Quote:
Originally Posted by truegearhead
Is this really a problem? Do people blow transmissions?
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While not a maintenance item like tires and brakes, it is fairly common to have to replace a transmission. I know several racers who are on their 3rd or 4th transmission.
I will say that its hard to know if the failures are caused by high temps, too many miles, driver misuse, or something else. Personally, I am on transmission #2 and I blame the problems with trans #1 on myself (and some sloppy shifting).
Also, I see a few Spec Boxster's with external transmission coolers so there are some racers concerned enough about temps to try and do something about it. I do not run a trans oil cooler on my car but I do change the trans oil twice per year in the hopes that fresh fluid will provide some protection against heat. Still, I think that I (the driver) am my transmission's worst enemy.
In terms of trans oil performance, my limited understanding is that the trans oil is manufactured to a specification (like API GL-4 or GL-5) and then that spec has a defined test procedure (like ASTM D7450 or similar). I haven't done the research but you're likely to find the upper temp limit in those types of documents since all of the manufacturers just quote compliance with the spec's and rarely actually publish the numbers. With Porsche, it might even be more complicated since they might have their own spec which goes above the standard industry spec's (again, I don't know this for sure but its not unheard for Porsche to do something like that).