I have ~170K miles on my 2010 Golf TDI with a 6-speed manual transmission. My car shifts great, but I wonder if maybe I should do the change? My previous car, an amazing 1995 Mercedes E320 Special Edition, took a crap when I had the automatic transmission fluid changed at 100K. I know automatic transmissions are different than manual transmissions, so maybe there should be no worries.
auto trans are completely different than a manual Gearbox in terms of lubrication. It's more comparable to a differential drain and fill than an automatic transmission.
An auto trans lubricates like your engine. Where it has a pump and pressurizes fluid throughout the valve body. These crevacies inside of the valve body and lube system in an auto trans, build up sludge overtime that can possibly loosen overtime and plug up one of the crevacies. That's why it's not uncommon to hear that after a trans flush the trans went out shortly after. This is due to the fact that people tend to do them after the vehicles driven over 100k miles, allowing for the sludge to develop in the first place and get loose after a flush.
Whereas those who do flushes frequently from when the vehicle was new, rarely have trans failure.
A differential and manual gear box lubricates by sloshing the oil with the gears. No pump, complex crevacies etc to get sludge stopped in. Also gear oil which is most commonly used in a manual Gearbox, doesn't sludge like ATF which is a much thinner fluid. Note, some differentials call for ATF..aka Toyotas from the 80-90's...which is dumb if you ask me
It's good to do, to see if you have any metal shavings etc. Also, you have to remember that the wear happens gradually. So unless you have some catastrophic issue, rarely does one notice that there's a decrease in performance as it happens slowly...think of brake fluid.
Change that fluid and fill her up, don't be surprised as to the pleasurable difference in shifting
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