1. Why does ATF fluid level change so much between cold and hot (both running) but engine oil stays the same? 2. For reasons I'd rather not discuss, I had to drive my truck in four wheel low into town, with the engine taching up pretty good. About halfway there smoke started pouring out from underneath. I slowed down and it stopped. Now down a quart of ATF. So wet can't tell from where. What happened?
one reason it expands so much is because it gets so hot, the torque converter turns engine power into heat.
The level changes due to expansion from heat. Basic physics you forgot from grade school. As atoms heat up they excite and move faster resulting in expansion.
Sounds as logical as anything, thanks. But, I had just left my driveway cold and gone about 1 mile when fluid started burning on the pipes. I don't think the trans would've gotten that hot that quick but it could have thrown the fluid up there by spinning so fast. Going to crawl under for a better look..
Its gets hotter and it is a different type of oil than engine oil. It has to take more heat then your engine oil and it is processed in such a way as to handle more heat without breaking down. @Blues4U can give you a better answer than that but that is the gist of it.
I would guess that your pump spinning so fast made too much volume for some part of the transmission to handle. That is why it pushed out somewhere. Now why it wouldn't push out on a 10,000 rpm race engine I have no idea.
It's a 700R4. Got under it today, top is dry by the vent. Might have come out the dip stick tube at the bottom, that's a little loose. Read a couple interesting theories on the fluid rise when warm. One, since the valve body takes up a bunch of space in the pan, the reduced area will cause the expanded ATF to rise higher than it would in say an engine oil pan. The other was that cold ATF would tend to cling to the internal parts of the transmission more than when hot where it tends to drain into the pan faster. True? Sound interesting anyway..
did you have a snow plow on the front? high rpm's, slow speed reducing air flow and a snow plow forcing air away from radiator =over heated ****** fluid.
Roger- No means to be a smart *** here....... When have you EVER seen a plugged filter? If one is plugged, I don't think the trans would move at all!
Back in the day......th400/425's were always kept a quart low, Just for this reason..... All were checked when hot. But- That was then..... I still check em' when good and warm.
No plow but my spare tire is in front of the grill. Has never been a problem, engine runs cool. Hmm..
This could be alot easier if you give all the information up front.Years ago when some gm trans were rebuilt they would blow the aftermarket front pump seal out. The fix was to remove the check ball.The only problem with that is it lets the converter drain back into the pan which makes it overfull until you start it.So it leaks out anywhere it is not sealed properly usually the dipstick tube.
The only one I have ever plugged was on this very trans. About a year ago my radiator sprung a leak. I had it rebuilt at ye old radiator shop in town. The very next time I drove it, about 20 miles later, it started shifting later and firmer, then all of a sudden, like the flip of a switch, wouldn't move at all. Managed to get it into a parking lot. Pulled the pan, changed the filter, good as new. I suspect **** from the hot tank at the radiator shop got into the built in trans cooler. Been fine ever since, with lots of heavy towing thrown in. Moral of the story: If you have your radiator tanked make sure and flush out the trans cooler if so equipped.
Yes on Gene Adams blue square body truck , it wasn’t totally plugged, fluid running out of the top of dip stick tube. Gene mentioned it to me ,I called Bob Williams a friend of mine that owned clutch & gear in Bellflower, and then Bobs driveline in Victorville
Well the atoms don't expand. They do move faster and therefore further apart from each other causing the expansion of the fluid. Can't stop being a teacher even though I'm retired...
The odd thing is that oil (and pretty well all liquids) only expand a very small amount with heat. I got values from the "Engineers' Toolbox" site for engine oil, which should be about the same as for ATF; heating it from 60 F. to 260 F. only increases the volume 8%. But I suppose the fluid in the torque convertor and p***ages will expel their increased volume, so the level in the pan will raise more than 8%. If half the ATF is contained that way, then all the expansion will have to occur in the pan, raising it's level 16%. And as has been mentioned, the valve body takes up space in the fluid, so the level around it will rise more than the 16%. The high hot level is starting to make sense now.
I saw one transmission, 727 in this case, where the converter had to be cut off the crank with a cutting torch. The converter was welded to the crank. The ****** was in a 4x4, and he blew it up real good. Is that hot enough for you? My friend, who owned a transmission shop, and he said the biggest enemy of transmissions is heat, and people don't realize how much heat is building up in a transmission when the rpm isn't high enough to lock (relative term) the converter. I run synthetic ATF in all my automatic transmissions, to help lengthen the service life. The transmission runs cooler, works better in the cold, and shifts more quickly. I have been running it in the TH400 behind my big block in my avitar, since 1978. The transmission is still working flawlessly. I can't remember all the numbers anymore, so I looked up a link for you. http://transmissionrepairguy.com/transmission-temperature-gauge/ Bob
You mentioned the top of the trans was dry near the vent tube... but is the vent tube venting? Mud dauber plug it? If that vent is not open, pressure is going to go somewhere, like dipstick tube possibly.
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