What causes the transmission to go bad in an '07 Nissan Maxima and whe

Transmissions normally go bad due to lack of maintenance by the owner. This includes inspecting for leaks which could be noticed not only by a visual inspection of the entire exterior of the transmission and its external components such as the hoses going to the radiator or its own oil cooler but by regularly checking the dipstick for the correct fluid level according to the owners manual.

Although cars these days have very long fluid change times such as never or every several years, the purpose of extending the service life of wear and tear items is to lower the overall average cost of maintaining a vehicle which has proven to be a huge mistake by making car owners believe they need to do less maintenance on their vehicles.

When inspecting the fluid level you would also inspect the fluid color as the fluid gets darker it is also showing signs of internal wear. If the transmission has a serviceable filter to be changed on occasion and the oil pan needs to be removed, you would inspect the pan area internally for metal shavings and small pieces of clutch friction material. Transmissions are not built to last forever but they should last a long time.

Driving hard such as racing, towing a heavy load, shifting from R to a forward gear while still in motion in R, etc, will also prematurely wear out the transmission and will require more preventive maintenance than normal. Sometimes, the simply break on their own due to less than perfect parts being used when built new at the factory. Other times when maintenance was completed, cheap parts were used that don’t last very long also.

Keeping a regular scheduled preventive maintenance program with your vehicle is only a good thing, my vote is change the fluid, 100% by inline flush method to include the cooler, with OE fluid, every few years which may equate to every 60,000 miles.