84 Fleetwood driveline vibration
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 84 Fleetwood driveline vibration in Past Cadillac Vehicle Discussion; so, when I let off the throttle at 55mph or higher, i get a vibration. car drives pretty smooth otherwise, ...
  1. #1
    acerulz1 is offline Cadillac Owners Member
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    84 Fleetwood driveline vibration

    so, when I let off the throttle at 55mph or higher, i get a vibration. car drives pretty smooth otherwise, driveshaft is perfectly balanced by a reputable shop, u joints are good and mounting is all good. the car is lowered, and my pinion angle has been adjusted to match the transmission angle (both are at 2 degrees opposing each other). any ideas?

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    csbuckn is online now Cadillac Owners Master
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    Rear ends will vibrate when they are getting loose and worn out.
    The Ape Man and The Ape Man like this.

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    jayoldschool is offline GM RWD V8 addict
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    Re: 84 Fleetwood driveline vibration

    Since you say that everything else is good, I'll guess pinion bearing in the rear end.

  5. #4
    Cadillac Giovanni's Avatar
    Cadillac Giovanni is offline Cadillac Owners Enthusiast
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    Re: 84 Fleetwood driveline vibration

    Yeah, my '89 did this a few weeks before the diff gave out. I had a whole new rear axle from a mint donor car, so I just drove it 'til it died.

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    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: 84 Fleetwood driveline vibration

    Sometimes the rear brakes will even vibrate a bit when axle bearings are ready to puke oil.

    Load sensitive like described usually points to driveline but slack side of fan belts fwapping around or even a worn out radiator fan clutch can vibrate in a way that fools.....

    Another strange one is aftermarket exhaust or exhaust system missing mountings.

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    acerulz1 is offline Cadillac Owners Member
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    Re: 84 Fleetwood driveline vibration

    hmmmm, looks like I'm gunna havta take a look at the diff, i suppose. doubt its gunna be anything to do with the belt drive system cuz its all new. replaced everything new when I put the engine into it (350 out of an iroc z LOL) I know my exhaust is resting against the trans cross member, but thats a totally different noise. I'm putting the car on the lift tomorrow morning at work to do some work to it, will post what I find! Thanks for the replies so far!

  8. #7
    csbuckn is online now Cadillac Owners Master
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    What year iroc did the motor come out of?

  9. #8
    acerulz1 is offline Cadillac Owners Member
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    Re: 84 Fleetwood driveline vibration

    bout an 88 or 89

  10. #9
    csbuckn is online now Cadillac Owners Master
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    Nice. That would make it an LT1, right? Nice. You document the swap on the internet anywhere?

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    acerulz1 is offline Cadillac Owners Member
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    Re: 84 Fleetwood driveline vibration

    no unfortunately its not the lt1. but soon I will be bolting vortec heads onto it, give her that extra lil kick in the pants haha. unfortunately I havent had time to put any of the pics or story online yet.

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    Re: 84 Fleetwood driveline vibration

    I would bet anything that your vibration is caused by the exhaust hitting the crossmember. On my 94 Caprice wagon, the left over the axle pipe is a little too far forward. It touches the rear end. I chased a strange vibe on this car for ages. Three sets of wheels, lots of tires, two sets of shocks, full front end, all brakes. I finally figured it out.

    93 was the first year for the LT1 in the F body. If its a TPI motor, it's an L98. Some IROCs of that era were just TBI LG4s, though. Like an LO3/LO5, just less power/torque (hard to believe that is possible)

  13. #12
    csbuckn is online now Cadillac Owners Master
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    You're right Jay, thats actually what I meant, tuned port. I had a 92 bird, my first real baby. One day I'll get another.

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    acerulz1 is offline Cadillac Owners Member
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    Re: 84 Fleetwood driveline vibration

    ya it was a tpi 350. running tbi now tho. i had the car on the lift today and the pipes are definitely not touching. double checked the driveline angles, went after the pinion, tire balance. was thinking maybe pinion adjustment but normally its followed with a gear whine, so I'm kinda really stumped, but the thing is so annoying to drive on the hiway. thinking on hooking up a switch for the air ride, and run it with no air and see what the vibe is like, and then start increasing the height gradually just to see if its a pinion angle thing still. rather doubt it cuz i got that dialed in pretty good, 3 degrees up on the pinion, and 3 degrees down on the transmission.

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    acerulz1 is offline Cadillac Owners Member
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    Re: 84 Fleetwood driveline vibration

    well, diff checks out ok, tire balance was ok, driveline angles are 2 1/2 to 3 degrees. over 55 it starts vibrating bad, and when I let off the throttle it has a real good shake to it until i put my foot on the throttle a little, then it mostly goes away.thinking possibly pinion angle is too high? gotta get it back in the air when i get a chance to measure the u joint working angle. just about ready to light a match under her lol........

  16. #15
    csbuckn is online now Cadillac Owners Master
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    You measuring the drive train angle in the air?

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