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new k5 owner needs transmission help!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kitn0, Aug 13, 2001.

  1. kitn0

    kitn0 Newbie

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    ok guys, glad to find this site, as i am looking to restore my faith in my chevy. i have had this truck for two weeks, and the tranny quit on saturday. i was driving along at ~55, when the rpms when way up, and the truck began to coast. it has no gears at all now, no reverse, no drive, no lows.

    it is an 84 blazer with 350 and 700r4, np208 tcase.

    i pulled the pan and filter. nothing, basically clean fluid, not burned. the shops around want my to tow it in, but i was wondering if anyone has any ideas for stuff i can try first.

    oh, what parts are required to install a th400 in this thing instead :)

    allan
     
  2. newyorkin

    newyorkin 1 ton status

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    That sounds pretty wierd, that it just went on you like that, and now you have no gear whatsoever. I wonder if it's possible that you hit a bump, it knocked into nuetral (maybe loose/weak tranny mount), then the shifter linkage popped out. Does it go into and come out of park? I.E. will it roll if you move the shifter out of park, and hold if you shift into park?

    Take a look at the throttle linkage at the carb, too, and see if there's a cable on the bottom half of the shaft lever (throttle open, cable pulled out in opposite travel to accelerator pedal cable). Make sure there's a cable connected there, and not a broken off end with an empty tube where a cable should be. That's the Throttle Valve cable to the tranny, but even with it broken, you should be able to go into some gear.

    How did the filter look? Maybe that's clogged up real good, blocking flow?? Maybe a cooling line kinked somehow?
    Could just be that the tranny is toast, but I'd try to check it out before throwing in the towel on it. Any history of slippage in it, etc?

    To put in the TH400, I'm pretty sure you'd have to change the output shaft to fit that transfer case, and get a different adapter...

    Good luck, welcome to the best K5 resource on earth, and check this post often in the next few hours!!

    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **Ever stop to think... Then forget to start again?**
     
  3. ftn96

    ftn96 1/2 ton status

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    Im not real familiar with the older 700's. Do these dogs have a a vacum line anywhere on them? Maybe it came off or dry rotted.

    Does anyone have a grinding disk I can borrow?[​IMG]3/4 in progress[​IMG]
    <a target="_blank" href=http://www.nashvillek5.freeservers.com>www.nashvillek5.freeservers.com</a>
     
  4. 4x4blazer

    4x4blazer 1/2 ton status

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    I was in your shoes a few years back. I have a '84 with 350, used to have 700r4, and np208. I kept toasting the 700s so I finally put a th400 in its place. The early 700r4s are weak. Either put a newer 700 in it or go for the th400. For the swap to the 400 you will need a new tail shaft, a dipstick for a th400, and an adapter kit. I got my kit from Transadapters.
    You will have to modify your crossmember too.
     
  5. rampage

    rampage 1/2 ton status

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    That same thing happened to my 700R4 just after it was rebuilt. Basically my torque converter grenaded. Guy at the tranny shop said it was a defective torque converter. I take it you just bought it 2 weeks ago ... maybe this is why it was up for sale.
     
  6. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    Sounds to me like the chain in your t-case might have let go. Shift it in to 4-lo and lock the hubs and see if you have gears then. This happened to me a few years back and I thought it was the trans. This is a quick way to eliminate the t-case as the problem. Good luck!

    '85 K5 : Run it til it breaks, then fix it and go again!
     
  7. Blazer1970

    Blazer1970 1/2 ton status

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    I agree with Rampage, most likely the torque converter self destructed. The early lockup torque converters were not real good.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  8. kitn0

    kitn0 Newbie

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    well, did not get a chance to look at it last night (i was working on my kitchen remodeling project) but there is absolutely nothing in the pan, and the filter looked good, and was a nice tight fit on its outlet side into the tranny. the tv cable is there, and is not bound up or anything, and i dont think the th700 has any vacuum modulation line to break.

    and, it is not just a bump causing the neutral gear, i have messed with the manual linkage at the tranny end, and it is most definately moving between gears. park works as well, so the tcase is fine too. (too bad, i have a spare tcase from a jeep with the bolt-on yoke i would like to install)

    so i am thinking the overrun sprag in the torque converter, or the front pump is toast. most likely the former, since the later would probably leave some foo in the pan.

    here is something else odd- when i put the tcase in N, the tranny is spinning, cause i cant put it in park (grinding noise) but if i leave the tcase in any gear, the tranny seems to be slipping in all gears.

    ok, so back to the 400, a guy i work with has a suburban, with the np208 and th400 behind a 350. but the tcase seems much further rearward in his chassis. how does the th400/adapter compair in length to the 700/adapter?

    allan

    <P ID="edit"><FONT class="small">Edited by kitn0 on 08/14/01 09:13 AM.</FONT></P>
     
  9. Blazer1970

    Blazer1970 1/2 ton status

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    If those lockup converters go bad, you can usually make the truck creep (forward or reverse) by revving the engine a little, so it wouldn't surprise me that it will spin the t-case input.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     

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