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Cant Figure This Out

This is a discussion on Cant Figure This Out within the General Help forums, part of the LSx Technical Help Section category; 1999 T/A 107k Have a grabbing thunk during forward braking (low speed) and while baking up (no braking applied). Can ...

  1. #1
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    Cant Figure This Out

    1999 T/A 107k
    Have a grabbing thunk during forward braking (low speed) and while baking up (no braking applied). Can feel pedal pulsation or a vibration during forward braking but no degredation
    in brake performance. Feels as if caliper is floating on rotor (noise and
    feel) Also have rattle in front left axle area. Sounds like a rock or rocks
    in a coffee can. The grabbing thunk is only evident during repeated braking over short distances and is not apparent during initial braking or secondary effort. Problematic at any brake temperature. Unknown during cornering. The clunk/thunk is noticable during repeated braking (stop and go) and upon revers gear (w and w/o braking)

    U-joints good, 1/4-1/2" rotational play in driveshaft while in gear, slight
    differential leakage r/s seemingly from pinion seal. Both upper/lower ball
    joints/all tie rods replaced as well as all sway bar linkage. Panhard rod
    looks fine. Outer 2" camber wear on both front tires evident. Remaining tread excellent.

    107k miles on drivetrain. Original shocks/springs. No noticable caliper grab
    or visable rotor stresses (less than 8k on complete brake job minus all calipers). Control arm bushings look intact and within visual servicability.

    No abnormal steering shim or vibrations. Onset of issue is approximately 3k miles.

    Have not checked engine mounts. I ordered a complete Bilstein HD package minus springs as per some recommended posts I have read.

    Can't isolate problem. Thoughts?

  2. #2
    Senior Member ninobrn99's Avatar
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    sorry, its kinda late and i didnt wanna read the whole thing but id make sure your rotors arent warped. i cant remember the coffe can deal right now. its something with the rearend though. Ill search for it over the next few days and get back atcha..

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    Senior Member mrr23's Avatar
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    sounds like the torque arm mount is bad. look at the mount for the torque arm on the trans. pull/push up/down and see if it moves a considerable amount.

    the pulsation is warped rotors. anothe thought is the brake pads sliding when you apply the brakes. they'll hit the bracket from being forced upward from braking. this will make a clicking noise only when you hit the brakes.

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    I will be getting under the car today to check all of what you guys suggested. Really appreciate the assist and will keep thread posted.

    Thanks Again!

    Tom

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    1998 camaro z28

    Quote Originally Posted by mrr23 View Post
    sounds like the torque arm mount is bad. look at the mount for the torque arm on the trans. pull/push up/down and see if it moves a considerable amount.
    great idea. I had one break on my stock lt1 camaro, welded it back together, where it broke again. These things are very weak..

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    The torque arm moves and I can see wear in the bushing/mount. I noticed over the past year the shiftermoves about an inch when I take off in first and/or from stop. Most of my experience is with 67 and 68 Firebirds that I own and this new tech I'll leave to asking.

    Checked with GM warehouse in Willow Run today..no part number for the bushing or bracket. I think I may have to purchase the entire assembly. No big issue as long as this nagging thunk, clunk junk subsides.

    Otherwise..car is phenominal..no problems with 108k on the odometer.

    Again, thanks, and if there are any other areas I should check, let me know.

  7. #7
    Crinkle, Crinkle
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    An inch of movement?

    Better check the engine and trans mounts again.

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    I agree with checking the trans mount. I have found over the years very close inspection, pulling, yanking and lifting sometimes don't work. I had the same issue on my 96 T/a. I went and bought the torque arm assembly (which was crazy expensive for what it is) got under there and took everything about and found out the trans mount was wasted but not in the conventional way. The rubber was still in tact, but smashed, my torque arm could hit the drive shaft "loop/protector thingy ". Took the torque arm assembly back and replaced the trans mount. Problem solved. But I did not have so much noise while braking so you still my have a torque arm problem, but they can have quite amount of slop and still not cause much audible noise.

  9. #9
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    If it helps, I looked at the movement of the shifter upon aceleration and the entire trans (by visually looking at shifter) is moving upwards and slightly frontal (towards engine).

    Like I said before, older cars..no sweat. Looks as if I will be diving in with both feet and treading uncharted territory. I am assuming if mechanically gifted, I should have no worries (Yea) Glad my vacation starts Friday..I'll keep the Visa in hand stock up on beer and keep Dominoes delivery number on the fridge. Car will not be back on road until I solve this.

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