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Thread: torque converter street/strip

  1. #61
    Registered Member chasracer's Avatar
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    Yep - do it now, its not going to get better on it's own. When you swapped your hard parts to the new case you did check all of the clearances? I mean it's basically a rebuild at that point with a soft kit. Reputable converter builders flush out the units with a flushing machine (even my local trans builder has a converter flusher) and normally bolt up the units to a mule engine for test. Leaks are usually done with an air adapter and water. Before reinstalling the converter either get it flushed locally or do it at home. I have poured mineral spirits in, sloshed it around good and then let it sit upside down on a plastic bucket to drain - sometimes over night. I repeat until I am satisfied that nothing else is coming out. Normally you might see a little bit of what is in the pan the first time, any more than that raises a flag for me. Last - how much clearance was there between the converter mounting lugs and flexplate during installation?

  2. #62
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    Clearance at the flex plate was 3/16", I had considered shimming with washers since that was the recommended max (I thiink), but didn't.

    The only local transmission shop doesn't have a flusher. He sells everyone a new converter if they want a warranty.

    I just tore it down and can't find a speck of metal anywhere besides what you saw in the pan. Don't see any damage to any bushings, thrust washers, gears, anything. Certainly the amount of metal in the pan would have showed up somewhere. Would you say (or guess) that it had to come from the converter?

    Are you saying the amount of metal I found is almost common or it's a big red flag?

  3. #63
    Registered Member chasracer's Avatar
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    The 3/16" clearance on the lugs to flexplate is good and would not be part of the problem then.

    Looking at the picture again of the oil pan, the amount of metal is not "killer" but when we combine it with the noise issue then you have to wonder if something is tearing itself up. I would take a good hard look at the planetary and make sure that all of the gears are perfect, that the clearances are good and there is nothing else that might be failing - such as the sprag. After that I would concentrate on the pump. The minimal pressures that you recorded along with the fact that you put a heavier aftermarket relief spring in the pump just doesn't add up. Again, I would check the pump gears for issues, their clearance and make sure nothing else is out of whack. Make sure the stator is where it is supposed to be in reference to oil hole alignment. I would also still verify that the surfaces of the valve body and it's mounting surface are dead flat and free of any burrs. Correct valve body gaskets? Check balls in the right spots? I would flush the converter a couple of times, use a paint strainer but I think you will be okay there.

    Just for info - I shattered the rear thrust bearing on the TH400 in my Chevelle one time, it didn't take any time at all to turn the fluid into aluminum paint as the gear train moved back and started shaving the rear of the case. I had my machinist cut the rear output for a Torrington bearing which fixed the issue and I never built another TH400 without doing that same procedure. But even with all of that aluminum floating through the entire trans and converter, it didn't hurt anything. Biggest deal was just cleaning it all up with a lot of brake cleaner. The metal you have came from somewhere but stayed in the bottom of the pan - just need to try and find where it came from.
    Last edited by chasracer; 09-09-2018 at 12:14 PM.

  4. #64
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    Note the thrust washer stuck on the front. Should it be there? It wasn't. Without it, it looks like the various oil passages could have been off their mark. Enough for lower oil pressure? By the way, out of two transmissions, I only have one washer that size. I'm pretty sure it was missing in the donor trans.
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  5. #65
    Registered Member chasracer's Avatar
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    Yep - it's supposed to be there - bet you just figured out the low pressure/whining sound!

  6. #66
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    I've done it before but I'm no expert at this as you can tell. This last time I took pictures as I took the donor trans apart. Dumb move, I should have done it to the one I knew was working before the case cracked.

    FedEx is supposed to pickup the converter tomorrow, should I rinse it out and cancel the return? I know there is no definite correct answer, just asking for opinions.

  7. #67
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    There's no way for us to know. It's probably OK with a flush. But we have no way of knowing.

    You need to check and adjust all the thrust clearances. They can definitely change with a case swap. I'll bet you can find all the thrust info on the internet. But you certainly can find it in the Ron Sessions book on TH400 transmissions. A missing thrust washer could definitely cause your symptoms. You might be lucky to have caught it before everything was trash.

    Did you put new clutches/steels and sealing rings in it? Especially sealing rings. And you need to air check the sealing rings (procedure in the book).

  8. #68
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    Yes I have the Ron Sessions book and go by that. I had completely rebuilt it just a couple years ago and really don't see the need for a complete rebuild.
    Tony

    1955 Bel Air Sport Coupe

  9. #69
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    It's possible to break a sealing ring during assembly, or if using plastic ones, just have one get out of place. You won't know until you have a look.

  10. #70
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    Oh, those rings. I'm using the steel/cast ones. I thought you meant the rubber rings for the piston/clutch pack things. I have no luck getting them in and last time had the local shop do one of them for me. The cast rings all look OK. It really worked GREAT until the case broke.
    Tony

    1955 Bel Air Sport Coupe

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