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Rear seal leak ...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Innerpiece, Mar 14, 2001.

  1. Innerpiece

    Innerpiece 1/2 ton status

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    well -- I've pinpointed my oil leak to the rear seal (worst possibility of course) and I think I may need some help.

    Info -- 87 silverado blazer. 305 TBI, 400 tranny (i think .. I'll check), np 208, 32" tires, no lift.

    Haynes says that starting in 87 they used a one piece rear seal and that in order to change it you have to unhook the tranny and partially lift the engine. is this correct? anyone have any experience w/ this? Is it particularly hard to do yourself (I have access to a good shop, but limited intelligent help as I'm stationed in Missississississississpipiipppi)?

    How much should expect to pay if I drop it off at a shop?

    I'm only leaking about a pint every 200 Miles ... but it's enough to mark up the driveway and coat the underside (no rust tho!) ... not a huge problem but I'm kinda anal. I also hate wasting time, and If I'm going to halfway pull the engine to do the rear seal, I might as well all-the-way pull the engine, rebuild and bore it, rebuild the tranny, etc. while im at it (low funds tho)..

    Any help would be appreciated.
     
  2. CaptCrunch

    CaptCrunch 1/2 ton status

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    The official word here is SOL. You either have to A) pull out the motor... or B) remove the trans and t-case from the truck, pull down the oil pan and remove the crank... so might as well do bearings too). I'd say just leave it and do all the engine stuff during a rebuild

    1987 Chevy K5 Blazer- 350 TBI
     
  3. HarryH3

    HarryH3 1 ton status Author

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    I don't think you have to mess with the oil pan or the crankshaft to change the seal on an engine with the one piece seal. Once you get to the seal area, just onbolt the aluminum housing that the seal fits into, take it over to the workbench and swap the seal, then put everything back together.

    The rear main seal on those engines looks like a huge wheel bearing seal. It's just pressed into the aluminum housing that bolts to the back of the block.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  4. Innerpiece

    Innerpiece 1/2 ton status

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    Yes = but won't I either have to take the engine or the tranny out to get at the seal area?
     
  5. Innerpiece

    Innerpiece 1/2 ton status

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    ARRGGGHHH

    Well -- My oil leak is getting worse ...

    I've been doing a little road tripping in the blazer to get some highway miles on it and see if some things settle out. At highway speeds, the damn thing is leaking like a sieve. I'm loosing a quart every fill-up (300 miles). It's leaking from the rear seal onto the torque converter and getting slung all over everwhere. The best part is, the wind blows it back down the drivetrain to the rear wheels (drum brakes don't like oil). Then when I stop, the quart of oil stuck on the undercarriage rains down and leaves a nice slick. So I need help. I need to minimize the pain until I have the time and money to fix it right.

    (1) Seal conditioners. Does anyone out there know of any good seal conditioners that may help.

    (2) Oil. I'm using penzoil 10W30. Would a thicker oil slow the leak? Pro's con's? Recommendations?

    On the plus side, I'm getting a complete 5 quart oil change every 2 months or so (faster If I road trip). All I have to do is change the filter every 3000 miles (insert sarcasm here)
     
  6. HarryH3

    HarryH3 1 ton status Author

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    Yes, you still have to move the tranny out of the way to get to the seal. Once that's done, there are just a few bolts to remove the seal and housing. Replacing the one-piece seal is easy. Getting to it is not. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  7. Innerpiece

    Innerpiece 1/2 ton status

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    so what can I do in the mean time to slow the leak?
     
  8. Innerpiece

    Innerpiece 1/2 ton status

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    what weight motor oil would you recommend to slow the leak? (pros/cons) what about oil additives that claim to be seal conditioners?
     
  9. HarryH3

    HarryH3 1 ton status Author

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    I don't know if any of those "miracle in a bottle" seal conditioners work very well. Heavier oil may slow the leak marginally, but you'll probably just have to bite the bullet and get in there and change the seal. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  10. 87K54WD

    87K54WD 1/2 ton status

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    Hey Harry .... I saw your earlier post about how to change the seal out. Would this be the same for a manual tranny? I've got an 87 too and I was changing my oil last night and noticed what appears to be the rear oil seal half way out. There was not any FRESH oil but I could see a pattern where in the past it had been leaking there. To me, it looked real easy to fix. Just looked like I had to unbolt the cover between the oil pan and fly wheel/clutch assembly and pull down. Put in a new seal and bolt back up. It didn't look like I had to move the tranny or lift the engine. Any ideas or suggestions. Thanks!
     
  11. blazbrnc

    blazbrnc 1/2 ton status

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    You may want to keep in mind that rear main seals usually go bad when they are subjected to deep water crossings. The sandy, dirty water gets in the groove and causes the leak. What it also causes is a nice groove worn into your crank tailshaft. Therefore you can replace the seal and it will probably not leak for a while. But once that rough groove in the crank starts eating your seal, you get another leak. Your leakage sound excessive, so I would change the seal, but don't be surprised if it comes back.
     
  12. HarryH3

    HarryH3 1 ton status Author

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    The flywheel has to be unbolted from the crank first, so you have to get the trans out of the way. [​IMG] The one-piece rear main seal slips over the end of the crankshaft, so there's no way to "pull down" on it to replace it. It's a $7 seal that takes $200 of labor to get to. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     

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