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Is my tranny slipping?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by anatomiczero, Feb 23, 2002.

  1. anatomiczero

    anatomiczero 1/2 ton status

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    When I'm at a stop then start to go... I give it some gas and it rolls a little then I feel it thud then it goes, or it will thund a few time then go. I'm going to replace the filter and fluid, is there anything else I can do?

    Some info: Swapped in TH350 about 7 years ago, fluid changed about 5 years ago, when it was installed the mechanic supposedly put in a shift kit (the older tranny shifted better, when it wasn't slipping lol) and a beefed up torque converter for towing.


    <edit> some more info and another q: I have 32* 11.5 BFG AT on it with what I'm guessing 3.08 gears, if I put 3.73 gears in it would it have better acceleration and would the rpm's at freeway speed (65-75) be ok?
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    80' GMC Jimmy 4x4, 350-TH350-NP205<P ID="edit"><FONT class="small">Edited by anatomiczero on 02/23/02 12:21 PM.</FONT></P>
     
  2. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Did you check the fluid level while hot and in park?... sometimes a low fluid level will case it to slip.

    Changed the fluid 5 years ago!?
    I'd say change it more often than that! Once a year... depending on how often you drive your blazer...

    Sounds like a fluid and filter change could help...
    But once it starts slipping really bad, its usually a sign that those clutches are getting burnt down to nothing and are failing to grab now... just slipping... only gets worse and worse if that is the case. Hopefully not.

    Drop the pan and see how much black or silvery crap is in the bottom of the pan.
    ... but then again i didn't have a whole lot of black in the bottom of my tranny pan and the clutches were toast.
    In my TH-400... I took off from a stop sign down the street from my house and "BANG!!!!!" sounded like the rearend let loose or i broke an axle or something... then I realized i had no 3rd gear... and 2nd started slipping until it was gone too... as well as reverse was out....
    Lucky i was close to home cause i wouldn't have gone super far in 1st gear or it would have taken me quite a while!
    my 2 cents.

    [Real Men Don't Care About Gas Mileage Or Rapid Tire Wear!]<a target="_blank" href=http://coloradok5.com/gallery/albuo19>
    MY 1972 K/5</a>
    RyanB.
     
  3. anatomiczero

    anatomiczero 1/2 ton status

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    OK, thanks. It was my dad's I told him a while ago we should drop the pan, he kept saying no it's ok lol. I'll drop it tomorrow maybe or next weekend.

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    80' GMC Jimmy 4x4, 350-TH350-NP205
     
  4. anatomiczero

    anatomiczero 1/2 ton status

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    I dropped the pan today, the fluid was black and at the bottom of the pan it was sludge, very very fine metal shavings mixed with the fluid, it was a silver paste. The whole pan was lined with it about 1/16" inch or more. After I put the new fluid in i thought it was full so i drove it to test it but slipped big time. So I checked it again and it was low so I filled it again, did that a couple of time until it was all through the tranny and now it shifts fine.
     
  5. ducati-cooter

    ducati-cooter Registered Member

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    if you had that much slug in the bottom of the pan and small chunks of metal I would be saving for a rebuild or a new unit. with that much metal and sludge it is only a matter of time.
     
  6. anatomiczero

    anatomiczero 1/2 ton status

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    I was hoping no one would say that lol, this truck is eating me alive! oh well, it's worth it i guess.
     
  7. ducati-cooter

    ducati-cooter Registered Member

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    sorry for the bad news. I know exactly how you feel, I have a 90 jimmy and I have spent close to a grand just doing minor repairs in the last 2 months. the only improvment I have made is adding poly body bushings.
     
  8. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Well, I did a tranny fluid change on my blazer's TH350 this weekend too. I had a little black sludge on the bottom of the pan as well. Some is normal clutch wear, a lot is not good. Metal chunks is where i'd start to get scared.

    A piece of advice, the torque converter holds probally half the total fluid in the tranny it seems like... so when you changed the pan fluid, you were probally only changing about half of the fluid in the tranny. I'll bet if you dropped the pan again now you'd still find some more sludge from what was in the torque converter.
    Wen you eventually do get the tranny rebuilt, if you have it done you can save lots of money dropping it out yourself and just bringing the tranny to a shop to have it rebuilt.
    You'll want to get that converter flushed by a high performance tranny shop it you can find one and if your converter has a drain plug in it... otherwise it would be wise to get a new converter when you rebuild your tranny, so you don't contaminate the new tranny with your old torque converter with burnt sludge fluid.
    And lastly, flush those tranny cooler lines if you do a new transmission. I have a pic of the can of http://communities.msn.com/Ryans1972Blazer/th400transmissionrebuild.msnw?action=ShowPhoto&amp;PhotoID=342
    coolant line flush, you just hook it onto one of the tranny lines and http://communities.msn.com/Ryans1972Blazer/th400transmissionrebuild.msnw?action=ShowPhoto&amp;PhotoID=343
    it flushes out the radiator and the lines for the tranny.

    my 2 cents for ya.
     
  9. anatomiczero

    anatomiczero 1/2 ton status

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    Thanks for the great advice. I might just get a new performance tranny, torque converter and tranny radiator in about 2 years. When my dad first bought it, it hauled ass on the freeway when he floored it. When it shifted from 2nd to 3rd it kicked you in the pants a little. Then when the tranny was rebuilt they put a "beefed up" torque converter in for towing and it's been slugish on shifts. it's always had metal shavings in it, 5 years ago when the engine was put in the mechanic found shavings in the pan. I'll just be saving my pennies..
     

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