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Thread: Transmission Woes

  1. #11
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    Quote Originally Posted by chasracer View Post
    The old ones - the one's I consider the good ones have 8 bolts in them. The later stuff has 6 bolts. AS long as you don't mix the pump halves all is good. And TH400 cases usually don't crack so you have something going on that is causing that stress to occur between the engine/trans mounting and the transmission mount. Something is flexing and moving. In the Camaro we used to crack TH350 units on a regular basis, anti-roll bar in the back finally cured that problem because the chassis was twisting so badly.
    My thoughts exactly.

  2. #12
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    An easy question, I think? The pump seal has leaked since I had this trans and I was beginning to think the case was cracked down near the bottom (it wasn't the front pump seal). Anyway, what exactly seals that from leaking? Is it the paper gasket or the large round rubber gasket? Oh, and yes I have new pump washers also. Working on taking it out today.

    Also there was a good amount of fuzz on the drain plug magnet, more than a pencil eraser but it's all fine as it can get. Pinch it and you can't even feel it squishing out of your fingers it's so fine. Is that a sign my reaction carrier assembly with the sun gears/shaft is wearing? I'm going to compare that to the one I just got and see which feels tighter. Everything else I believe I'm swapping out. I'll have to look at the clutches also.
    Tony

    1955 Bel Air Sport Coupe

  3. #13
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    The square ring is what does the primary sealing prevent external leaks. The paper gasket just seals between the passages. The washers prevent leaks past the bolt heads. So they all are necessary. But the usual cause of a leak is the lip seal at the front of the pump that seals the torque converter neck.

    The "fuzz" on the magnet is usually wear from the clutch steels. The wear points on the planetary gears are the brass which won't stick to the magnet.

    Be sure to check thrust clearances as a different case could affect those. Replace the sealing rings on the back of the pump and on the center support. I'd replace all the clutches and measure the clearance on the clutch packs even if it looks like you don't need to. Use your good judgment on the bands.

  4. #14
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    Anyone have the bolt torque specs for the whole trans? I can't believe the thing didn't fall out while driving. The crack goes all the way around and stops at maybe 3 or 4" before the other side.
    Tony

    1955 Bel Air Sport Coupe

  5. #15
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    Trying to make room in my shop for some paying work. With the extra th400 parts left over from the case swap, what should I save and what should I scrap? I'm thinking of saving the governor and cover, speedometer gear, the big clips that hold assemblies in, the clutch steels, speedometer gear housing, all gears, all shims and torrington bearings. The direct drum is the 16 sprag type so that's worthless I guess. The broken case I'll throw out back to see if aluminum scrap spikes, the steel isn't worth my time saving. Anything else worth saving?

  6. #16
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    Case would still work for mock-ups.

  7. #17
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    Quote Originally Posted by markm View Post
    Case would still work for mock-ups.
    Good idea! Although I doubt I'll be building anything. It's cracked so bad it would need to be welded a little just to hang straight. There is only about 3" to go until it becomes 2 pieces. Or I guess for mock ups JB Weld would hold it together? I'll hang on to the truck yoke to go with it for driveshaft measurement.

  8. #18
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    This is old now but I just came across this pic I forgot to post.
    Attached Images Attached Images
    Tony

    1955 Bel Air Sport Coupe

  9. #19
    Registered Member chasracer's Avatar
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    Did you ever figure out what caused the case to crack in the first place?
    Remember the "13"


  10. #20
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    Quote Originally Posted by chasracer View Post
    Did you ever figure out what caused the case to crack in the first place?
    I haven't the slightest clue. There is the old age theory. I believe it led a very long life with many rebuilds. Who knows what it's been through. The BB that came with it was already .030 over so I guessed it's seen a lot of miles. I always used a torque wrench yet I stripped three bolt holes. First one was an upper pump to case bolt which I used JB weld on, drilled straight through the case, tapped it and used a long bolt that came out through the case.

    I don't know if it could have been the problem but the motor for a long time had a little vibration. With this last problem, I ran it without the converter and it still vibrated. Replaced the flex plate and that took care of that. There was also the one mounting part for the dust cover that cracked which I drilled a hole in it and the crack stopped.
    Tony

    1955 Bel Air Sport Coupe

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