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np203 and rear end noise help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by vegas76k5, Dec 25, 2003.

  1. vegas76k5

    vegas76k5 Registered Member

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    I have a problem and don't know where to start. It first started with a rattle/rumble that seemed to come from the 203. It got louder and increased in speed with the truck's speed when I was on the gas. No noise at same speed when I let off the gas. I babied it for about a week, but got on the gas hard a few times the other day. Now I have the same noise from the 203, and also a clunk from the rear end area with almost every tire revolution. Also, I get clunking/rattling when I coast now.

    Some information that may help. 1976 Blazer didn't run when I got it, so I don't know about any noises. Installed rebuilt 350 and new TH350. Drove 2 weeks, no unexpected noises. Whirling sound from 12 bolt rear area. Pulled cover, found a crack in it and very little gear oil inside. No metal fragments or shavings. Cleaned, installed new cover, filled with gear oil. Next time I went on the freway is when I heard the noise from the 203.

    The 203 is not converted and there is no front drive shaft.

    Sorry if this is long, but I wanted to give all the details I could think of. Any ideas on where to start is appreciated.
     
  2. K5DRAGER

    K5DRAGER 1/2 ton status

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    Just a guess but check the fluid level in the 203, and the transmision, then check the rear u-joints. If they check out alright then pull the cover on the rear end again. Good luck
     
  3. vegas76k5

    vegas76k5 Registered Member

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    Fluid level of the 203 and TH350 are both good. How do I check the u-joints?
     
  4. R72K5

    R72K5 Banned

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    U joints check for slop, grab hold of driveline and try to laterally movee the shaft sideways anmd up and down and see if any slop at U joint or not, you are looking for slop wear in the joints, should be none if are in good shape,. buit wont tell you if they are dry though

    most all of the U joints are sealed ungreasable ones from factory like on my 83 k20, spicer outside clips style*
     

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