Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Bad Balance Bearing

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Chili 87 K5, Aug 8, 2000.

  1. Chili 87 K5

    Chili 87 K5 Registered Member

    Joined:
    May 8, 2000
    Posts:
    29
    Likes Received:
    0
    Location:
    CO
    Hey gang, I need some advice for my '87 K5! After a high-pitched screech from under the hood, I discovered that my crankshaft was wobbling badly, causing some nasty vibration. I have removed the pulleys from the crankshaft, and have pulled the Harmonic Balance wheel. I have definitely chewed out the oil seal, but I have not yet determined whether there is another bearing to examine. If it's just a seal, I can do that easily enough. Since I don't have the timing cover off yet, my question is; where is the first bearing that I should be concerned about? Is there a separate HB wheel bearing, or should I be checking the front crankshaft bearing? Then, if there is a spun bearing that I am going to have to pull the engine for, should I just get a rebuild kit and go for the whole shot? I've got 116K on this 350, and it has run very well... only a little white puff when I start her up.

    So, whaddya thinks?
     
  2. Blazer1970

    Blazer1970 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,600
    Likes Received:
    0
    Location:
    Old Mission, MI
    There is no separate bearing for the balancer. The front crankshaft bearing is the first one. Is the balancer OK, or is it trashed? I hope your crank isn't broken.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

    Joined:
    Jul 23, 2000
    Posts:
    36,179
    Likes Received:
    1,387
    Location:
    E-town baby!
    It sounds like something is definitely FUBAR with the crank. I would pull the pan off and have a better look. If you chewed the oil seal you probably bent or broke your crank. What were you doing right before all this happened?

    Rene 81 Jimmy,350,SM465/NP205,FF14 bolt,HD Dana 44,3.73's,4"susp.,35"Grabber MT's,body in progress
     
  4. ken

    ken 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,244
    Likes Received:
    0
    Location:
    Anaheim, CA
    Sounds definitely like a broken crank. I've seen many 350 cranks break at the #1 rod journal and create the wobbly harmonic balancer. Sorry!!

    ken
     
  5. Chili 87 K5

    Chili 87 K5 Registered Member

    Joined:
    May 8, 2000
    Posts:
    29
    Likes Received:
    0
    Location:
    CO
    The Balancer has a rut (approx 1.5"L x 3/32"W x 1/32"D) gouged out along the surface that contacts the seal. This is definitely a new "wound", as there is fresh, slightly burred metal all the way around the gash. Looks to me like a bent crankshaft, as the scrape only extends part-way around the balancer shaft; seems like if the shaft were sheared off, I'd have irregular scratches all the way 'round. Also, when I watched the pulleys at idle, there was a definite, regular wobble, as opposed to a stop-start bucking and thrashing.

    Direct answer to your question: I was just driving down a residential street in town, actually slowing to stop at an intersection... I'd feel better if I'd at least been standin' her up under load! However, I've not had this beast but 6 months, and I'm not up to where I'd trust her with my life... yet.

    So, consensus seems to be that my crankshaft is fragged; time for the full rebuild, I guess!

    BTW, thanks to all you mudmeisters for the generous support of newbies like meself!

    Does anybody have a favorite rebuild supplier for crank replacement... maybe pistons, too, eh? Who's good, and why?
     
  6. Blazer1970

    Blazer1970 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,600
    Likes Received:
    0
    Location:
    Old Mission, MI
    Since it sounds like you are going to have to replace your crank, you should look into slapping a GM crate motor in there instead of a rebuild on yours. With the additional cost of a new crank, the pricing will be very competetive with a rebuild of your motor, and you will have a new motor, built with all new parts. Check with Jim Pace for pricing. http://www.paceparts.com


    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  7. truyoopr

    truyoopr Registered Member

    Joined:
    Jul 30, 2000
    Posts:
    17
    Likes Received:
    0
    Location:
    new jersey
    Grate motor is a good idea. But if you are mechanically inclined then i would re build one myself. That way you can put what you wnat into the motor.(flat top pistons,double roller chain,cam, ect). I built my 400 small block for less then $800. And i got some goodies. With the 4.56 gears i can break the 35in swampers with first two gears. A really good source is power house in cali.He knows his stuff. And he can give what you want in a kit. Cheaper then anyone one i found. That is what i would do.

    Come and Get Some
     

Share This Page