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203 front shaft to driveline bolt size

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by SummitXMK, Dec 4, 2001.

  1. SummitXMK

    SummitXMK 1/2 ton status

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    I sheared my 203 to front driveline bolts. Does anybody know what size these are. Also do they need to be grade 8? They are also fine thread I think. Will I have to get them from someplace special? Thanks for your help as always!!

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  2. zakk

    zakk 1/2 ton status

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    mine are grade 8. i got them from home depot.

    -zakk

    '77 1-Ton K5

    [​IMG] CK5's MOAB 2002 OR BUST!! [​IMG]
     
  3. SummitXMK

    SummitXMK 1/2 ton status

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    Do you remember what size they were? Fine or course threads? Thanks alot!!

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    The head is 1/2 so I think that would be a 7/16 fine thread.
    Actully I ran across a discussion on another board about a guy who runs ungraded bolts so it will shear to hopefully prevent blowing the u-joints and axle shafts in the front axle. Neat Idea. My only concern would be if the threads in the flange were damaged when it sheared. and fishing them out. I guess you could carry a spare flange and worse come to worse it could be swapped.
    Grade 8 would work fine. Grade 5 is probably more than strong enough.

    Women dig dents and flat paint!
    coloradok5.com/gallery/Grim
    75 Jimmy, Dollar
    Grim-Reaper
     
  5. SummitXMK

    SummitXMK 1/2 ton status

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    Well mine sheared at 35 mph and the driveline went right into the back corner of my transmission and destroyed it!!!! I mean it really destroyed it!! So you might want to take that into consideration!!!

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  6. Wheels

    Wheels 1/2 ton status

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    7/16" diameter with a 5/8" hex head 1' long. Grade 5 works well but find out what caused them to shear.
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Hmmm good point. I guess if you were to run it like that there would need to be a drive shaft loop or a gard installed to protect the tranny. I'll see if I can find that post on the POR board and let him know what you had happen.
    You still running fulltime? I would check the drive shaft for problems and check your pinion angle. With a CV drive shaft that pinin needs to be in line with the shaft. If it's not it will cause vibrations and that may be the cause of it shearing the bolts.
    Another problem might be the CV needs rebuilding or it's running at too much of an angle and binding under droop. Could have snapped a bolt last wheeling trip and then spinning fast on the road took the rest out.

    Women dig dents and flat paint!
    coloradok5.com/gallery/Grim
    75 Jimmy, Dollar
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  8. SummitXMK

    SummitXMK 1/2 ton status

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    Well I was letting my little brother drive it and he said it had a slight vibration so I picked it up to take it home and check it out. My guess would be that when he changed the front u-joint (that was part of the deal to borrow it) he didn't tighten them enough so that is why they sheared. Because it was a bad vibration when I got it!! I knew I should have stopped but it was like 20 degrees out and snowing. Its like only 3 miles to home!!

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  9. drivelineman

    drivelineman 1/2 ton status

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    5 /16 24 thread 1 1/4 long if its that type and 7/16 14 thread 1" long for the flange type-Jess 530-877-2875

    Owner of High Angle Driveline http://highangledriveline.com
     
  10. michaelm

    michaelm 1/2 ton status

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    are you saying you broke the bolts at the TC end or the dif end of that shaft
    I would not have expected serious TC damage from the top end of the shaft coming loose, but would have anticipated it from the dif end breaking and stuffing the shaft through the case
     
  11. SummitXMK

    SummitXMK 1/2 ton status

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    Those 5 little bolts that bolt the driveshaft to the front of the transfer case sheared and sent the driveline into the rear corner of the transmission. There was no damage to the transfer case.

    78 K5 Cheyenne 400 th350 203 With lots of miles
     

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