A4xn transmission noise in park

1996 FORD TAURUS
137,000 MILES • 3.0L • V6 • FWD • AUTOMATIC
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THANKYOUSE
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I have been doing general mainenace on our old family car (96 Taurus). This car has had previous transmission work done on it although I do not know what, as it was not in my possession at that time. The car is currently up on jack stands with all 4 wheels off. One of the rear brake calipers is removed so it is undriveable for testing right now. I brought the car in due to known various vacuum and coolant leaks. While removing one of the coolant hoses I disconnected the transaxle wiring harness connector (located on top of the transaxle next to the transmission range sensor) to gain a little more room. When I did this the whole assembly came out rather than the connector disengaing. The wires got a yank but nothing extreme. I popped the whole assembly back in and left it alone. After running the engine for testing after the repairs, I noticed a noise that I thought was a vacuum hiss from a leak I missed. After further inspection I was able to determine that the noise was in fact coming from the transmission. I have only been running the car in park and noticed that this noise only happens for about a second or so during quick 1000 rpm increases or higher. It sounds much like a zipping noise similar to a zipper on a coat. I do not know if this was a noise that existed and I overlooked before I started repairs. It is semi likely that it was. What could this noise be and could it have been caused by the yank on the wiring? If a new transaxle may be needed this car may be headed to the scrap yard right as I'm finishing putting about $300 in parts into it :(
Any help would be appreciated!


Oct 28, 2014 at 11:02 PM
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CARADIODOC
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Before you get overly concerned, that noise might be normal. Can you hear it from inside the car with the windows rolled up? If it only lasts a few seconds, it's not due to something rubbing like the wires on the socket. You may be hearing a solenoid activating. I'm much more familiar with Chrysler's computer-controlled transmission. They were the first to have that in '89. They make a ratcheting or buzzing noise when placed into "drive" or "reverse", and when slowing to a stop. One of the shift solenoids cycles on and off dozens of times per second rather than simply switching on or off. That's called "pulse-width modulation". While the valve turns on completely, then off completely very rapidly, the overall average is to allow fluid flow and pressure to build up relatively slowly. That produces a cushioned engagement for comfort.

You may also be hearing a pressure relief valve opening up. With increased engine speed, the transmission's pump is running faster and the increased flow can allow fluid pressure to build up faster than it leaks out of the normal places. That pressure may need to be limited, again, for comfort when a gear is engaged.

I wouldn't lose any sleep over this until you have a chance to drive the car.
Oct 28, 2014 at 11:53 PM