Late shift issue and 4wd screwy

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Willow, Aug 3, 2013.

  1. Willow

    Willow Member

    First now solved, but just thought I would post this so others may have some info. My tranny and transfer case was replaced last winter. Both failed as when transfer case went out, it took tranny with it. I knew the transfer case was on borrowed time as it was cracked 2 yrs before when my husband had the truck (don't get me started). I kept it going by making sure I kept the fluid level up. Anyways installed used replacements as I had saved up enough for transfer case, but was not expecting tranny to go with it. Pulled them out of a truck with almost 100,000 mi that a tree fell on. Son installed. He made a few errors (like switching 2 wires, not securing wires well and them getting damaged as a result, linkage not quite right) and still had a couple other issues that I was working on solving as I had time/money as at least it moved. The last 2 issues are late shift and 4wd screwy. The late shift probably wouldn't have been noticed by most, it was only about 500-1000 rpms off- worse number when first starting- but I am very attentive with my truck. Parts were cheap...transmission solenoids. I had him replace those today. Shifted at right rpm's on way home after truck sat for hours. While he was working on that I took out the 4WD selector switch to check that. Solder looks fine, so put it back in. The issue with that is when you put it in auto, it engages but then light will blink and it disengages and gives service 4WD message and does not come out of 4wd (high, low or auto) without shutting off truck and restarting. I took it in to tranny shop and they cleared code, it was something generic. They wanted 600 to take it apart and find issue....umm no. Has not coded since, but still does not come out of 4wd (high, low or auto) without shutting off truck and restarting and not sure if auto is still engaged or not as it has not been slick out since then. I am still not convinced it is NOT the selector switch as this is the original (2002) and I know these can have issues with solder cracking. I did not take the circuit board out to check back for cracks, as I was not sure if it would break it (and I had no other way to auto parts store). I had an actuator go out on old tranny and replaced that once....but that time 4wd would not work at all. Since I can wait to use 4wd until the winter, I have time to figure it out.
  2. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the switch issue is the switch pins were not soldered correctly. the solder joints are cold solder joints and this is why after a period of time the switch will throw a code. now if you get a 4wd message light go to a transmission shop that can read GM specific drive train codes. then get that code and post here. don't need any engine codes just drive train . and this will be a very expensive code reader not some $200 part store unit.

    normally when the light keeps flashing this would mean a wiring or encoder issue.

    the switch is always being checked by the computer so if the switch is with , bad solder joints it will throw a code. this is because the computer does a circuit check. on shut down it resets.
  3. Willow

    Willow Member

    Yes, I did that before. He just reset and did not pin point issue. I'll just replace the switch, can do that myself and only $50 after coupon code.

    - - - Updated - - -

    OK...drove an hour out today and on my way home it clinked and shifted hard into 3rd...did another hard shift one other time on way home and rest of time- perfect. Can't help but wonder if it is the parts I just had son install. I noted they did not have screens on them like the old ones. I could not find a way to remove the screens from old ones to put in new. So I am wondering if something got sucked in and caused a brief issue....but hard to imagine anything being sucked in so soon with new tranny fluid change and cleaned out pan completely of any shavings. So maybe I should have son just put old ones back in...the shift was not off much. Thoughts?
  4. j cat

    j cat Epic Member 5+ Years 1000 Posts

    hard shift into the higher gear would be high pressure being commanded due to slippage being detected.

    could be the valve bodies are worn. this can happen when dexron III is used and you go more than 30,ooo miles on the tranny fluid replacing. DEXRON III turns into an acid .

    use the now approved GM dexron VI.


    with metal in the pan this would indicate the shell is damaged. this will cause hard shifts at first since a cracked shell will cause a loss of pressure creating a slippage condition.
  5. Willow

    Willow Member

    Shell damaged? Inside? Figured out that issue- it was one qt low on tranny fluid. Oh gosh I think we put in dexron 3. I will have to double check my receipts. I am going to start a new thread on current issue. I swear I am getting weary of these issues!
  6. j cat

    j cat Epic Member 5+ Years 1000 Posts

    you just had the transmission pan dropped ,cleaned, and replaced fluid how could it now be 1QT low ?

    are you doing these things or your just reporting ?
  7. Willow

    Willow Member

    My son screwed up...he thought there was 5 qts in a gallon.
  8. Willow

    Willow Member

    Thought I would give and update and verify a part number. After replacing the 4wd switch on dash and the actuator, took back to tranny shop today to see if they could get a code that would tell me what issue was. They did. Said the rear speed sensor on the transfer case is not reading at all, front one is as is the ones in trans. Said could be loose wiring or bad part. Wanted me to schedule appt to check wiring and replace part if needed. I took it to my mechanic to check (he doesn't charge to check things out) and he said wiring was fine but the terminals were spread and could be causing to not make contact well enough. He adjusted them and said to try it. Same issue, so apparently sensor is out. Stopped at Advance Auto and they pulled up list of speed sensors but not sure they selected right one. They gave me part no S8365 sensor Which says it is for 4wd and RWD...if RWD it would not have a transfer thinking this is one for transmission. If that is the case- which part no do I need? I am planning on replacing both on transfer case at same time- seems the logical thing to do, I would imagine both are same part#?
  9. j cat

    j cat Epic Member 5+ Years 1000 Posts

    what you need to do it get the drive train failure code and post here. then we can tell you whats going on or a much better idea. there are three speed sensors. 2 sensors are on the front hubs. the 3rd is in the transmission thats it ..

    so anyway post the failure code. you / they must have a GM drivetrain code scanner. autozone and some tranny shops may not have the proper tool..........................

    my guess is the people that replaced you transmission and transfercase are hacks. wiring is most likely damaged along with connectors .

    good luck your gonna need it when idiots mess up the wiring on these. the wires are very small and break easy ///too easy........
  10. Willow

    Willow Member

    They did not give me a code. He hooked up the "scanner" and took off with truck. On return, said when put in 4wd auto he saw that "the rear speed sensor on the transfer case" was not being read. I heard him explaining the guy at the counter who was writing up the paper work. He said he could see the signal going to transmission speed sensor, to front speed sensor on transfer case but not rear. He did not give me a failure code nor was one written on paper work. This was Russ Moore Transmission shop. assuming they have the proper scanners. As far as the people who replaced my transfer case and trans...yes- my son is not a certified mechanic. Yes, he made some errors (already fixed a couple that was found). It was the best I could do at the time. I was prepared for transfer case to fail, but was not prepared for it to take the tranny with it, so did not have the money to go the route I normally would have gone with engine or tranny issues. So paying for it all now. What's done is done. Now just trying to get Brutus back to normal.
    Last edited: Sep 25, 2013

Share This Page

Newest Gallery Photos