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P0894 code trans comp. slipping

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Bigmacnchez, Oct 2, 2012.

  1. Bigmacnchez

    Bigmacnchez Member

    I have been trying to research this with no result. I have a 2005 1500HD 2wd 6.0 4l80e . after getting on the freeway and reaching at least 60MPH for 5 to 10 min my engine load and rpms will rise a little and the transmission will begin to shift hard and engine light comes on. I can turn off truck and start right back up and all is good or if I keep it under 60 it takes a lot longer to act up. On the back roads it has not messed up yet. All shifts are hard when it happens. I have checked the fluid looks good don't know how old it is. I don't have a tech 2 or a scanner that will test each part but wanted to see if their was a way to test each solenoid or the TCC with a multimeter or maybe someone has a option on what to do just don't want to do a fluid change and have to go back in I know it's probably an actual part that is bad.
  2. j cat

    j cat Rockstar 4 Years 1000 Posts

    being a 2005 vehicle and your unknowing of the fluid age , I would drop pan replace filter/fluid.

    using the now approved GM dexronVI. dexron III is a defective fluid , which is now not approved for these GM transmissions.

    sound like the transmission is slipping. then the harsh shifts. dexron III was dropped because after 10,ooomi it turns to acid. this then eats out the valves. then the pressure drops.

    too low a pressure you get harsh shifts.
  3. Bigmacnchez

    Bigmacnchez Member

    I bought some redline VI and filter will take a week to get I will check back
  4. Bigmacnchez

    Bigmacnchez Member

    Ok here is an update It's fixed. This is what I found The TCC and 1st to 2nd solenoid were bad, low and reverse servo was broken sun gear was bad , and the trans case was cracked by the servo housing and it was broke also. Rest looked good clutches were good. So with the case cracked I decided to build a better transmission 100% new. I bought a upgraded case all new parts I mean all parts from torque converter to rear seal. I put it back in with redline fluid topped it of put a tube of shudder fix. 2500 later it still did the same thing but not as harsh man was I mad. Then I put the tech tool back on it and read the code again as in part it says something about the harness so I checked it and it turns out one of the terminal's in the actual plug was burnt out. So today I got a new harness replaced it and now it run's awesome. Shifts are so firm and the overdrive is working no codes after 400 miles. I think when the solenoid's went out it caused a short in the harness and after time with the harsh shifting it started breaking stuff. I had a P0894 code trans would not lock up in over drive on highway and once code was thrown trans would shift hard in all gears. And another thing my gas mileage went from about 11 MPG to 16 MPG with trans fixed.:party:
  5. a.graham52

    a.graham52 Rockstar 100 Posts

    when a code like that sets, the transmission defaults to "max line pressure" which gives you the harsh shifts. its more of a limp home mode to eliminate as much "slip" as possible durring shifts. just an fyi for everyone.

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