What does a transducer do?

[jwfab1]

I have an 01 Silverado Z71 and I have a squealing sound coming from the tranny or the transfer case. I was told by the owner of the dealership that this was probably the transducer for the cruise control or the speed, which will require changing the dash speedo, thus a huge headache at the DMV. But the truck isn't in cruise control when it is doing it. It will however stop when placed in 4HI under power. As soon as I let off the power it comes back. They just replaced all the bearings and seals in the transfer case, which took 30 days to do, so he says it's not from there. Anyone ever have this problem?? I left the truck there again and they are going to further investigate. After mentioning the dash replacement, I told him he would have to do all the paperwork, he offered to buy the truck back, including tax, licensing, doc fees and the flowmaster that I just had installed.


Jason

[Kritter]

a transducer converts something mechanical to an electrical signal and then goes into a "blackbox" for computations and that spits out an output...could be a pressure tranducer, a speed tranducer etc..

http://www.csupomona.edu/~kranderson1/ME435L/ME435_LABMAN_WIN03.pdf

go to page 8 of that for a break down of a pressure transducer...my old lab manual!

[matt_helton]

im a bit confused by your question. does the owner of the dealership you took it to have any mechanical knowledge??? cus the owner of my work dosent. is the "squeeling" noise constant, under acceleration, decel or what??? iis it a loud noise, or quiet noise??? it sounds to me like they are giving you a B.S. story. there is a speed sensor on the t-case that sends a signal up to the PCM and the BCM to control everything. the cruise control and module is under the hood on the fire wall. if its a trans noise i would think it would be a pump noise or something major and or pretty easy to diagnose. "squeeling" noises also comonly come from drive belt accessories, like alt, ps pump, ac comp, tensioner, idler, air pumps, water pumps and so on. as far as changing the cluster, there is not a big deal there. we do them all the time at my work, we send them out to a GM approved remanufacturer called AER, and they just calibrate the new odometer to the mileage as it was on the old one. their are NO dmv hassels. give me some more info about all the circumstances in which the noise occures and the exact type of noise and ill see if our tranny guy has any advice.

[jwfab1]

The sound is a high pitch squeal, simular ta a bad bearing. But all of the bearings in the transfer case have been replaced. The dealership had my truck for 30 days, and for about 20 of them they had no idea what the problem. They narrowed it down to transfer case after doing a sound test. When my truck was returned the squeal was still there, so I went back for a third time, where the owner went for a ride with me. Along with the service manger and the used car manager.

The squeal is constant in 2WD above 35 MPH. In 4HI the squeal is gone when power is applied. Comes right back when power is removed.

Jason

[matt_helton]

ok, lets get something straight here. is the noise coming from inside the cab or under the truck???? i dont follow you on the whole dash cluster replacement thing. if thats what they say is the problem then why dont they fix it. i dont think we are gettin all the info here. back to the noise, if its under the truck and they have ruled out the x-case as the source i would look at your drive lines, maybe a u-joint noise, front or rear shaft. possibly a front diff problem as well. its real hard to make sugestions with out actually hearing the noise and or driving the truck. and im real surprised they offer to buy the truck back that easily since its 3 years old, unless this has been an ongoing problem that they havnt been able to correct after many attempts. have you tried getting a second opinion from another dealer??

[jwfab1]

Matt,
The sound is from outside the cab under the truck near the tranny / transfercase.

The dash replacement I thought was going to be a headache at the DMV so I told Norm, the dealership owner, that he was going to be responsible for taking care of the paperwork. He told me it would be my responsibility. I just found out that the new cluster could be programmed by AER to the exzact mileage of the old cluster, so no problem with the DMV.

As far as the drivelines, the front shaft was disconected and the noise persisted. Thus eliminating the front shaft and the front diff.

This is an ongoing problem, the third time the truck has went back for the same problem.
1st time truck was returned to my wife and she was told there was no problems.
2nd time I took the truck in and they replaced the front diff actuator and the front transfer case was rebuilt. This took them 30 days to complete!
3rd time Norm, the used car manager, and the service manager all 3 went with me for a test ride. Norm then suggested that the problem was the transducer or the speedo. I told Norm that since he has exhuasted all his options, that I wanted to take the truck to another dealership for a second opinion and have him foot the bill. He told me no, that he wasn't going to pay another dealership for any work. If i wanted a second opinion that I would have to pay for it.

After picking the truck up on the SECOND attempt it was returned to me with the fuel light on, it had 1/2 a tank when dropped off. When I took the truck back for the THIRD time I made sure the fuel light was on, I was going to return it to them the way they did to me. The technician came to me and informed me that running the truck with the fuel light on could damage the fuel pump. I replied, " thats funny, thats the way I picked it up from you guys." He responded," I know, we do that so that the trucks don't get stolen." I asked, "so you siphoened the gas out of my tank, where is my gas?" He told me, "we're not responsible for putting gas in customers vehicles." Can you believe he was that ignorant???

I told Norm about this before leaving in the rental and he assured me my trucks tank would be full when I pick it up, for the inconvience.

Jason

[tim_krueger]

I'd sell the Chevy and buy a Ford! lol

[FABRICATOR]

One thing “transducers” don’t do is make noise. They are made of plastic, have a small magnet with a copper coil inside; no moving parts. Most are about the size of an automotive cigarette lighter. If one did contact a moving part it could only make noise for a few seconds before getting chewed up.

Does your truck have a 2 section rear driveshaft with a center support bearing? These bearings can make a lot of noise when bad. Have they checked for vacuum leaks around the intake manifold, they can be very loud? You can do this by spraying small amounts of ether (starting fluid) around the area at idle and listen for a change in idle speed. Is the exhaust system rubbing on anything? These are things you can do at little or no cost. The transmission and transfer case are no more likely to make this kind of noise than those things mentioned above. If the noise is present in 4WD, no load, as you stated, then they should be able to witness it while up on the hoist. This should pinpoint the problem in seconds. Hmmm, let us know what you find out.

[tedmales]

you said it quits making the noise in 4 wheel drive when you give it gas, but when its coasting does it come back? could be a backlash problem in the transfer case? did you try to put it in 4 hi with the front drive line removed. if you did and the noise went away even with the drivline out i would still say it was the transfer case. maybe!! if you could find someone with a chassis dyno and put it on it and run it and then look under the truck. or even on a lift . i wonder if it make the same sound while not under a load.. maybe put it on jackstands and then put it into gear if it make the noise then you should be able to look for it, but be way carefull.

[jwfab1]

I forgot to add that this truck has a 6" Pro Comp lift, if that would help.

Fabricator,
The noise is definately from around the tranny / transfer case area. So intake manifold is out of the question. They have ran it on the hoist but it still wasn't distinct enough. Not only that, the transfer case made alot of noise, I was right there, and I asked about it and was told thats normal. It is just the transfer case "floating" or "unloading" is what they said.

Tedmales,
Yes the noise comes back when I let off the gas. That makes sense, but the transfer case is also live in 2WD and the sound is there regardless if on the gas or not.

The mechanics put my truck on the lift and ran it with and without the front shaft in. In 4WD and 2WD and the sound was still there, thats what they told me, I wasn't there for that test.

I appreciate all the help guys, if anyone has any other opinions please express them. I really want to get this matter resolved.

Glad to know that the TRANSDUCER isn't another part like the KAHOOTER VALVE, lol.

Jason