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Stall converter wear on drive hub

Discussion in 'A Body: Duster, Valiant, Dart, etc' started by core, Oct 21, 2015.

  1. core

    core Member

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    I have a 360 block, B&M stall converter and flex plate attaching to a 727 automatic transmission.
    The tranny has been rebuilt and the moter is new. Less than a 1000 miles.
    In the spring I noticed tranny flued dripping, so I brought it in to be checked. The B and M converter had signs of wear on the drive hub and the seals on the tranny pump where bad.
    I had all the failed parts on the tranny fixed and the converter's hub replaced.
    Just last week I noticed tranny flued again under the car. I brought it back for service and it was the same problem as before. Stall converter is junk and the tranny seals are worn.
    Would anyone know what could be going on?
    Do I have an alignment problem or a bad trannsmision guy?
    I called the person who built the motor for some insight. I asked if the crank could be to blame, but he didn't think so.
    Can a crank wobble enough to cause the converter to move around inside the tranny and cause this damage?
    The tansmission slid over the dowel pins and the bolt threaded in with no resistance.
    thanks
    Core
     
  2. dana44

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    I would guess the bushing in the front pump is worn. The bushing is like a cam bearing and usually doesn't wear very much, but if it had it could allow the torque converter to move around the input shaft a little bit. Some rebuild kits replace the bushings but it isn't normally done. Can't say as I have heard of a problem with this bushing, but I have had to replace front pumps because it wasn't working efficiently and the fluid would burn after one hundred miles, but not a difficult replacement. As far as the flex plate goes, the hub of the torque converter sits inside the center of the end of the crank so it would be centered that way on that end.
     
  3. ImperialCrown

    Level III Supporter

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    Agree. We generally replaced both the converter and front pump assemblies when these were worn.
     
    floridaman2013 likes this.
  4. core

    core Member

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    As far as I know the transmission's pump,bushing and seal had been replaced at the first break down.
    If I have a out of balance crank could that create this problem?
     
  5. 68RT

    68RT Well-Known Member

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    Yes. External or internal balance is important with a 360.
     
  6. core

    core Member

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    The block is a from a 360, but the motor is a 408 stroker internally balanced. The stall converter and flex plate are for an intenally balanced set up.
    I was told that if get the balancing wrong there would be lots of vibration.
    has anyone heard of a crank moving around and causing this problem?
    If the crank is moving around wouldnt the main rear seal leak?
     
  7. ImperialCrown

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    The crankshaft itself is fairly rigid, but I have driven some cars with imbalance issues before.
    Question: Does your car vibrate noticeably while the engine is running?
    I don't think that the crank will 'move around' but if the heavy torque converter sets up a vibration, I can see that being a big problem.
     
  8. pt006

    pt006 Active Member

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    core; the engine must be a torque monster! Be aware that some aftermarket flex plates made for 360's had a balance weight welded to them so that a neutral balance torque converter could be used. A bent flex plate would cause the converter to wobble and take out the bushing/seal. With the converter unbolted and pushed rearward, there should be enough room to get a dial indicator near the bolt holes to check the run-out of the flex plate.
     
  9. core

    core Member

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    The motor does move around. The coins in the ashtray vibrate and move.
    I installed a B/M neutral balanced flexplate and stall converter.
    All my research is pointing to an alignment issue.
    I need to check the dowels on the block for wear.
    Also the Harmonic balancer I was told that needs to be neutrally balanced as well.
     
  10. ImperialCrown

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    Straight and offset dowels are available for Torqueflite bell-housing alignment issues. Are the dowels even there? I had a car once that didn't have the dowels re-installed before bolting the transmission back in.
    The harmonic balancer shouldn't have enough mass imbalance to shake a car.
     
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  11. pt006

    pt006 Active Member

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    core; 360's come from the factory as an externally balanced engine. They use a harmonic balancer and a torque converter weight to accomplish this. A stock 360 balancer has a cast-in C shaped depression in the outer ring of the harmonic balancer. It should NOT be used in a neutral balance crank assembly. I believe a 318 balancer will work. They [the factory] added an additional specific weight in a specific location to the 360 torque converters. This weight may be removed to make the converter neutral balance. Make sure you know which weight to remove if there are 2 weights.

    This info should have come with the crank kit!
     
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  12. core

    core Member

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    I checked the harmonic balancer and it is a neutrally balanced, but weights can be added if needed. The transmission mechanic checked and no weights have been added to the balancer.
    He lined up the dowels and noticed that one was pushed into the block and only sticking into the tranny a little. He had a machine shop make new dowel so they push deep into the transmission.
    Waiting on the new stall converter to arive so it can be mounted to the flex plate.
    Before reinstall the tranny he wants to turn over the motor and make sure everything is balanced.
    Is there anything ealse that should be done before everything gets installed?
     
  13. pt006

    pt006 Active Member

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    core; On the stock 360 harmonic balancer; there are no weights added but weight is removed in the casting process of the outer ring. Probably hard to see when the pulleys are in place. But turning the engine over [ratchet] and 'feeling' for the indentation might work.
     
  14. AC TC

    AC TC Well-Known Member

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    Check alignment between engine and tranny like imperial said. Its a vital key to smooth running and long life of converter and tranny pump.
    Is the "cup" ( pilot bushing??) for the converter in the crank?
     
  15. core

    core Member

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    Still needing some help with this problem. Been through two more B/M converters since my last post. My car is sitting at the transmission repair shop right now and we are stumped. Last spring I swapped the transmission case thinking that some how the one I was using was bad. Ive been driving the car like an old lady and the problem came back again this spring. The convert and pump bushing get destroyed after 4 months of easy driving. In those four months I only drove the car for a few hours a week.
    I found a guy who is going to check the alignment of the transmission and motor. It seems to me that if the
    Has anyone heard of an automatic transmission and motor being so far out of alignment that it would cause this problem?
     
  16. 68RT

    68RT Well-Known Member

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    Yes, but rare. Make sure that the nose of the convertor fits the diameter of the pocket bored in the back of the crank. Just as important as aligning the transmission to the block.
     
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  17. dana44

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    You can also start checking things like centering with a dial indicator. Mount the base of the dial indicator to the block and check the center of the crank. There should be a machined ring of some sort, check to make sure it has no run-out (out of round) by putting the needle on it ad rotating the crank slow enough that the needle can be watched, to which it should only move .0015 plus or minus the original number on the dial when set up. Also check the center hole diameter to the torque converter size, make sure it is sitting inside properly.
     
  18. core

    core Member

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    Today the transmission was taken apart and bolted to the block for an alinement check. The alignment was 40,000 off. Offset dowel pins where installed to bring the aliment to 6,000. A more acceptable range.
    I'm hoping this will solve the problem.
    Waiting on a new torque converter and then a test drive.
    I believe the car's vibration problem was also caused from the misalignment
    If the vibration is go then then the problem should be fixed.
    I'll post again after the test drive.
     
  19. dana44

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    Yes, a .040 offset on the center of the hub is a LOT. This doesn't happen very often, but glad you were able to get the issue identified first, and yes, it should fix the vibration and torque converter issues you have had.
     
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  20. core

    core Member

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    Just one last question on this problem. What would have caused this aliment problem?
    Was the block always off or did the machine shop cause this issue?
     

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