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4L80e problem?

Discussion in 'Chevy Trucks' started by old skool, Jan 10, 2010.

  1. old skool

    old skool Senior Member
    from NW IL
    Messages: 167

    I have a 97 Chevy K3500 with a Boss 8.2V. The truck just turned 100,000 miles. I love the truck and everything is fine, until I leave the truck set a day or so.

    Sometimes (not always) when I take off in the morning, the trans feels like it is slipping, like its low on fluid. It is not. I changed the fluid this summer. Then in October, I completely changed the fluid and the filter.

    Someone said they thought the converter might be draining back? Where? into the trans?

    Any thoughts/suggestions?

    Also , when plowing, where is the selector lever best kept?

    Thanks!
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    How long do you allow it to run before driving off? If it idles for a few minutes beforehand does it still do it consistently?
     
  3. old skool

    old skool Senior Member
    from NW IL
    Messages: 167

    The truck is in a heated garage, so I never really allow more than 20 or 30 seconds before moving it outside. Then I usually drive around 30mph for a couple miles before reaching a highway. This morning the truck was fine. Again, I notice it most if it sets for 2 or 3 days without driving it.

    Once moving, it really isnt a problem, there might have been a time or two where it would be a little slow to shift into gear, but as a rule you hardly ever notice it after its warmed up and running. Even when plowing you really dont notice any slippage.

    I'm just concerned if I have a problem in the works? Is there anything I could be doing differently?
     
  4. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    For gears to use when plowing, use only [1] & [R]. This will keep the reverse band applied. It only takes a little while to get used to shifting all the way to [1]. The reverse band is the weak link on these trans, so keeping the band applied continuously will reduce the cycles on it.
     
  5. old skool

    old skool Senior Member
    from NW IL
    Messages: 167

    I used to plow with my old TH400 in low most of the time. ... I think I was told that ,maybe for the same reason?

    In light/fluffy snow is it ok to let the 4L80e upshift into 2nd?/ or should I slow my ground speed down a little, and/or run a few more engine R's on the longer runs?
     
  6. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    The second reason to run in [1] is also to prevent the [1] - [2] upshift at the end of the run when you let off the gas. Shifting generates heat and causes wear to the clutches. You need to use a little judgement when to hold in first or let it shift. I almost always stay in [1]. The extra revs won't hurt the engine a bit. Plus you get extra cooling on transmission because of the higher RPMs, the extra revs help the alternator too.
     
  7. old skool

    old skool Senior Member
    from NW IL
    Messages: 167

    Thanks for the input on the 1st gear plowing! Will definately try that.

    Back to my trans, is there anything really bad going on? Can the converter drain back after setting? Does it drain into the trans? What would cause that? Any easy cure?
     
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Yes the converter fluid can drain out of the converter and back into the pan. It will also drain out of the cooler and cooler lines as well. However, this should be all re-filled within 30 seconds after starting the engine and if it wasn't you'd know it right away becuase when you engage any gear it wouldn't move for a brief period. Sounds more like a leaking shift valve or slow/weak pressure control solenoid at this point.
     
  9. old skool

    old skool Senior Member
    from NW IL
    Messages: 167

    Thanks for all the input guys.
    The truck seems ok once the trans gets fluid pressure. .Sounds like the best I can do for now is to start using low gear for plowing and maybe start saving some coin for an eventual rebuild?
     
  10. damian

    damian Senior Member
    Messages: 330

    trans leakback

    could also be leaking back from a bad filter seal in the pump housing he may have installed a cheap aftermarket filter kit and this problem may have started after that.this will cause air to leak in while sitting causing fluid to drain back thru valves or pump bushing etc.
     
  11. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    2COR, can you help me understand what you mean by keeping the reverse band applied, in 1st? Also, how does higher rpm help cool the fluid? We have clutch fans for cooling, the only way I see higher rpm helping is by faster vehicle speed, which isn't going to be much when plowing, at least not in 1st gear. Are you saying the higher rpms will pump the fluid to the cooler faster? It just feels to me like lower rpms in 1st would keep temp down better than high rpm. I've seen auto trannies killed by running them in 1st too long. Not trying to argue here, just trying to wrap my head around it.
     
  12. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I'll do my best Dan, Mike may have some to add. I'll admit my knowledge about these has been learned over the last year or so. Some came from my trans rebuilder last January, some came from my reading here, most from a friend who knows these things inside and out:D

    The reverse band is actually the Low/Reverse band. It is applied in both Reverse and Low/1. I don't know the technical jargon, but the drum the R/L band holds stationary provides reverse, and compression braking in First. The R/L band is not applied in when you select [D].

    Needless to say, when plowing we are constantly shifting in and out of reverse. Each time we shift from [D] to [R] pressure is applied to the R/L band. This repetitive cycling actually fatigues the metal in the band till it breaks. By shifting quickly from [R] to [1] and then back to [R] at the end of the run, The R/L band recieves continuous pressure greatly reducing the cycling.

    As for enhanced cooling, by staying in [1] engine RPMs stay higher. This provides not only increased trans fluid flow through the coolers, it also will provide increased engine coolant flow through the radiator, where one of your tranny coolers sits. The extra RPMs also make it easier for the alternator to keep the battery charged.
     
  13. old skool

    old skool Senior Member
    from NW IL
    Messages: 167

    Intersting stuff. I might check with a guy that has rebuilt a 700 and a 4L60 trans for me to get his suggestions. He works for a GM dealership and builds trannys for race cars and mud trucks on his own time.

    damien, more good info, We used a NAPA filter kit. I bought the truck a couple years ago with 80,000 miles on it and the trans had started doing this prior to the change.