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BBC 454 and TH400 question / Problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by reddog64, Apr 16, 2002.

  1. reddog64

    reddog64 1/2 ton status

    Nov 9, 2000
    Likes Received:
    Federal Way, Washington
    OK.. apparently my BBC 454 puts out too much torque and caused my torque converter to baloon out and take out the thrust bearing... my crank now has .125 end play, the recommended tolerance is .006 ... I have 1/8th an inch play...

    What torque are yout bbc guy's running...
  2. nvrenuf

    nvrenuf NONE shall pass! Premium Member

    Jan 7, 2002
    Likes Received:
    Mobile, Al.
    **I must be honest and say my TH400 is currently broke (planetaries?) and I'm too poor to fix it so I'm currently running a SM465 BUT I have had a TH400 for many years and will again as soon as my money tree blooms**

    I have a BBC in my truck and according to my "Desk Top Dyno" program it's pushing 446 hp & 496 ft lbs. I have abused mine for years at mud bogs, 4 wheeling and on pavement without any complaints (until recently). I've never had a balloning problem with my converters (I've run a tight 2200 and a loose 3800 - both J.W. Performance brand). I've always associated ballooning problems with heavy nitrous applications, are you using nitrous? No offence but is your converter a quality part? We all know that cheap can (but not always) equal JUNK.

    The thrust bearing being damaged makes me question if the converter was completely seated into the pump at installation. If it wasn't seated (which is easy to do) then that could cause a pressure on the crank and damage the bearing. Also, has that motor ever had a manual trans on it? A really stiff pressure plate can also hurt the thrust bearing. If it has had a manual then the thrust problem may have already been there but gone unnoticed until the current failure.

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