In my experience NVH, (engineering speak for noise, vibration, and harshness) is one of the more time consuming and difficult diagnostic situations. The manufacturers work extremely hard at ensuring that their automobiles have as quiet environment as possible inside the passenger compartment. They have to contend with road noise from the tires, air noises while the car is at speed, mechanical noises from the operation of the engine, driveline, and other components, noise due to weather, harmonic vibrations from various components, and increasingly sensitive consumers.
He described how the transmission was rebuilt but soon came back with a noise complaint. When he inspected it he noticed that upon initial startup he could hear no noise, but after 20 seconds or so the noise occurred while the vehicle was idling in either Park or Neutral. When he placed it into gear the noise went away, but as soon as the vehicle began to move the noise returned. As the transmission shifted the noise lessened, and by the time he reached third or fourth gear the noise was no longer present. He also noticed that every once in a while the vehicle would try to stall when coming to a stop.
Thus is the case with the 2000 Crown Vic that showed up at one of our installers. With the car having 190,000 hard miles and needing an exchange unit installed, the Young Guy (technician) quickly pulled the unit and dropped in a fresh 4R70W reman. It all went smoothly until the test drive.
Noise is one of the great mysteries of the transmission world. Noise is subjective, and people rarely can interpret noises in the same manner. Noise travels much faster and farther in solid objects such as the steel of an automobile than it does in air. There is driveline noise, engine noise, suspension noise, exhaust noise and road-generated noise.
Continuing with our third article in the series on manual-transmission diagnosis, we now concentrate on noise. Noise is a difficult and time-consuming problem if you do not follow a prescribed step-by-step diagnostic process. Every rotating or moving part in a vehicle creates some noise. The vehicle itself moving through the air creates noise. Tires, exhaust, and suspension parts create noise as part of their normal operation.
One of the toughest things in the transmission industry for any technician to diagnose is a noise problem. It’s even tougher to diagnose over the phone, and at times near impossible. In some instances, as with the 5R55S/W transmission, there can be several different things that can have you chasing a noise ’til you’re about to pull hair from your head.
The 4T65-E was introduced in 1997 in several vehicles equipped with the supercharged 3.8-liter engine, and some non-supercharged 3.4- and 3.8-liter engines. It was considered to be the big brother to the 4T60-E transaxle.
Our instructor began by teaching us that a simple planetary gear set consists of 1) a center sun gear, 2) a carrier with three or more pinion gears that are free to rotate on their pins around the sun gear and 3) the internal ring gear, which meshes with the pinion gears. Then he started to say, “If you hold the internal gear stationary and drive the sun gear, you will see the pinions drive the carrier in the same direction as the sun gear but at a reduced speed with increased power.” This is where some of my fellow classmates started to get bored.
By this time, I guess you’ve figured out that this article has to do with noise. I’m sure many of you reading this have your own noise-related horror stories. Noises are difficult to diagnose when you’re standing right there; on the phone, they’re next to impossible. (Have I mentioned that I hate noises?)
A four-wheel-drive 1995 Dodge R1500 pickup was towed to a transmission shop, which performed the usual pre-checks, including checking codes, cooler flow, pressure, and function of the transfer case and both differentials. All preliminary checks pointed to the transmission as the problem, and its subsequent removal and inspection did verify a defective transmission. The transmission rebuild seemed to go routinely, and the transmission performed adequately on the road test.