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Cracked flex plate, how long should these bolts be?

Discussion in 'The Garage' started by kennyw, May 14, 2005.

  1. kennyw

    kennyw N9PHW Premium Member

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    Picked up a '86 GMC Jimmy with a cracked flexplate this week. Finally tore into it and found out why it cracked... there were only 3 bolts holding the tranny to the motor and only one was really close to being tight. Tranny had backed off on one side by 1/8-1/4 inch. So that put the tranny and motor at an angle to each other eventually cracking the flex plate.

    [​IMG]

    Notice the daylight showing between the block and the tranny.

    [​IMG]

    Also found the crossmember with 2 very loose bolts...

    [​IMG]

    Now I need to find 6 new bolts to hold the tranny on with... I think the ones that were in there were too long and did not hold the tranny tight to the block before bottoming out. They look longer than normal... Anyone know how long they should be?
     
  2. sweetk30

    sweetk30 professional hooker Premium Member

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    i dont mean to be rude but if it makes funny sounds it is for a reason. that is bad. i would check the seal at the pump in the tranny for leaks and also all other drive line parts after seeing that.
     
  3. kennyw

    kennyw N9PHW Premium Member

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    I'm gonna be checking everything out while I have it apart. The flex plate is cracked in half for sure and getting replaced. When I put it back together it will have a new input seal in the tranny and output seal in the tcase just because I was in there. The driveshaft is in good shape but I'll be checking the u-joints closely too.

    Somewhere along the line the original 305 motor was replaced with a GM crate 350 (runs strong too) and I suspect they didn't do a great job reconnecting and torquing the bolts between the motor and tranny. They also left off the wire looms on the engine wiring so I have to inspect all of that very closely to besure it has not rubbed thin before I put new wire loom on it.
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    the stock bolts are 1 1/4" long. 1 1/2" is too long and 1" is too short. it took me a few stops because not too many places at the time carried the 1 1/4" 3/8" bolts.
     
  5. kennyw

    kennyw N9PHW Premium Member

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    Thanks, looks like the ones I pulled out were 1-1/2" long.
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

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    hmmmm

    Those numbers on the crank must be casting #!--cant say I've seen them at the flywheel end before!..you can look them up and see what motor the crank belongs in,and if its a steel crank or not..

    I'd check the front pump seal too!--anything thats been that loose to crack the flexplate might have hurt other things--I've seen vehicles like that after "motor swaps" too--they put in only the "easy" bolts,then finger tighten them!--good thing they use dowel pins on the block to align the bellhousing!--many cars and trucks I've worked on had missing bell bolts,and the ones that were there were too long in some cases..more than one vehicle drove in the parts stores lot and I looked at the motor to identify it so I could sell parts to its owner,and the tranny was flopping around,and you could see the flywheel in the "gap" between them!.... :crazy:
     

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