri engine oils with a GL4+ equivalent add pack level. http://www.tds.castrol.com.au/pdf\5823_AgriMPPLUS_111726_200610.pdf

 

[MolaKule]

In a conventional four-wheel drive vehicle, you have a front differential and a rear differential.

In a front-wheel drive vehicle, the differential is inside the transverse mounted transaxle.

A differential can be of many types, but the modern hypoid configuration is the most prevelant in differentials in which the diffy is by itself in it's own case. This may not be the case for a transaxle.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=729255#Post729255

 

[artificialist]

Originally Posted By: MolaKule

In a front-wheel drive vehicle, the differential is inside the transverse mounted transaxle.

USUALLY that is the case.
earlier in this thread, I listed some of the odd cases where the car is FWD, but not transverse.