HELP DIAGNOSE My 95 K1500 Trans issue..Im about to send it on down the road

Discussion in 'GM Powertrain' started by ohiomossyoak, Feb 20, 2012.

  1. ohiomossyoak

    ohiomossyoak New Member

    Here is the run down...I picked up a 95 K1500 Suburban a few years back.She had about 220k on the odometer then..5.7L(350) auto trans....After awhile it would occasionally not hit OD gear at cruising aint highway speed..First it only did it occasionally,then it became more consistent..It got to the point to where it does not even shift in OD now..Also cruise control does not work under these conditions.....Not sure why on that one....Now it wont sift down to 1st gear when you come to a stop..Unless I manually shift it in to down 1st,take off in 1stan then shift up..If i dont do this ,it will take off in what seems to be 2nd gear an once it his 3rd it shifts hard?It now has about 250k on it....I just dont know if I can fix it..Or if i should just send it on down the road
  2. carmantx

    carmantx Rockstar

    I am going to tag on to this thread. I am having the same issues with my 2000 K2500. No codes. I have searched and found information about the input/output sensors on the 4L80E trans. There should be 3 on yours, 2 on trans and 1 on transfer case. They are magnetic, and get covered in metal, and then can't send a good signal. Those are accessible from the outside, and can be taken out, cleaned, and then reinstalled. I am going to try that first. could also be throttle position sensor, or the valves in the tranny, that are easy to change if you pull the pan.

    Good luck, and if you find any solutions please post.

    Good news may be, that the tranny is not having a hard product failure. Could very well just be electronic.
  3. jake's silverado

    jake's silverado Epic Member 5+ Years 500 Posts

    So that was my first thought seeing there was no info in the post...
    Was it changed along with a filter recently? Did you do just a transmission flush and no filter change...
    Is there anything else you can tell us?
    With what you you have said I would take it to a tranny place for a free diagnosis/ Service it while it's there if you have never dome it or unsure what the previous owner did. When the pan is dropped, check for debris. Any time I have seen a tranny pan there has been some stuff but nothing major.

    Good Luck...
  4. ohiomossyoak

    ohiomossyoak New Member

    Fluid is at proper level when both warm an cold..An the smell of it seems fine...I have done no work/maintenance on the trans
  5. carmantx

    carmantx Rockstar

    Well, if nobody can help, I will post what I find while doing the diagnostics. I do believe it is electronic because of the cruise control not working at the same time. must be one of the sensors.
  6. Josh

    Josh Member 100 Posts

    That sounds like an electronic problem i had a jeep that disliked OD. changed a sensor on the vb and it was like new again. Id highly recommend replacing any sensor on it. and go to gm parts counter and get a good oem tranny filter and fresh fluid and flush it out as good as you can. though the fluid is clean the filter could be caked in clutch material dirt metal particles even bugs that got down in the dipstick tube possibly.

    ---------- Post added at 07:21 PM ---------- Previous post was at 07:17 PM ----------

    carmantx id clean em like you said. seafoam now makes a transmission cleaner. pour it in drive it then empty the tranny it cleans out everything cleans all the ball bearing pockets/pistons diaphrams. you could go to the junkyard and get a used computer (make sure its same type) and swap em. just my few thoughts also change fluid n filter with a good quality one. never buy the cheap stuff. i learned the hard way.
  7. ohiomossyoak

    ohiomossyoak New Member

    Do most of these recommendations pertain to the lack of going into OD? Is the not down shifting to 1st gear once stopped related?Or is that another part/problem...
  8. carmantx

    carmantx Rockstar

    If it starts of in 2nd, it may be in "limp mode". The electronics suspect a problem of some sort and it is protecting itself.
  9. carmantx

    carmantx Rockstar

    Ok Mossy, Update on mine.
    Today, I went and cleaned the connections at the throttle body, TPS, and made sure the connection under the dash was together good from the brake pedal switch. That connection was a little loose.
    I then got under the truck, and checked the connections at the transmission. Cleaned them all up a little. Found a few frayed wires, cleaned them up and double checked the connections.

    Got in the truck and headed down the road, with very nice, perfect shifts even in to overdrive. Hopefully, mine is cured. Point for you is, check all of your electrical connections, especially the brake switch.

    Good luck.
  10. jake's silverado

    jake's silverado Epic Member 5+ Years 500 Posts

    Good Job :great: and thanks for the write up/feedback on what you found. Boy, I was wrong...:money:.... and apologies if it caused grief!

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