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Help!! Rear Main Seal Problems!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by trouble1, Oct 6, 2002.

  1. trouble1

    trouble1 1/2 ton status

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    I'm going thru Rear main seals quicker than I go thru a tank of gas....and I'm serious. Never had a problem till about three weeks ago when the first one went. Replaced it, never really thought anything about it...just thought age caught up with it. 200 miles later, its leaking again. I replaced the breather and pcv vale, then replace the seal again. Saturday it blew again. I really dont want to keep dropping my tranny everytime I get Gas!!! Any ideas would be greatly appreciated. Oh yea...305 chevy, 700R4, several mods to the motor....but that was a long time ago. /forums/images/graemlins/angryfire.gif
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Blowing blowing (like blown out, all at one time) or does it just start leaking a lot?

    Friends 350 started leaking quarts of oil at a time through the main seal (bought used, so no idea if it was a continuation of a problem) and he ended up getting an "oversized" rear main seal for it apparently. Never heard of such a thing before, but next race, he didn't leak any oil.
     
  3. HarryH3

    HarryH3 1 ton status Author

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    Also be sure that you lube the edge of the seal that goes against the crankshaft so that it doesn't get a friction burn when you first start the engine after replacing the seal.
     
  4. Z3PR

    Z3PR Banned

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    That sucks !!! I hate fixing something (Going through all that work) to just have too keep redoing it over n over.
    Might wanta consitter upgrading to a larger engine like a 383 stroker. Start freash, 305 is okay in a pavement princess, but lacking for everything else. I have no idea what would couse it to keep tearing out the rear main seal. IF , and that's a big IF, you have to sink some high dollors in it for repair, I'd seriously consitter a different motor.
     
  5. trouble1

    trouble1 1/2 ton status

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    totally agree with ya!!!!I've been saving my pennys, the truck deserves a good motor...What I really want is a BUILT 454, but cant afford it yet, so in the mean time...I got to figure this out!!! /forums/images/graemlins/confused.gif
     
  6. Panther

    Panther 1/2 ton status

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    You might want to make sure it's not the oil pan gasket. It sounds like you've had the pan on and off a few times.
     
  7. CooknwithGas

    CooknwithGas 1/2 ton status

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    Did you inspect the crankshaft where the seal goes? I have seen the seal eat right into the steel crankshaft and cause a groove there. I think there is a cure for this - a different seal, double seal, or something like that, but the groove cut in the cranshaft will cause the problem you are talking about. I had the same problem on the front seal and they make a sleeve for the front. I'm not sure about the rear.
     
  8. Stoopalini

    Stoopalini 1/2 ton status

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    I had a very similar thing happen with my rear main a while back. If you search by my username, you'll find many a post on it.

    I replaced 4 rear mains within 1000 miles! It was so aggrivating. It turns out that my mechanical fuel pump was bad and was allowing gas to seep into the oil. This thinned the oil out enough to cause it to leak through the rear main within 100 - 200 miles.

    A new fuel pump fixed my issue. It's been about 6 months or so, and it's still dry underneath /forums/images/graemlins/smile.gif

    Good luck,
    Thomas.
     
  9. trouble1

    trouble1 1/2 ton status

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    I Had IT!!!!!!!!! Thanks for all your suggestions....but I'm gonna throw this @&%^* 305 away...I've put enough money in this thing to sink the freaking titanic! Which leads to my next post, Again....thanx for all the suggestions. By the way...if you want a well built 305, I know a dumpster that one is about to sit in. /forums/images/graemlins/angryfire.gif
     

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