Clunking transmission

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by guppy1999, Jun 28, 2013.

  1. guppy1999

    guppy1999 New Member

    I have a 1999 Suburban K1500. It has 147000 miles, and after driving it for 40 miles or more, when I come to a stop and start again, the transmission "clunks" into second gear, sometimes even third. I heard that a flush may solve the problem, that possibly it's sticky valves, but the local transmission place says it some rod and that its best if I replace the whole transmission. Ant ideas?
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Im not a transmission expert by any means but I have been around more than a few high mileage transmissions, and one thing Ive always avoided is flushing high mileage trans. It never works as planned and most times leads to trans failure sooner than if it were left alone.
    Just something else I want to throw out, are you sure its the trans doing the clunking? These trucks have been known to develop a clunk in the tailshaft of the trans, its a cheap and easy fix to ensure this isnt the problem.
    Theres 3 methods that havr been known to cure a trans tailshaft clunk.
    1. Pack the slipjoint if equiped and yoke with grease.
    2. Place a small rubber ball in the slip joint/yoke.
    3. Replace the yoke with a GM nickle plated yoke.
  3. unsub

    unsub Member 1 Year

    Never flush, but drain. On Burbs it's recommended to change tranny oil at so and so miles. Never flush though, just drain and change the pan/filter. Made a noticeable difference in my ride. When I changed the old tranny oil it was bad(almost stunk), it needs to be changed especially if it's been hauling alot of weight consistently. You really want to look at cheaper fixes first before committing to a new or rebuilt tranny. You can find a rebuilt for a good price but labor is a killer unless you have a good affordable mechanic.

    My acceleration "clunk" stopped after about 10 miles of driving after I replaced both u-joints. I've also heard of a nickel plated yoke replacement that has helped the clunk fix but IDK. While you are tinkering down there make sure your rearend fluid and cover is changed and look for metal pieces around the magnet inside, hopefully there are none or not a lot.

    tbplus10 has you covered, that yoke replacement or even just greasing it up good in and out has been a fix for some.

    Please post back when you find out what your fix was.
  4. Jeepman

    Jeepman Member

    Flushing a NEGLECTED transmission will make it go sooner. If it only has high miles and has been maintained then flush it. My last Jeep was owned by me for 285kK of its 325K. I flushed it annually after plow season with never an issue. I even plow snow and rock crawl with it. I junked the truck 2 years ago due to rust.
  5. unsub

    unsub Member 1 Year

    Drain and replace filter/pan, no flush. Not that spendy and if you plan on fixing the tranny anyway if by some rare chance that tranny fluid drain loosens up some gunk or metal that in turn damages your tranny most likely your only loss of cash will be the tranny fluid you just stuck in as tearing apart the tranny is going to cost the same no matter what.
    I do agree there is a slim chance one could cause more damage doing this but unless you commit to tearing apart your tranny you only have this choice or to do nothing at all and live with issue until it gets to the point where you have to tear it apart anyway. I'm not sure what real maintenance of a tranny would be other than changing fluid and even if one does a carfax type check that may not tell you if the auto's tranny fluid was ever serviced or not. If you have nasty disgusting tranny fluid you have to change it.

    Original post is from June so I imagine they have already decided on this. lol Fact that this was the person's only post probably means they don't even have the Burb anymore. This is my main pet peeve with forums, many never come back to update, they only want answers and sometimes they don't even listen to them.

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