Reason Can not Use Engine Oil in Trans

[herbid]

Just my second opinion,
a copy from this site:
http://www.carbibles.com/engineoil_bible.html

"Overfilling will mean the crank dips into the oil and churns it into a froth. Froth is good on certain types of coffee but not good in an engine. The mixture of aerated oil will be forced into the bearings and in case you didn't know, air is not a lubricant. Typically this means that bearing damage will follow quite rapidly, especially if you are driving on a motorway. You'll know bearing damage when you get it. The engine smells like a garage mechanic cooking over an open flame and the noise coming from the engine is the sort of thing you'd normally hear in vaudeville plays when a piano is pushed down a flight of stairs. As if that all wasn't bad enough, the excess oil gets thrown up into the piston bores where the piston rings have a hard time coping with the excess oil and pressure. It gets into the combustion chamber and some of it will get out into the exhaust system unburned resulting in a nice patina of oil all over the platinum surfaces of your catalytic converter. This renders it utterly useless for good."


So the same condition happen in Trans gear where the bottom gear dips into the oil.

That might be the biggest consideration not using engine oil in Trans.

Correct me if I am wrong.

 

[ryan2022]

hmm,

I'm not sure what you're saying. If you're talking about ATF, the frictional properties and viscosities are totally different.

If you're talking about Manual transmission fluid, there are a lot of cases motor oil was called for in the past in light duty manual transmissions. Honda used it for years, but in the past decade, there have been MTF's with better friction modifyers and additives developed.

A gearbox is a bit different too. The gears are usually sitting in the oil. There is usually no pump in a manual transmission, and the gears churn through the oil. Its very difficult to overfill most manual transmissions as well.

 

[herbid]

Sorry forget,
I mean manual trans.

 

[ryan2022]

Well, Motor oil has been used in the past. Up to the mid-nintees, Honda used it extensively.

The Honda manual transmission fluid, GM synchromesh and Penzoil's universal MTF, are all very close to the viscosity of 5w30. they just have better additives, suitable for transmission use now.

This being said, I had over 290K on an integra my Dad used to drive, using nothing but motor oil.

 

[ryan2022]

Well, Motor oil has been used in the past. Up to the mid-nintees, Honda used it extensively.

The Honda manual transmission fluid, GM synchromesh and Penzoil's universal MTF, are all very close to the viscosity of 5w30. they just have better additives, suitable for transmission use now.

This being said, I had over 290K on an integra my Dad used to drive, using nothing but motor oil.

The gears dip in the oil. Thats why its important to keep it at the recommended level. If its too low, usually 5th gear suffers as its the shortest physical gear, and tends to run dry.

Like I mentioned before, you cant really drastically over fill a transmission.

 

[flacoman]

Mini Coopers had the engine and trans on the same sump!

 

[Eddie]

The transmission oil required depends to the types of gears used. GL5 is used for Hypoid or worm gears due to more sliding friction. Spiral bevel and ? have less sliding friction. Helical and spur gears are almost all rolling friction and therefore you can use ATF or engine oil. Therefore the additive packages are intirly different.

 

[MGregoir]

Originally Posted By: flacoman
Mini Coopers had the engine and trans on the same sump!


Hence the development of 20W-50.

Cue Doug Hillary.

 

[Captain_Klink]

My transmission calls for gear oil, but i mix 50:50 gear oil and Mobil 5w30 EP to thin it out a bit, and it runs extremely nicely.
the tranny calls for GL4, and since GL5 has about twice the additives of a GL4, then thinning it out with 50% motor oil probably is good. And if you're wondering that I'm not stressing the gears, I do tear around in it, and push the rpm's. It is a 1995 Mitsubishi Mirage, with a 1.5 NA 12 valve engine and a 5 speed stick shift.

 

[PT1]

Originally Posted By: flacoman
Mini Coopers had the engine and trans on the same sump!


Man motorcycles use shared sump for engine/trans/clutch. You just need a stout motor oil designed for it.

 

[Steve S]

http://upload.wikimedia.org/wikipedia/commons/c/c6/Engine_and_Gearbox_cutaway-001.jpg click to enlarge.

 

[mechtech2]

The good news is that you don't have a catalytic converter on your manual trans. One less thing to worry about.

There are a few manual trannys/transaxles that spec engine oil as OK. Synchromesh gear lubes are a similar viscosity, but are much better designed.
Engine oil is never my first choice, for a bunch of other reasons.