904 Trans suddenly stopped working

Transmission and Drivetrain Tech

  1. Randall Hendricks

    Randall Hendricks Member

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    Well as the title says my 904 trans lost every gear. This is a project car, the car sat for years and years and years so I drained the old fluid and replaced the filter. 2500 stall was added and I filled up the converter before I installed it back into trans. Topped off trans and then started car. Continued to check and add fluid until it was finally completely full. Put it in reverse and reverse worked. Put it in 1st and 1st worked. Drove around the yard a little and everything worked. Backed car into the shop to adjust idle some more with car in gear and suddenly no gear worked. Not reverse, 1st, 2nd, or 3rd. Linkage is hooked up and working as it should. Finally ended up dropping trans pan and noticed a bunch and I mean a bunch of metal flakes. So I am completely confused how the trans can lose every single gear like that. The only thing that comes to mind is the first time I started the engine I heard a whining noise, but it quickly went away and never heard it again after that. Any ideas on why all of the gears are now not working? Picture of metal shavings attached. I was told that the converter should have spun freely before attaching flex plate to converter, but I had to use a screwdriver to turn it. Assuming that probably messed something up and cause the whine? Either way it's weird that it worked and then suddenly didn't.

    IMG_0933.jpg
     
  2. MoparMike1974

    MoparMike1974 FABO Gold Member FABO Gold Member

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    Your converter should not have been that tight. My guess it that it was not fully seated and you either ripped off the tangs on the converter or damaged the pump. Thats a hard and expensive lesson but I bet you only do it once.
     
  3. KickDown

    KickDown Just a Brit in Germany

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    I think Mike has a good point there. I've seen this happen many times & definitely not a nice thing to happen. Maybe a bit late, but for future reference, here are 3 photos of a correctly fitted 904 converter before the transmission was installed. The distance between the starter ring gear & the bell housing flange is 34 millimetres.

    38905016tz.jpg
    38905037rm.jpg
    38905061bv.jpg

    Hope it helps.
     
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    • Randall Hendricks

      Randall Hendricks Member

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      I think you are correct. The converter did spin freely until I got the trans and engine mated. So maybe it was all the way back even after the 2nd "clunk". It definitely sucks, because it was a brand new torque converter. But, can't buy experience. Won't let this mistake happen again.
       
    • Randall Hendricks

      Randall Hendricks Member

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      Based on the pictures it seems like my converter was close to being in all the way, I was probably only off by a few millimeters. It spun free after it slid in to the 2nd position. Maybe I just didn't push it in far enough even and it was only slightly in place.
       
    • MoparMike1974

      MoparMike1974 FABO Gold Member FABO Gold Member

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      If you look at the picture above, you can see the converter lugs are in past the mating surface of the bellhousing. The picture shows the converter all the way in. Keep it like that until the trans is bolted up to the engine. Then the converter should slide forward to mate up to the flex plate. It should slide forward with very little effort.
      Usually if you hear the second klunk you should be good to go. All I can say is pull it down and start inspecting parts.
       
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      • 408 swinger

        408 swinger FABO Gold Member FABO Gold Member

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        What year and cubic inch is the trans behind? Early small block had small rear crank registers. Thus, your convertor hub gets "jammed" into the back of the crank.
         
      • Randall Hendricks

        Randall Hendricks Member

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        I will have to check, it's a 318 and off the top of my head I thought it was a 73 block. The converter freely spun all the way up until I mated the trans to the block and THEN it didn't want to spin by hand anymore. Which is why I figured the converter was in all the way and that was just normal. When I ran the part number on the crank it came back with the crank that was used in both the 318 and the 340 for a very short period of time. Not sure if that is in fact my problem or not. Maybe the hub is just big enough to bind inside the crank?
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        I'm betting the convertor is Ok.
        I'm betting the sprag is bad or
        but it doesn't really matter; with that much metal in the pan, it;s gotta come down for a looksee.
         
        Last edited: Jul 2, 2020
      • CudaFactHackJob

        CudaFactHackJob FABO Gold Member FABO Gold Member

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        I always measure from a straightedgeacross the bell housing back to the pads; then from the back of the flexplate to the block; making sure the trans measures larger. Your pump is gone. You'll have gears when it's cold for just a minute.
         
      • Charrlie_S

        Charrlie_S Well-Known Member

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        I'm betting the front pump is gone, because the converter was not seated correctly. When the trans is bolted to the engine (should not have to pull trans up with the bolts) there should be space between the flex plate and the lugs on the converter. Normally you should be able to turn the converter, easily, and/or move it in and out of the trans about a 1/4 to 3/8 of an inch.
        In my early days I had a converter that was made too long. It was fully seated in the pump, but there was no play. It was tight against the flex plate. Made one 1/4 mile pass, stopped to pick up my time slip, car wouldn't move. The converter was made for use with a "block plate".
        I contacted the converter manufacturer (Fairbanks), which is no longer in business. They were the ones that told me what was the problem, and owned up to the mistake (didn't blame it on me for not checking when installing). Made me another converter, and gave me every part I needed to repair the trans (even the fluid), no charge.
        PS: This was Frank Lupo, back in the mid 70's, who is/was owner of Dynamic converters.
         
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