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? for automatic tranny guru's

Discussion in 'The Garage' started by Rockjunkies, Dec 4, 2002.

  1. Rockjunkies

    Rockjunkies 1/2 ton status

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    ? for automatic tranny guru\'s

    I had my Turbo 350 rebuilt and now it will not utilize 2nd gear at all. Even if you manually shift it, it will not engage. Also, there isn't any fluid running through the cooler lines. I pulled the lines off and blew compresed air through them to make sure that there wasn't any clogs in them. I checked my shifter linkage and it hit's all the detents for each gear. The governor is not sticking. The kickdown cable is properly connected and adjusted. The modulator is new and connected to a manifold vacum port on the throttle body. Tranny fluid looks good and full. The tranny is behind a 92 Tbi motor out of an 92 chevy P.U.

    Anybody know of something that I am overlooking? The guy who rebuilt it is a reputable tranny builder, so I would like to make sure that it is not something that I did wrong before I consult him. He rebuilt the tranny about 6 mo. ago, but I did not start to use it until last weekend. I also bought a new converter for it as well.
     
  2. BorregoK5

    BorregoK5 1/2 ton status

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    Re: ? for automatic tranny guru\'s

    Does it skip 2nd all together or hit it, slip and shift to 3rd? Was it working when you first installed it, suddenly go out, or slowly go out. At first guess it sounds like a valid tranny problem.
     
  3. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: ? for automatic tranny guru\'s

    In the Th350 rebuild manual the first few pages are about diagnosing problems and possible causes.
    If your tranny is only missing 2nd gear.... that is, 1st, 3rd and reverse are normal.... than that points to the intermediate clutch assembly...

    The good news is that is the first thing behind the oil pump cover if you want to try to figure it out. It should be pretty obvious what is the culprit of your problem. something won't be right.
    [​IMG]
    [​IMG]
    I've rebuilt my TH350 (and TH400 a few times)
    If second just started getting slushy and then slipping bad, then its possible that its just the cluthes and steels are burnt up but you'd probally be slipping in other gears as well and see dirty fluid in the bottom of the pan.
    If it was an all of a sudden type thing which it kinda sounds like, that isn't good.
    It could be something easy like the second gear servo piston is stuck, but i doubt it. You could check that by dropping the pan and the valve body. Being careful of the checkballs that will fall out!
    I would think one thing that could cause this is the seal might be bad (part# 12) but you'd be lucky if thats all it was.
    If i had to take a guess, i'd say something blew up(like part # 16& 17)- the intermediate clutch piston and piston return spring assmebly.... or ya blew up somthing like part # 26 the intermediate overrun clutch.
    That is like the 2nd gear sprag in the TH400 tranny which is supposed to be the weak link in a TH400 you can upgrade those from a 16 elemnt to a 32 element with double the amount of rollers in it. IF second only second gear goes out, it is usually that part.

    hope this helps.
    my 2 cents. /forums/images/graemlins/thumb.gif
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Re: ? for automatic tranny guru\'s

    Man that sounds an awful lot like a Sprag/ Intermediate over run. It's not really in second or third when that goes. It lets the drum (29 in the digram) spin the wrong way so your sort of in two gears at once.
    I wonder if the guy manged to put the spag in backwards? I bet it's possible. Been a few years since I was in my tranny but I think it's totaly possible and would be an easy mistake. Good news is if that's what happend there shouldn't be any damage it would just need the pump pulled and the sprag flipped over.
     
  5. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: ? for automatic tranny guru\'s

    Yup, it sounds like Grim brought up another possiblilty...
    I didn't really think about getting that overrun clutch in backwards, because in the manual it says to check that it spins one way and not in the other direction... seems kinda easy but it would be easy to get it in backwards too.
    It should spin freely in the counterclockwise direction, and lock on clockwise rotation.

    [​IMG]
     
  6. Rockjunkies

    Rockjunkies 1/2 ton status

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    Re: ? for automatic tranny guru\'s

    The tranny is a fresh rebuild. Unless it worked the first time I put her in gear, it has been that way since the rebuild. It does not hit second at all. It acts like a 2 speed tranny. If you manually shift it, first gear is fine. Shift it into second and it stills is hanging first. Go for third and it jumps right into third. Also, it will not down shift into second at anytime. I called the guy that built it, and he said it may be the roller clutch. But that still does not explain why there is no fluid flowing through the cooler lines. I am supposed to drop the tranny and take it to the shop so they can look at it. I am not looking forward to dropping that doubler out of there. I thought about dropping the pan and checking to see if it may be a stuck piston in the valve body. Any ideas what would be preventing the flow of fluid to the lines? Thanks.
     

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