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TH350 WATER PROOF GOOF, VENT INFO

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by elkboy, Jul 18, 2001.

  1. elkboy

    elkboy 1/2 ton status

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    I recently put a TH350 in my K5 in place of the 700R4. I used a pre 1980 case and put in a newer GM dipstick that is water proof. DOOOH, the pre 80 4x4 cases are vented through the dipstick tube, after filling my t-case halfway up with tranney fluid, I finally figured it out. When things get hot and expand the pressure has to go somewhere, in this case it was the input seal in the t-case that was the path of least resistance. To solve the problem I drilled and tapped the dipstick tube and put in a small hose fitting and a hose that runs into the cab for venting. Now it's water tight and no more tranny fluid in the t-case. Just wanted to share in case any body else gets the water proof bug.

    <font color=red> Elkboy </font color=red> 82 K5 fuel injected H.O.305, TH350/205, 14bolt/10bolt and 39.5 TSL's.
     
  2. POWERMAD

    POWERMAD 1/2 ton status

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    Hey Norm
    That's a pretty good idea.
    Are ya wheeling that bad boy yet?


    my truck's not dirty, it's earth tone paint
     
  3. Executioner

    Executioner 1/2 ton status

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    the pre 80 4x4 cases are vented through the dipstick tube,

    Are you sure ? Seams to me I have seen many th350 from 73-79, in Blazers with the vent
    on top of the tranny, kinda near the pump area !
    If you sure please provide a verifiable source.
    Good luck
     
  4. Thunder

    Thunder 3/4 ton status

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    Hmmm.... I never heard of that either
    Every one I have seen vents from the top too. I dont think the dip stick tube is a very efficent way to vent a tranny. Any build up of pressure would blow tranny fluid out the tube.

    <font color=orange> You are just jealous, because the voices only talk to me.</font color=orange>
     
  5. elkboy

    elkboy 1/2 ton status

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    Ya, I took it out on Saturday and made the dustbowl run in TSF. When I get it locked and my winch mounts on, it will be time to make a serious run (after a little rain to keep the dust down).

    <font color=red> Elkboy </font color=red> 82 K5 fuel injected H.O.305, TH350/205, 14bolt/10bolt and 39.5 TSL's.
     
  6. elkboy

    elkboy 1/2 ton status

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    This is a unscientific observation I made on my TH350 and a couple of TH350's in a junkyard. The two pre 80 4x4 TH350 cases I have seen had no vents on the case that I could see. I saw a couple of TH350's and a TH400 out of a 2wheel drive that had vents. I'm not claiming to be an expert, but if someoine out there is a tranny expert, feel free to comment. Also, venting means allowing the air pressure to equalize between the inside and outside ot the tranny, if there is fluid involved, you have problems. So from an engineering perspective, why not use the dipstick tube for venting? Not trying to get into a who's right war, but it is an interesting question.

    <font color=red> Elkboy </font color=red> 82 K5 fuel injected H.O.305, TH350/205, 14bolt/10bolt and 39.5 TSL's.
     
  7. Executioner

    Executioner 1/2 ton status

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    Opps I must have misread your post, I missed the words of opinion !
    You need to become a tranny expert
     
  8. Twiz

    Twiz 1/2 ton status

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    Just checked 3 of the 5 T350s I have here. They have a vent on the top left (drivers side) by the bell houseing. Not tapped and no hose or nipple- just a hole.

    Still a good idea Elkboy. Here's another point of view on the locking dip stick thing.
    IN MY OPINION!
    The bottom of the dip stick tube may be soaking in ATF. So, if the trans does get hot enuff, it could blow some trans fluid up the tube, and on to the hot exhaust and may cause an engine fire. Not likely- but it could happen. So doing what Elkboy did sounds to me like a solid idea. At one time G.M. had a recall on dip sticks for that very same resson (possible engine fires), exchange non-locking dip-stick to a locking dip-stick. If I remember right they where 4L60s in the old body style S10 Blazers.

    Twiztid
     
  9. Triaged

    Triaged 1/2 ton status

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    Not likely....Happened to mine this weekend. Luckily the fire did no damage because of a few quick thinkers with extinguishers.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
     
  10. ratchetmaster

    ratchetmaster Registered Member

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    As was well stated above,
    The venting is just to equalize the pressure.

    It can not use the dip stick tube effectively as a vent because the tube is submerged into the fluid . . . therefore if some "pressure" builds it would push the fluid up the tube and possibly leak fluid out (although the tube is pretty long so it might work ok).
    All dip sticks I have seen have a rubber gromit (sp) at the top to prevent this from happening.

    All rwd cars I have seen have vent tubes on the top side of the trans.
     
  11. limey

    limey 1/2 ton status

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    my 74 jimmy has the vent on the top driver side near the bell housing i taped a pice of tubing in to it and put some hose on it and ran it up near the break booster
     
  12. wrathORC

    wrathORC 1/2 ton status

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    I think it was the 88-93 700R4 and 4L60[e] transmissions. There was a TSB on it. My Dad's 89 pickup had this problem. We were on the expressway and we noticed some haze in the distance in the mirrors. We pulled off at a rest stop and when we got down to 35mph there was a lot of smoke. We both jumped out, he opened the hood, and we both threw our glasses of iced-tea on the passenger manifold because as soon as the ATF hit the manifold it was igniting. The transmission had actually overheated and was just squirting ATF out the tube.

    As a side note, I have 2 TH350s laying on the ground and they both have vent tubes pointing towards the back on the top of the transmission. One is plastic and one is aluminum. The 700R4 in my truck has an aluminum one as well.
     
  13. Calclips

    Calclips 1/2 ton status

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    Tranny fluid catches vehicles on fire quite a bit, a friend of mine lost his plow truck that way. Blew one of the cooler lines on it and that was all she wrote..
     
  14. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    Tranny fluid catches vehicles on fire quite a bit, a friend of mine lost his plow truck that way. Blew one of the cooler lines on it and that was all she wrote..

    [/ QUOTE ]
    Word.
    I had it happen to me at hollister. /forums/images/graemlins/angryfire.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/frown.gif Tranny puked some fluid and next thing i know my truck is dripping fire! /forums/images/graemlins/eek.gif
    It's the curse of hollister, almost every trip someone catches on fire. /forums/images/graemlins/shocked.gif /forums/images/graemlins/rotfl.gif First Triaged, then Zakk, then Me... Who's next. /forums/images/graemlins/confused.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/rotfl.gif
     
  15. twenty_below0

    twenty_below0 1/2 ton status

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    So where does the fluid most commonly come from , the top little vent or the tube , and if the tube out the top or out around where it goes in the tranny (at the bottom) I have a newer stile filling tube with the click over locking red top . So if this doesn't solve the issue how do we alleviate the possiblilty of the fire issue ? /forums/images/graemlins/confused.gif
     

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