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Scarry noise at idle Sounds like something in the trans? HELP!!!

Discussion in 'The Garage' started by foxman, Jan 5, 2004.

  1. foxman

    foxman 1/2 ton status

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    Ok My 88 K5 (700r4) has developed a noise that sounds really weird. At Idle it almost sounds like a bad water pump (bearing cocked and whirring like the belt is slipping on the pulley) When I tried to identify the sound, I followed my ear to the bell housing under the truck. It seems the most loud there. Here's the scarry part: When I turn the truck off, the wirring turns into what sounds like a balloon when you streach the inlet to make a high pitched noise, and then it slowly dies off. Almost sounds like an air pump or valve of some sort letting out preasure. I did eliminate the air pump and disconnected the steel air lines and valves going to the exhaust manifolds but I left the steel connecting line that runs behind the intake there. Does that steel line have any link to the intake manifold or something that I'm not seeing?

    I'm thinking that what's wrong has to be vaccum related or some type of pump I'm not fimiliar with (Trans?)

    Any help on this would be greatly appreciated. Thank you




    Jeremy
     
  2. TruckNutzDude

    TruckNutzDude 1/2 ton status

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    I have had a few noises develope in my Blazer lately. One of them I thought was a bad water pump but turned out to be a mount for the starter wire rubbing on my harmonic balancer. I also had a transmission pump go once. It didn't make a lot of noise that I noticed. The tranny just started to not work so well and a friend of mine fixed it since I konw nothing about automatics. Good luck finding the problem, I hope it's something simple that just got over-looked /forums/images/graemlins/wink.gif
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds like maybe your vacuum brake booster isn't holding vacuum after you shut the truck off, and the torque converter bearings/bushings are going.

    Does the "transmission" noise go away when it's put in gear?

    Of course those are just educated guesses, the brake booster is the only thing that is easily tested. (do you have brake assist for 2-4 pumps after the truck is turned off?)
     
  4. 99firehawk

    99firehawk 1/2 ton status

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    easy way to tell if its engine or trans, crwal under the truck and un hook the torque convertor from the fly wheel and start the truck. Noise still there its in the engine, its gone its on the trans. But im gonna have to go with the booster.
     
  5. K05Aggie

    K05Aggie 1/2 ton status

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    That sounds exactly like a problem I had. Unfortunately I never figured out what it was. I've had the transmission rebuilt and got a new torque converter and flexplate since the noise started. I also took apart the oil pump, but it looked fine and the oil pressure is great to this day.

    My solution was this: keep driving it. It went away for the most part after about eight thousand miles.

    It only occured when the engine was hot and usually only when it was in gear, especially at idle. I could usually get it to go away by revving the engine.

    I believe the problem is in the engine because it was gone for two thousand miles starting the day I changed the oil.

    timeline:
    put in synthetic blend oil
    2000 miles later: noise starts
    1000 miles later: change back to regular oil, noise gone
    2000 miles later: noise back, changing oil has no effect
    7000 miles later: noise occurs less frequently and eventually goes away
    1000 miles later: change oil, noise back for 500 miles
     
  6. foxman

    foxman 1/2 ton status

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    the "trans noise" doesn't go away in gear, but it only is noticable at an idle and sltghtly above. I do however hear a whistle coming from the engine compartment at idle and slightly above. I'm betting that there's a vaccum leak somewhere I can't see. The whirring noise and preassure let off noise began happening at the same time, so I'm guessing that what ever it is is doing both things. It feels about 10 below today so I don't think I'll have the urge to get under there and disconnect the trans today...

    ...Just hoping someone has had this same prob before and fixed it in 10 minutes for 5 bucks, and didn't get dirty in the process, and on top of all that doesn't mind telling me how to do it. /forums/images/graemlins/grin.gif

    The trans was rebuilt @ 4000 miles ago so I wouldn't guess TC bearings. I'll do the brake booster test today to find out bout that one...


    Still searching for clues in MI....



    Jeremy
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    If it also does it under load, doesn't sound like the converter...usually once it's under a load, the noise will stop.

    Only one or two "vacuum reservoirs" I can think of are the brake booster and MATBE one of those vacuum "balls" sometimes used to control AC vents and so on. Don't know that trucks used them or not, I know cars did. Still, sounds more like the booster.
     

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