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... BTW, this whole incompressible fluid goes flying out the window when you talk about high pressures. (>2500PSI or thereabouts)
Daniel
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I think you meant to say 25,000 pounds/square inch, not 2,500 pounds/square inch.
2,500 pounds/square inch is a fairly typical pressure for hydraulic systems and has been for many years.
25,000 pounds/square inch is a typical for new common-rail Diesel fuel injection systems, and it's only recently that pressures have been cranked up that high.
Back to the original question: Yes, it's true that transmission fluid expands when it heats up, (and that's true for both automatic and manual transmission oils) but it's a small percentage which for all practical purposes can be ignored.
But you don't have to take our word (or Chilton's) for it; it's simple enough to put a sample in the fridge and in the oven and see for yourself what happens. (don't exceed about 250 degrees F)
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No, I meant 2,500PSI. That is about where things *start* to get strange. It is really *gone* out the window by the time you reach 25,000PSI. Hence the reason it has only been done recently, among other reasons.
Assuming that a fluid (air, liquid, transmission fluid, etc..) is incompressible makes an ungodly set of equations somewhat managable with the use of other assumptions like Newtonian fluid, linear shear force, and about 5-10 others. /ubbthreads/images/graemlins/vomit.gif /ubbthreads/images/graemlins/vomit.gif /ubbthreads/images/graemlins/vomit.gif
Only the past few years has the metalurgy and manufacturing been able to *reliably* produce a system that works at 25000PSI. But a good computer is needed to work the equations that are needed to design the mechanicals of the system (pump, plumbing, fittings, etc).
Daniel