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 New Member

    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 New Member

    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 New Member

    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 New Member

    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 New Member

    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 New Member

    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 New Member

    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!
  11. carmantx

    carmantx New Member

    No grief for me Jake. Hope the OP has a good result, but sounds like his has gone to limp mode. Could still be electronic. Since the OP mentioned the cruise control did not work at the same time, I suspect something with the brake switch. The brake switch also controls the lock up on the convertor. It the switch is indicating it is pressed, then the convertor won't lock up and the cruise control would not work. I don't think the trans goes in to overdrive until the convertor is locked up. The brake lights are operated by separate circuit. And, no codes because the switch thinks it is being depressed, not a malfunction.

    My .02.
  12. Josh

    Josh New Member

    my 94 k1500 had the vss finally go bad on it yesterday. the symptoms i had weeks prior was strange shifting all of a sudden. revving up like its slipping. i went to go to doctors that morning all was normal. shut it down at gas station. took back off after leaving and romped on it. suddenly the truck read 40-50-55 then started moving left to right. tranny started shifting in and out of 2nd 3rd. finally it only wanted to read 30 maximum so i couldnt automatically shift into 3rd. if it did it would automatically kick back into second. eventually the speedo read zero. you know what that means. First gear all the way home. i could manually shift into second to. got the part for it. took it off with a one inch wide adjustable wrench. found metal shavings on mine, its a magnet like carmantx said. all was back to normal.

    ---------- Post added at 06:55 PM ---------- Previous post was at 06:51 PM ----------

    reason i said my symptoms is for the OP to see if there is any matching symptoms. Seafoam makes a Transmission cleaner now. its a pour it in. run it for however long and when you change the fluid all the varnishy gunk built up get put into the pan when needing to be changed. if carman had good luck cleaning all of his connectors. that would be my first step. go cheap first then spend money. my .02.

    ---------- Post added at 06:56 PM ---------- Previous post was at 06:55 PM ----------

    Did you use an automotive Electronics cleaner and re dielectric grease everything or? i may do this to mine just to make sure everything is top notch on my truck
  13. mattheww

    mattheww New Member

    I have a 95 C1500 with 124,000 doing the same thing with OD. No problems in any other gear. Im pretty sure my VSS is bad, but probably going to go ahead & Flush & replace filter as well. Let me know what u figure out & i will do the same
    I have a post up about it as well if u want to see if the symptoms match up.
  14. dipstick

    dipstick New Member

    Okay cruise also goes out..how about speedo does it work good all times? If you have a tach does it work?
    Do you have a abs light on? Brake light on?
    Quiet a few things in in the system...tps..ecu/ecm..abs sensor ..vss..tps...speedo..tach...cruise..brake switch...95 may have a drac..converts analog signal to digital..for ecm to read.vss
    Try this while driving pull upon brake pedal with your foot ..see if shifts better.
    Most times prob. will be in wiring harness.
  15. Josh

    Josh New Member

    you may be having a faulty read on the vss. pull it out and see if its covered in gunk. the one i pulled out of my trans had gooey metal shavings attached to the magnet. my guess it couldnt no longer read. i had hard rampant shifting. in and out of gears violently. no shifting from first to second unless manually first to second and drive. when the speedo finally quit reading it only had first. changed it out and bam she drove like it never had a hiccup. its located on the transfer case also take the ecm connectors off clean them real good and reconnect. might have a stored code causin hell raisin in there.
  16. ohiomossyoak

    ohiomossyoak New Member

    Tac is good speedo good...Brake light is on but has been prior to any issue..I will try the things listed
    Thanks for the tips...I will give them a try
  17. The Heater

    The Heater New Member

    Hi, Ohiomossyoak:

    I know that not everyone on the forum is in a financial condition the same as maybe others are, and that any repair may be difficult to manage financially if it means taking the vehicle to a repair shop. I am blessed with a good job and a wife who also earns a lot of money, so we can just take our vehicles to a shop and get an opinion. I also have established relationships with several local shops so I trust them when they tell me I need something done, and not everyone has that type of thing "sitting in their back pocket". I have a client or two in the automotive industry, so of course I can just call them to ask questions.

    But when it comes to transmissions, unless you have prior experience with automatic transmission repair, at some point you have to admit personal defeat and ask for help from a professional who knows what they are doing, not just post a question on the web. It is not a bad thing to ask for someone to test drive your rig and tell you their opinion. It will save you a lot of time.

    Certainly, you can, as you say, "send it on down the road" by unloading the truck on someone else. But if the truck has otherwise been good to you, why not ask for one or two professional opinions on what is going on?

    The problem I see here is that you noticed the problem when it was not very acute, yet instead of doing the logical thing and taking it in to a repair shop at that time, you continued to drive it, which in most or all such cases will only exacerbate the problem, and when the pain becomes too inconvenient to go on, you now are facing a much bigger financial obstacle to getting it fixed. We all make choices, and we must live with the consequences of our choices.

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