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Poly Mounts + Rubber Mounts = Problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Liberator, Jan 29, 2003.

  1. Liberator

    Liberator 1/2 ton status

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    The problem: Broken transmissions/adapter plates repeatedly and too often. Third tranny and second adapter plate to be exact!
    The question: Can using rubber motor mounts and Polyurethane tranny/t-case mounts create enough stress between the tranny and t-case to cause the breakage of the tranny housing or adapter plate under high-load conditions?
    Any suggestions to fix the problem or insight will be greatly appreciated!
     
  2. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    Use all poly..... /forums/images/graemlins/wink.gif
     
  3. imiceman44

    imiceman44 1 ton status

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    Like fumes said, use all poly.
    You would limit the movement.
     
  4. DesertDueler

    DesertDueler 1/2 ton status

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    You are always supose to use the same mounts throught. If not things break, like you have experinced. What happens is the rubber mounts allow more flex than the pole mount, so the motor flexs farther then the tranny mount will sllow. Go to all poly, go back to all rubber, or go all out and use solid mounts.

    Dan /forums/images/graemlins/burb.gif
     
  5. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    If you search through my posts (about a year and a half ago) I had this same problem with brand new GM motor mounts and Energy Suspensions poly t-case mounts. I broke the expensive 350/205 adapter pretty good. I replaced the motor mounts with the ORD semi-solid ones with poly bushings (as well as keep the poly t-case mounts) and have not had any trouble yet (even while truck pulling)........:knocking on wood:.

    Go all rubber or all poly. Mismatched mounts will "fight" each other due to differences in give.
     

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