Question: I have a 2005 Nissan Titan I purchased new. It's an extended-cab 2WD automatic with fewer than 80,000 miles. It's a daily driver but does not tow, haul, or go off-road. I've mentioned to Nissan's service department that I had concerns about the truck rolling backward on inclines. They told me it was normal, not to worry, and left it at that. Now, I notice that I can't shift with the +/- shift button on the steering wheel. So I tried the actual shifter, but the only gears working were P, R, N, D (OD, 3, 2, and 1 are all inoperable.)
I took the truck to the Nissan dealer who said it would cost $100 to test, so I gave in and paid them. Results came back that the valve housing was broken and would cost $1500 to fix. I asked if that's why the truck rolls backward, and they said it would be more money to look into the transmission further. They questioned me some more about the truck, and I told them I just had the transmission flushed and the fluid was a burnt red color. They said a clutch might have burned up the oil and caused the truck to roll backward. I called Nissan customer service and was told they are not responsible outside of warranty. I wish I had bought a Ford, Chevy, Dodge, or Toyota.
Answer: The valve housing they're referring to is also called a "control valve assembly." It's mounted at the bottom center of the transmission and visible when you drop the drain pan. In the old days, it was known as a valve body with lots of hydraulic valves, springs, and check balls. Today's electronically controlled transmissions use computer-controlled solenoids to command most pressures and shifting. So the control valve assembly is pretty much a valve body full of solenoids.
As far as your gear engagement problem is concerned, I have to assume the technician was correct with the diagnosis, since checkout typically involves a scan for trouble codes and a few quick functional tests. Your limited powertrain warranty had an expiration date and mileage; therefore, the manufacturer is not responsible past that point. I did see the term "flush" in your question, and we have come across several occurrences where outside shop flushing procedures may have instigated a transmission failure. Also, Nissan has published a list of special transmission fluids to be used on specific units -- voiding the warranty if not complied with. Burnt red transmission fluid? Fluid from a truly burned transmission is almost black with a very strong odor.
Getting back to the rolling backward condition, your best bet would be a side-by-side comparison with the same truck. If the condition was there since day one, it may be normal. Pretty much any car or truck with an automatic will roll back if the grade is steep enough. What actually determines the rollback is engine idle speed and transmission stall speed. We can assume idle speed is correct (it's computer-controlled), but you can do the stall speed check yourself. Simply engage the parking brake, apply your left foot firmly on the brake pedal, put the transmission in Drive, and depress the accelerator pedal until the tachometer reaches its highest point. Then repeat the process in Reverse, not applying the gas for more than 5 seconds each time, and let the engine idle for about 10 minutes to cool down the transmission when done. The tachometer should've peaked between 2500 and 2800 rpm. Further diagnosis is warranted if above or below that point in Drive or Reverse.
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