Posts: 1061
Joined: 7/18/2006 From: Champaign, IL Status: offline
Anyone ever wonder why transmission fluid and rear end fluid will hold up for like 60,000 miles but engine oil is changed every 3-5000? I mean both have lots of moving parts, both operate under high loads and high temperatures. anyways i was just wondering if anyone else had ever considered this?
of course i change my oil religously but i was sitting around on my ass and that thought popped into my head
Posts: 1061
Joined: 7/18/2006 From: Champaign, IL Status: offline
quote:
ORIGINAL: v6stang07
transmission fluid is also a lot thicker than motor oil but yea that is true, they both serve a purpose and are really equally important???
that makes sense transmission and rear end fluid are a lot heavier weight which is probably why they last a lot longer, anyways i was bored and thinking
Anyone ever wonder why transmission fluid and rear end fluid will hold up for like 60,000 miles but engine oil is changed every 3-5000? I mean both have lots of moving parts, both operate under high loads and high temperatures. anyways i was just wondering if anyone else had ever considered this?
of course i change my oil religously but i was sitting around on my ass and that thought popped into my head
You're leaving out one KEY difference. Differentials and transmissions are sealed systems. Engines have a constant flow of Air and Fuel being run through them. The temperature combined with the fuel and oil create carbon aka sludge. It's the carbon build-up (which is like microscopic sandpaper) that you are changing the oil out in the engine every 3K miles.
Tranny's and Diffs usually only contaminate when they A) Leak, or B) have excessive internal wear.
would be cool to see the outcome, get a junker car and change the oil with diff fluid. just to see what happens.
It would sieze. Too thick of oil and it can't get into the smaller passageways so you would end up with metal-to-metal contact even though there is flow. Plus the pressure would be way low so even if the molecule could fit between the metals it would not have sufficient pressure to move it. Thicker oil = bigger molecules.
Posts: 1061
Joined: 7/18/2006 From: Champaign, IL Status: offline
quote:
ORIGINAL: Derf00
quote:
ORIGINAL: laserred02
Anyone ever wonder why transmission fluid and rear end fluid will hold up for like 60,000 miles but engine oil is changed every 3-5000? I mean both have lots of moving parts, both operate under high loads and high temperatures. anyways i was just wondering if anyone else had ever considered this?
of course i change my oil religously but i was sitting around on my ass and that thought popped into my head
You're leaving out one KEY difference. Differentials and transmissions are sealed systems. Engines have a constant flow of Air and Fuel being run through them. The temperature combined with the fuel and oil create carbon aka sludge. It's the carbon build-up (which is like microscopic sandpaper) that you are changing the oil out in the engine every 3K miles.
Tranny's and Diffs usually only contaminate when they A) Leak, or B) have excessive internal wear.
good call i didn't think of that. well that answers my curiousity then.
Anyone ever wonder why transmission fluid and rear end fluid will hold up for like 60,000 miles but engine oil is changed every 3-5000? I mean both have lots of moving parts, both operate under high loads and high temperatures. anyways i was just wondering if anyone else had ever considered this?
of course i change my oil religously but i was sitting around on my ass and that thought popped into my head
You're leaving out one KEY difference. Differentials and transmissions are sealed systems. Engines have a constant flow of Air and Fuel being run through them. The temperature combined with the fuel and oil create carbon aka sludge. It's the carbon build-up (which is like microscopic sandpaper) that you are changing the oil out in the engine every 3K miles.
Tranny's and Diffs usually only contaminate when they A) Leak, or B) have excessive internal wear.
good call i didn't think of that. well that answers my curiousity then.
Anytime.
< Message edited by Derf00 -- 6/1/2007 4:39:40 PM >
transmission fluid is also a lot thicker than motor oil but yea that is true, they both serve a purpose and are really equally important???
Hate to inform you but you are wrong. Trans fluid is NOT thicker than oil. ATF is really thin in comparison.
And as for the original question why you need to change it so often is because during the combustion process, when the air/fuel mixture ignites, not all of the gases are expelled out the exhaust. Some of the exhaust gases actually blow by the piston rings. These gases then mix with the oil creating a highly acidic condition. At a certain point, about 3k miles, the acid level is so high that itll actually start to deteriorate gaskets and seals. Thats why its recommended that you change your oil every 3k. Not because the oil looses its lubricating properties.
And ideally, if you want your trans to last you should change the fluid every 15k, regardless if its an auto or a stick. And if you drive your car hard a lot of the time you should change it more frequently than that. -P.
transmission fluid is also a lot thicker than motor oil but yea that is true, they both serve a purpose and are really equally important???
Hate to inform you but you are wrong. Trans fluid is NOT thicker than oil. ATF is really thin in comparison.
And as for the original question why you need to change it so often is because during the combustion process, when the air/fuel mixture ignites, not all of the gases are expelled out the exhaust. Some of the exhaust gases actually blow by the piston rings. These gases then mix with the oil creating a highly acidic condition. At a certain point, about 3k miles, the acid level is so high that itll actually start to deteriorate gaskets and seals. Thats why its recommended that you change your oil every 3k. Not because the oil looses its lubricating properties.
And ideally, if you want your trans to last you should change the fluid every 15k, regardless if its an auto or a stick. And if you drive your car hard a lot of the time you should change it more frequently than that. -P.
I was thinking Gear Oil (differential). Tranny fluid (ATF as used in our cars) is indeed thinner than motor oil. But, the rest of my point still stands, Closed vs open system.
For the record some import manual tranny's actually use Gear oil not ATF
< Message edited by Derf00 -- 6/1/2007 4:42:40 PM >
Posts: 2914
Joined: 12/15/2006 From: Lafayette/Gulf of Mexico, LA Status: offline
Tranny fluid actually is used in engines at times, as it has a for good detergent quality. I used it on our old work truck when it got sludged up. It's a lot thinner so it gets everywhere and then breaks the sludge down. Of course you can't run it in there very long. I put in 1 quart for an oil change, and emptied it after 30 minutes of running and it was nasty as hell. I did that 5 times, only because the sludge was really really bad, and it just kept pluggin filters and came out the drain almost slow! But it really helps clean the engine, of course with it being so thin, it slips past the rings very easily and trace amount of buring tranny fluid would come out of the exhaust, but only around the time that I would be ready to drain and refill it anyway. I need to do one more drain and refill on it, run it about 200 miles and change it all out again, just to make sure that pretty all the tranny fluid is out of there.
I've considered doing it to my car, since I do have 80k on it now, just half a quart for 300 miles and then do an oil change run it again with half a quart 300 miles and change it out again and it should be good and pretty inside.
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engine oil vs. tranny fluid - 
Anytime. 
