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Front/rear seal?

Discussion in 'The Garage' started by Chevy305, Jan 13, 2007.

  1. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    I think the front and rear seals are leaking on my 83 305. The front one has always had a very slow leak, but now the rear is suddenly dripping a few drops. I want to get it fixed before it ruins my driveway.

    I've never changed seals before so, what needs to be done, and what gaskets/seals do I need?
     
  2. 454k30

    454k30 1/2 ton status GMOTM Winner

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    Im not sure if the 305 has a two piece rear main seal or not but someone here will. The front seal is kinda a pain because you have to pull off everything in front of the timing chain cover this includes the harmonic balancer. Take off the chain cover itself and then change out the seal. The rear main (if its a 2 piece) requires the oil pan and rear main cap to be removed. I believe that a single piece rear main requires the tranny to come off.
     
  3. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Since its a 83 I think it should be a 2 piece rear seal.

    Is there any thing else I should do to my engine while I have the oil pan off?

    Also is there a particular brand of gaskets/seals that anyone would prefer?
     
  4. broncoman6524

    broncoman6524 1/2 ton status

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    this may sound stupid...but check your valve covers....mine were leaking and did just this. it would appear that my rear main was leaking and nautrally pissed me off. lol
     
  5. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    I double checked and its definately from the rear main. The front might just be from timing cover gasket, but either way it would be good to replace both for good measure.
     
  6. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    So a little irony...

    Ok so I ordered all new gaskets and seals and harware to do the new rear seal, and now its not really leaking anymore. There still is a very slight drip but much slower than before. :rolleyes:

    But since I have everything I already need, when I have the oil pan off, is there anything that i should check while i'm in there?


    Here pics of what i bought:

    rear seal stuff 3.jpg

    rear seal stuff 1.jpg

    rear seal stuff 2.jpg

    rear seal stuff 3.jpg

    rear seal stuff 1.jpg

    rear seal stuff 2.jpg
     
  7. 1977k5

    1977k5 3/4 ton status Vendor

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    If you want, you can pull the main bearing caps and/or the rod bearing caps to see what shape they are in.

    I would leave it if the oil pressure is good and replace the seals :D
     
  8. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    oil pressure is decent at about 20psi at idle.
     
  9. diesel4me

    diesel4me 1 ton status Premium Member

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    might wanna check the oil pump,timing chain.....

    When I pulled the 305 I put in my 79 C10 out of the '86 van it came in,the oil pan was rotted thru and leaking..so I had to buy a new one..

    After I got the oil pan off,I noticed the cam gears nylon teeth were in the sludge at the bottom of the pan,and the oil pump screen had several lodged in it as well..pulling the oil pump cover off revealed one made it into the gears..:doah: ---engine had excellent oil pressure,I was suprised to see that..but I didn't like the way the oil pump felt while turning it by hand,so for 12.99 at Auto-Zone I got a brand new stock Melling pump,and for another 5 bucks I bought the metal "coupling sleeve" to replace the cheesy plastic one on the pumps driveshaft..also put a 3 peice timing gear setup (with a metal gear for the cam this time!) in it for another 19.99!..

    I learned they sell "value-craft" one peice oil pan gaskets (made by Fel-Pro,same exact gasket as the "Fel-Pro" one,even had the same numbers molded into it,for 18.99--the Fel Pro one was 36 bucks,more than I paid for the oil pan!..:eek1: )..so I opted for a new gasket,even though the old one survived and I probably could have re-used it..

    I'd make sure the oil pump and timing chain are in good shape before replacing the oil pan..it only cost me 60 bucks for the oil pump,new screen,timing gear/chain setup,new oil pump drive sleeve,oil pan gasket..its a good idea to scrap any oil pump with over 100K on it,regardless if it still works ok..might as well do it while your in there..

    Also,I've seen oil pressure sending units leak, and mimic rear main seal leaks..or the rear of the intake right behind there,that can leak too, and appear to be the rear main..and if you have blowby or a clogged PCV system,pressure can build up in the crankcase and make even perfect seals leak too...:crazy:
     
  10. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Well, I have no idea how many miles are on the engine, but I know all the internals should be original. When I do finally do it I'll make sure to check the oil pump and timing chain.
     

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