Shift Pointers
- Author: Pete Luban, ATSG Technical Supervisor
Whenever I get a call slip here at the ATSG hotline and the call tag says “NOISE,” I immediately feel the need to leave for vacation.
I remember test-driving a station wagon (they’re called crossover vehicles these days) with a complaint of a whistling noise that began around 40 mph and got louder the faster you drove. It turned out to be a rotten roof rack that became a flute.
Then there was the time a job was sold on this whining noise that eventually turned out to be bad bearings in the turbocharger. Did I mention that I hate noises?
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?)
So a customer brings a 1999 Grand Am into this shop with a complaint of a noise during braking and also said he had been to another shop, which had replaced an axle and the serpentine belt, yet the noise remained.
The car was now taken for a road test, which confirmed that the noise was present at low speeds during braking. The technician also determined that turning the steering wheel eliminated the noise.
It was decided that the right front axle bearing was the cause of the noise, so one was ordered and installed. The car was taken for a road test after the repairs were completed, and the noise remained the same (is that a Rolling Stones album?). It still sounded like a right-front axle bearing.
After some series road testing during which the shop’s technician tried to pinpoint the source of the noise, an odd thing was noticed.
This car was equipped with Goodyear Eagle LS 16-inch tires (see Figure 1). These tires have a raised cosmetic rib that’s very close to the wheel rim (refer to Figure 2). This rib was chafing the wheel rim and creating the noise – which, by the way, has no effect on tire performance or safety.
Maybe a different tire/wheel combination would have eliminated the noise, but in this instance the fix was to raise front-tire pressure to 44 psi (303 kPa). Have I mentioned that I hate noises?
This next problem is a good example of how a noise in an unrelated area causes a vehicle to end up in your transmission-repair shop. A 1999 Chevy pickup came into the shop with a complaint of a noise during upshifts around 1,800 rpm. On the initial road test, the technician determined that the noise was not coming from the transmission; however, the shop, not wanting to lose an opportunity to increase the bottom line, decided to take on this noise issue.
The serpentine belt was removed, the vehicle was given a short road test and, lo and behold, the noise was gone. The belt-tensioner pulleys did not look too good, so the belt and the pulleys were replaced. The truck was road tested, and the noise was gone, so it was parked, awaiting delivery. The service writer now took the vehicle for a road test (good move) and came back to the technician with bad news – the noise was back!
The long and short of it is, after further diagnosis the cause of the noise turned out to be the heater hoses. It seems that the hoses had become soft and made contact with the engine (see Figure 3), causing the heater core’s metal wire mesh to vibrate and sing right around 1,800 rpm. Fabricating an insulator for the heater hoses fixed the problem.
Have I mentioned that I hate noises?
Many thanks to Robert Martin for sharing his experiences with me.
