An item that has perplexed me since joining bitog--Please explain why I check ATF at operating temp due to expansion, but motor oil, I do not have to, indicating that it does not expand (as much)---I have read here that ATF is largely a 10W oil base stock. What makes ATF expand more than oil?
Motor Oil doesn't expand with temp, but ATF does?
- Thread starter JDD
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Just going out on a limb here but you're not necessarily measuring ONLY the expansion of the fluid. In a close quarters housing like a transmission as the heat builds up the parts expand along with the fluids. Aluminum drums and housings expand more than carbon steel parts and some plastic/composite parts may not expand at all.
So if you're measuring a unit volume you have to account for the container size also.
So if you're measuring a unit volume you have to account for the container size also.
I think a tranny person (no pun intended) that knows about the works of a transmission would enlighten this subject.
But as a note - I used to service my own transmissions. Remember how some wanted it warmed up then check fluid level. Well I would get the level where I wanted it, park the vehicle on level ground, then next morning before running the vehicle I could pull the stick and see where that level is. I would scratch a light mark (or mental note) on what the level cold should be - so once warmed up, the level was correct.
So anytime later I could see where the level is cold, before start, and could within reason determine if that was close for a warm level.
Here's another ringer - we used to check locomotive diesels oil level with the engine running at idle. It was designed that way. Did it on some ship diesel engines also. On those engines, if you tried to check levels while stopped, you could at times get an inaccurate reading as you don't know if the auto pre-lube pump has just ran before checking which would skew the level as not knowing how much oil was still working down from the upper end. On some of the old large diesels, we hand oiled the upper end with oil cans. Of course those were large slow RPM where I would lay my arm on the rocker arm while pumping oil from a oil can. For stationary gen sets we kept the oil warmed and pre-lubed via timers, and the jacket water warm with some constant circulation. Those we could start and put them to work as they were pre-warmed.
But as a note - I used to service my own transmissions. Remember how some wanted it warmed up then check fluid level. Well I would get the level where I wanted it, park the vehicle on level ground, then next morning before running the vehicle I could pull the stick and see where that level is. I would scratch a light mark (or mental note) on what the level cold should be - so once warmed up, the level was correct.
So anytime later I could see where the level is cold, before start, and could within reason determine if that was close for a warm level.
Here's another ringer - we used to check locomotive diesels oil level with the engine running at idle. It was designed that way. Did it on some ship diesel engines also. On those engines, if you tried to check levels while stopped, you could at times get an inaccurate reading as you don't know if the auto pre-lube pump has just ran before checking which would skew the level as not knowing how much oil was still working down from the upper end. On some of the old large diesels, we hand oiled the upper end with oil cans. Of course those were large slow RPM where I would lay my arm on the rocker arm while pumping oil from a oil can. For stationary gen sets we kept the oil warmed and pre-lubed via timers, and the jacket water warm with some constant circulation. Those we could start and put them to work as they were pre-warmed.
Originally Posted By: Errtt
I think a tranny person (no pun intended) that knows about the works of a transmission would enlighten this subject.
But as a note - I used to service my own transmissions. Remember how some wanted it warmed up then check fluid level. Well I would get the level where I wanted it, park the vehicle on level ground, then next morning before running the vehicle I could pull the stick and see where that level is. I would scratch a light mark (or mental note) on what the level cold should be - so once warmed up, the level was correct.
So anytime later I could see where the level is cold, before start, and could within reason determine if that was close for a warm level.
I did the something similar with my 08 Jeep Liberty. Chrysler decided to save $3 a unit and eliminate the dipstick, creating work for their dealers and tranny shops checking fluid. I made my own dipstick, using one from an older Liberty but found it takes longer than overnight for all the fluid to settle down in the pan. What I found works best was drive for about 20 minutes, park on level ground and let the engine idle for 2-3 minutes. Then use my laser thermometer and get a reading of the pan temp, I aim at the same place all the time. The temp is usually about 160*F-165*F and the level is at the exact same spot each and every time. I had a shop confirm the factory filled the tranny to the proper level before I calibrated the stick.
I think tranny fluid expands slightly, but as already mentioned it probably has more to do with the internal parts of the tranny effecting the level than anything else. JMO
I think a tranny person (no pun intended) that knows about the works of a transmission would enlighten this subject.
But as a note - I used to service my own transmissions. Remember how some wanted it warmed up then check fluid level. Well I would get the level where I wanted it, park the vehicle on level ground, then next morning before running the vehicle I could pull the stick and see where that level is. I would scratch a light mark (or mental note) on what the level cold should be - so once warmed up, the level was correct.
So anytime later I could see where the level is cold, before start, and could within reason determine if that was close for a warm level.
I did the something similar with my 08 Jeep Liberty. Chrysler decided to save $3 a unit and eliminate the dipstick, creating work for their dealers and tranny shops checking fluid. I made my own dipstick, using one from an older Liberty but found it takes longer than overnight for all the fluid to settle down in the pan. What I found works best was drive for about 20 minutes, park on level ground and let the engine idle for 2-3 minutes. Then use my laser thermometer and get a reading of the pan temp, I aim at the same place all the time. The temp is usually about 160*F-165*F and the level is at the exact same spot each and every time. I had a shop confirm the factory filled the tranny to the proper level before I calibrated the stick.
I think tranny fluid expands slightly, but as already mentioned it probably has more to do with the internal parts of the tranny effecting the level than anything else. JMO
Motor oil most certainly does expand. Different vehicles have different check procedures, but most I've owned say you're supposed to check it hot but several minutes after shutdown (to let it all run to the sump). Cold readings are somewhat lower.
Part of the reason for the instruction to check "hot" may be for various reasons:
1/ when systems are actively controlled and cooled, "hot" is a reliably small temperature range while "cold" means a lot of different things between an Alaska winter and a Houston summer. You need consistency when setting or checking a level and "hot" is the easiest way to get that.
2/ "Hot" also means that the equipment was recently used. There may be other factors at play like ensuring that various areas of the transmission are "pumped up" like they should be instead of slowly draining back to the sump or something similar to that. Level checks aren't always simply dipsticks dangling into the main sump - you could be checking the level in some intermediate chamber or something...
3/ "Hot" level is what matters. The fluid levels when in use are what's most important, and where the critical operational factors lie.
Part of the reason for the instruction to check "hot" may be for various reasons:
1/ when systems are actively controlled and cooled, "hot" is a reliably small temperature range while "cold" means a lot of different things between an Alaska winter and a Houston summer. You need consistency when setting or checking a level and "hot" is the easiest way to get that.
2/ "Hot" also means that the equipment was recently used. There may be other factors at play like ensuring that various areas of the transmission are "pumped up" like they should be instead of slowly draining back to the sump or something similar to that. Level checks aren't always simply dipsticks dangling into the main sump - you could be checking the level in some intermediate chamber or something...
3/ "Hot" level is what matters. The fluid levels when in use are what's most important, and where the critical operational factors lie.
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Originally Posted By: demarpaint
Originally Posted By: Errtt
I think a tranny person (no pun intended) that knows about the works of a transmission would enlighten this subject.
But as a note - I used to service my own transmissions. Remember how some wanted it warmed up then check fluid level. Well I would get the level where I wanted it, park the vehicle on level ground, then next morning before running the vehicle I could pull the stick and see where that level is. I would scratch a light mark (or mental note) on what the level cold should be - so once warmed up, the level was correct.
So anytime later I could see where the level is cold, before start, and could within reason determine if that was close for a warm level.
I did the something similar with my 08 Jeep Liberty. Chrysler decided to save $3 a unit and eliminate the dipstick, creating work for their dealers and tranny shops checking fluid. I made my own dipstick, using one from an older Liberty but found it takes longer than overnight for all the fluid to settle down in the pan. What I found works best was drive for about 20 minutes, park on level ground and let the engine idle for 2-3 minutes. Then use my laser thermometer and get a reading of the pan temp, I aim at the same place all the time. The temp is usually about 160*F-165*F and the level is at the exact same spot each and every time. I had a shop confirm the factory filled the tranny to the proper level before I calibrated the stick.
I think tranny fluid expands slightly, but as already mentioned it probably has more to do with the internal parts of the tranny effecting the level than anything else. JMO
I use a IR Laser Thermometer for many things - The wife didn't know what to think when I whipped out the IR unit and shot the deep fried turkey last week. Running that red dot around wore out the dogs too. Its a multi-purpose gadget for sure. Used it just this morning to check the temps on the Harley for a cold morning start - checking things were normal as expected. A great tool to have.
Originally Posted By: Errtt
I think a tranny person (no pun intended) that knows about the works of a transmission would enlighten this subject.
But as a note - I used to service my own transmissions. Remember how some wanted it warmed up then check fluid level. Well I would get the level where I wanted it, park the vehicle on level ground, then next morning before running the vehicle I could pull the stick and see where that level is. I would scratch a light mark (or mental note) on what the level cold should be - so once warmed up, the level was correct.
So anytime later I could see where the level is cold, before start, and could within reason determine if that was close for a warm level.
I did the something similar with my 08 Jeep Liberty. Chrysler decided to save $3 a unit and eliminate the dipstick, creating work for their dealers and tranny shops checking fluid. I made my own dipstick, using one from an older Liberty but found it takes longer than overnight for all the fluid to settle down in the pan. What I found works best was drive for about 20 minutes, park on level ground and let the engine idle for 2-3 minutes. Then use my laser thermometer and get a reading of the pan temp, I aim at the same place all the time. The temp is usually about 160*F-165*F and the level is at the exact same spot each and every time. I had a shop confirm the factory filled the tranny to the proper level before I calibrated the stick.
I think tranny fluid expands slightly, but as already mentioned it probably has more to do with the internal parts of the tranny effecting the level than anything else. JMO
I use a IR Laser Thermometer for many things - The wife didn't know what to think when I whipped out the IR unit and shot the deep fried turkey last week. Running that red dot around wore out the dogs too. Its a multi-purpose gadget for sure. Used it just this morning to check the temps on the Harley for a cold morning start - checking things were normal as expected. A great tool to have.
My guess is they both expand about the same. Maybe it is the depth of the oil in the pan. Trans pans seem to be flatter and wider. Engine oil pans seem deeper. A quart of oil added to the wide pan would not come up as much as a deep pan. That is my guess.
I have wondered about this also.
I have wondered about this also.
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