88 Country Squire makes loud humming noise at highway speed

Discussion in 'General Automotive Tech' started by DynamoSquire, Dec 22, 2017.

  1. DynamoSquire

    DynamoSquire New Member

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    My 1988 Ford Country Squire recently started making a loud hum from the rear of the car when accelerating over 65 miles an hour. The noise only happens when holding the accelerator, and will stop roughly 2 seconds after releasing it. The noise only happens when holding the pedal, so I can roll down a hill at say 75 miles an hour and only pressing the gas pedal will make the noise appear.

    I suspect its something with the transmission but am not sure.

    Engine is a fuel injected 87 5.0 with a 4 - speed ford AOD
     
  2. 63Fowagon

    63Fowagon Active Member

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    Check your rear differential oil . Sounds like a rear end noise . Rear axle noise when coasting not under load of accelerator .
     
  3. Silvertwinkiehobo

    Silvertwinkiehobo "Nothing is foolproof as fools are ingenious."

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    Yes, check your diff level, and check for evidence of fluid leakage.
     
  4. Grizz

    Grizz Are we there yet???

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    U-joints? Jiggle the drive shaft?
     
  5. Silvertwinkiehobo

    Silvertwinkiehobo "Nothing is foolproof as fools are ingenious."

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    U-joints make noise all the time. The fluid level and fluid condition both need to be looked at, and whether there is slop and damage to the internals.
     
  6. DynamoSquire

    DynamoSquire New Member

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    U joints are decent shape from what I can tell. Got a chance to go under the car today and the there's some minor leakage around rear differential cover, so I suspect it might be fluid (or rather lack there of) issue. Going to get a new gasket/change the fluid out after the holiday and see if that fixes it.
     
  7. Silvertwinkiehobo

    Silvertwinkiehobo "Nothing is foolproof as fools are ingenious."

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    When you do it, there's an area under the ring gear that collects metal bits if the gear teeth begin to chip. And check to see if the cover has a magnet on the inside; clean it if it does, to see if there are chips or shavings on it.
     
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  8. Grizz

    Grizz Are we there yet???

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    This was one of the first things I did. There wasn’t any noise, maybe some minor leaking but there was a chrome replacement cover at the shop that just so happened to fit. Get a chrome one! I think the cover and bolts can be bought fairly cheap
     
  9. KevinVarnes

    KevinVarnes Well-Known Member

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    Check to make sure there isn't a trail of fluid from the pinion back to the bottom rear of the diff. That would indicate a pinion seal. Either way it sounds like a good time to refresh the fluid. Make sure you add limited slip additive if you have a Trak-Lok rearend.
     

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