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To power flush a 700R4 or not

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Alex, Jul 30, 2001.

  1. Alex

    Alex Registered Member

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    Hello all, is it a good idea to power flush a tranny? I've heard mix feeling about doing it because of the chemical reside that remains in the tranny. I have a 700R4 in a '91.
    Alex
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    700's are very touchy trannys i would do it as a preventitive thing but if the fluid is really bad then i would do it for sure

    77blazer see it at<a target="_blank" href=http://community.webshots.com/user/ssmith6333>http://community.webshots.com/user/ssmith6333</a>
     
  3. solowookie

    solowookie 1/2 ton status

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    when I changed the filter in my tranny the fluid that came out was really burnt so I had it flushed. thats what everybody recommended with bad fluid.

    [​IMG] <font color=blue> Jeff </font color=blue> [​IMG]
     
  4. Rockjunkies

    Rockjunkies 1/2 ton status

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    I may be wrong, but I believe that they use Tranny fluid to flush the tranny. So I cannot see how it could leave a chemical risidue. Unless they are adding a chemical cleaner to the fluid. I have had transmision shops tell me that they backflush the system, so that there is no need to change the filter because it pushes all the trash out of it. I would never allow that because that could also cycle the trash through the entire system. And that could surely mean early transmision failure.

    Keep it simple!
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Back flushing just pushes the fluid in from the cooler lines. it's not going to push stuff back into the workings of the tranny It would drop into the pan. I still would drop the pan. Back fushing might blow out the filter element and you would never know it without dropping the pan. Then you would be running unfilered and really do in the tranny.
    Now here is another thing you need to be aware of. If this tranny has high miles and never been serviced the new fluid may be the straw the breaks the camels back. The new fluid is going to have more slip. The old fluid has very fine particals of clutch and metal floating around in it. It's so fine that it will pass through most tranny filters unless your running a Screw on filter Like a Oil filter. This fine desbris may be all that's keeping that tranny going. It may well fail shortly after servicing. You need to uderstand that is a risk your running and most places that service trannys will tell you the same. If it fails it not the shop that services it's fault it the lack of maintance durring the life of the tranny that cause it to fail.

    It's not my damn planet monkey boy!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>

    Grim-Reaper
     
  6. Derf00

    Derf00 1/2 ton status

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    According to all the 700R4 "experts" I have talked to, Grimm is 100% correct. If you don't have good records on your transmission fluid changes, leave it alone, just keep it full. It might be interesting to have a poll to see how many 700's failed after being serviced.

    Derf00

    "A WISE MONKEY NEVER MONKEYS WITH ANOTHER MONKEY'S MONKEY."
     
  7. Rockjunkies

    Rockjunkies 1/2 ton status

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    If back flushing just cleans out the lines and not the entire system, than why would there be a concern of it tearing the filter? It would have to pass thru the valve body to get to the filter. And there is alot of fine moving parts in the valve body alone. I was simply stating that it would be a good idea to replace the filter no matter what type of service it recieves.

    Keep it simple!
     
  8. 86K5inMN

    86K5inMN Registered Member

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    We have a family friend thats been in the tranny business for at least 25 years. He won't do anything to a 700r4 that hasn't been regularly maintained other than replace it. I love these trannies but I too happen to have one in need of replacement. When built and maintained properly these are great trannies.
     
  9. Alex

    Alex Registered Member

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    OK, now I'm a little lost. I just bought the Blazer, it has 86k original miles and I've always been anal about changing all fluids, but this is the first I've heard about damaging a transmission after servicing. More on the matter would help, any transmission experts out there? Thanks in advance.
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

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    You guys make somewhat of a good point, but I would flush any tranny that still shifts properly. Bad fluid will kill a tranny just as fast. Get it flushed, then drop the pan.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    The pump sucks up the fluid through the filter and sends it to the cooler and then it goes to the valve body for distirbution to the clutches.
    Back flushing would mean pumping backwards through the cooler back through the pump where it would come out the filter. If they are pumping it into the other side then they are just pushing it through the throttle body in the normal dirrection of travel. That would be no different than the pump pushing fresh ATF through the system so it's not back flushing. You also would not be able to suck it back out of the tranny through the valve body because it when it hits a clutch back it's above fluid level. When the clutch is done it with it the fluid gets purged where it drops to the pan. Now if they can flush out the converter that would be nice but that would require the tranny to be running to get the fluid to run to get it to work. That sort of scares me and your still not really going to be able to get the converter cleand out because centrifical force is going to keep any heavy crud slung to the outside.
    I do agree that a new filter is the way to go. I also feel those flush things are point less. You can't clear the torq converter unless it's equipped with a drain plug (and some are). The converter holds the majority of the fluid. Dropping the pan you only change about 3-4 quarts of the 8-9 or so a tranny holds.

    It's not my damn planet monkey boy!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>

    Grim-Reaper
     
  12. Alex

    Alex Registered Member

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    Grim, how can I tell if my 700R4 has a torque converter drain plug? I know on my Bronco you can remove the front cover of the housing and the converter and plug are visible &amp; serviceable.
    Alex
     
  13. 78Blazer

    78Blazer 1/2 ton status

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    Alls I got to say is if it shifts fine now ... Dont do it.... Drop the pan change the filter and gasket and go.. Ive seen many a trannys start to slip after wards including my own that only had 20,000 on it after the rebuild. I used to work at a Quick oil change and they pushed it like crazzy and had lots of trannys coming back slipping. Now if it is done right from the start of being new its not a bad idea..



    Scott
    78blazer
     
  14. Itali83

    Itali83 1/2 ton status

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    so 78, just draining oil, changing filter and pan gasket is no prob?? The new oil wont mess up old seals and stuff?? Just wondering. My 700's oil looks clean and dosen't smell burnt or anything, but I was thinking of doing the filter, but maybe I won't. Just wondering. Thanks
    Ben 87 Jimmy
    <font color=blue>Rust=Bad</font color=blue>
     
  15. K5XLR8R

    K5XLR8R 1/2 ton status

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    JUST PERFECT!!!!!!!! Now I see this post AFTER I've already had the fluid,filter changed...not to mention the fact that the fluid had ALOT of metal shavings in it......what are some symtoms of it going south???
    Thanks!
    Jordan

    Yep!! It's definatly a jEEP thing...So, what your excuse???
     
  16. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I flushed mine, I wouldn't have it any other way. If your fluid is junk your tranny will wear out quickly anyway.

    There's no such thing as "backflushing" to my knowledge. All the machines I've seen hook up to a cooler line, flushing the transmission, lines, cooler, and torque converter, purging 100% of the old fluid with 14 quarts of new.

    I work at a Jiffy Lube and have never seen nor heard of a tranny that wasn't JUNK that was flushed and acted up.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  17. solowookie

    solowookie 1/2 ton status

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    <blockquote><font class="small">In reply to:</font><hr>

    I work at a Jiffy Lube and have never seen nor heard of a tranny that wasn't JUNK that was flushed and acted up.

    <hr></blockquote>

    yea, but I think his point is that even junk can make it a lot further if not flushed. man if you can milk some extra miles out of the thing then why not???

    [​IMG] <font color=blue> Jeff </font color=blue> [​IMG]
     
  18. jarheadk5

    jarheadk5 1/2 ton status

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    Can't speak for anyone else, but the guy I take my truck to for the tranny powerflush has a machine that does it. Hooks up in series with the cooler lines and purges all the old fluid with the engine running, to ensure there's fresh fluid everywhere. Grim's probably right, any heavy stuff in the converter will probably stay there, but at least there's fresh fluid in the rest of the tranny. Then he drops &amp; cleans the pan &amp; changes the filter, tops it back off, and away we go. I had this done last year on my 700R4 (a rebuild with around 20K on it), and it "felt" like it shifted smoother and better. As soon as I have the money, I'll get it done this year too.
    I trust this guy not to screw me over; he and his father have been the "family mechanic" on my stepdad's side for well over 30 years, with very few problems.

    If at first you don't succeed, failure may be your style...
    [​IMG] <font color=green>Semper Maintenance!<font color=black>
     
  19. Twiz

    Twiz 1/2 ton status

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    -I think a dry tarnny will take around 12 qts
    -A standered "trans service" drains about 4 qts (pan and filter)
    -Some Torque converters have drain holes, pull the inspection cover, mark the coverter, and rotate the engine or flex plate useing a socket on the crank pully or a use something on the fly wheel, look for a small bolt or plug on the converter- some do, most don't.
    -I pretty sure converters have filtered fluid in them, so the heavy meterial should be kept to a minimum.
    -As far as I know, correct back flushing is done by discannecting BOTH trans cooler lines and flushing out the cooler and lines only -not the trans. Generaly done when a new transmision is installed (highly recomended- back flushing, that is)
    -As far as I know, a proper trans power flush. Does not include a "solvent" of any kind. Also, one cooler line is removed from the radiator and fresh fluid is used to "push" the old fluid out with the engine running.
    -Sometimes, new fluids can quicken the demise of and engine or trans. Only when the proper matinecne and fluid changes have not been followed. But, to put some minds to rest here, if the trans was good going in, it should be better comeing out.

    -Use DextronIII

    Twiztid
     
  20. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I absolutely agree. If your trans is in good condition, flush it. If it's slipping already, leave it alone.

    We do three services at Jiffy lube:

    TS1 = Pan drop, filter and gasket, about 4-5 qts.
    TS4 = Flush
    TS5 = Pan drop and flush

    I would recommend that all of you get your transmissions at least flushed by someone with a machine, then drop the pan and change the filter to get all the debris out that you just flushed through the filter. If you want do, drop the pan, take a look and if it's not that bad, you've got nothing to worry about, flush it. If it's got a lot of crap in the bottom of it, leave it alone and put some new fluid in it.

    Crappy trans fluid is FAR worse for a good tranny than the new stuff could possibly be.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     

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