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TH350 Transmission Leak

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by RiceDaddy, Feb 23, 2003.

  1. RiceDaddy

    RiceDaddy Registered Member

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    Fellas,

    I've got a question that basically boils down to my lack of knowledge of my tranny. I've got the TH350 tranny on a pretty much stock 1980 K5 with the 350 engine and the NP205 t-case. I changed the ATF a couple thousand miles ago and I check it regularly. I checked it again Friday and it looked and smelled good and the fluid was at the correct level. Saturday morning, I drove the blazer about 60 miles at roughly 70-85 mph. A few hills in there, but no downshifting. When I got to my destination, there was ATF all over the bottom of my truck. I had lost around 1-2 quarts of fluid and now the fluid was brownish and didn't smell good. I can't tell if the leak is from the front seal, the pan, or the dipstick o-ring. It doesn't look like I puked any out the top of the dipstick. The truck sat for 8 hours and I added fluid back to the correct level. I drove it home (60 miles) back and checked the fluid several times on the way back. I drove another 20 miles today and I have not lost any more fluid since the first trip.

    What's a plausible explanation for my leak and why isn't it leaking any more? I think it might be coming from the dipstick o-ring area, but why isn't it leaking now? I need help /forums/images/graemlins/crazy.gif
     
  2. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Look and see if yout dipstick has worked its way loose a little bit.
    Well now you get to wipe everything down really good underneath your truck. Just keep driving it and when you park it get out and get under your truck. If you keep everything pretty clean it should be easy to determine where it's leaking from.

    ...And carry a fire extinguisher with you!
    I've had my tranny puke fluid and catch on fire. /forums/images/graemlins/angryfire.gif Not fun. /forums/images/graemlins/k5.gif
     
  3. Triaged

    Triaged 1/2 ton status

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    I'll second the fire ext.!

    If you don't have a aux. tranny cooler get one now. You also need to change the fluid again if it smells burnt.

    Then clean off the bottom of the truck so you can tell where it is coming from. It might have to be in gear and have a load on it for you to see the leak...but a 2qt. leak in 60mi. should be easy to spot.
     
  4. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Yeah, Dan it's got to be the curse of Hollister!
    First you catch your tranny fluid on fire, then the next trip its Zakk's dash, the following trip its my tranny fluid on fire. /forums/images/graemlins/angryfire.gif /forums/images/graemlins/eek.gif
    We're going to hollister again this coming weekend... wish us luck! /forums/images/graemlins/rotfl.gif /forums/images/graemlins/k5.gif
     
  5. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Could be coming from dipstick tube, kick-down cable, cooler line fitting, pan gasket, front pump seal, etc. Clean it down and watch it. The fact that it is darker and not smelling too good, probably means it's time (or will be soon) for a rebuild. How many miles on this thing? Auto trannies are not designed to last forever. Clutch, bands, and steels wear out. It might even be worth it to bring it to a tranny shop (NOT AAMCO) and see what they say. As stated, if the fluid heats enough, it can expand and spit out the dipstick tube or many times it will spit out the vent on top of the tranny (hard to see). Mine on the 78 spewed out the dipstick tube about a month back and started on fire when it hit the header pipe. Fire extinquishers are your friend.... /forums/images/graemlins/thumb.gif Tranny needed a rebuild as the P.O. did a hackjob on it.
     
  6. RiceDaddy

    RiceDaddy Registered Member

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    Thankfully I've got a fire extinguisher on board. Didn't have to use it this time. I'm going to change the fluid and wipe it down real good then check for leakage. When I looked at it the first time fluid looked like it might be coming from the top of the tranny. The cooler fittings looked dry. Is there a vent on top? I couldn't find it if there is.

    I'm not the original owner of the blazer, but I have documentation that the tranny was rebuilt 30000 miles ago. Total mileage on the truck is 80000. I know this seems low, but I bought it from a wealthy woman who got it in a divorce. The couple used it as their "SUV" at their ski cabin in Angel Fire. It basically just stayed parked there year-round and they used it whenever they were at the cabin; which wasn't very often.
     
  7. Triaged

    Triaged 1/2 ton status

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    There is a vent on the top. It is on the driver's side twards the front and almost at the top. You will get dirty fealing around for it!
     
  8. RiceDaddy

    RiceDaddy Registered Member

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    In a continuing effort to appear stupid, is this the vent your talking about?

    [​IMG]
     
  9. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    In a continuing effort to appear stupid, is this the vent your talking about?

    [​IMG]

    [/ QUOTE ]

    Yep that's the one.
    /forums/images/graemlins/thumb.gif
     
  10. RiceDaddy

    RiceDaddy Registered Member

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    Thanks

    It looks like the fluid I lost came from that vent. Most likely as a result of overheating. I'm going to change the fluid and wipe everything down good and continue to check for a reoccurring leak. It's probably inevitable that I'll be rebuilding it soon. Thanks to everyone for their help.
     

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