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55 Tony
08-14-2018, 04:24 PM
I was under the car looking for the source of a new squeak and rattle. Don't know if this was it but I do have a definite problem. The crack goes at least as far as I can see around the converter, further than the picture shows. Could be about ready to fall out? Who was that a month or so ago that said the TH400 bell housings always crack?

55 Tony
08-14-2018, 05:28 PM
I just found one for $150 to pick up tomorrow. I'll probably swap all the parts and be back in business.

markm
08-15-2018, 06:36 AM
No they don't always crack. Ran them in Chevelles and Camaros never an issue, how is yours bolted in.

55 Tony
08-15-2018, 09:53 AM
No they don't always crack. Ran them in Chevelles and Camaros never an issue, how is yours bolted in.

Is there more than one way to bolt them in?

Six bolts to the block and a rear transmission mount.

I've been hammering on it for ... I don't know, maybe 20,000 miles. About 8,000 of that after the performance build. It always shifted really solid with the shift kit.

55 Tony
08-15-2018, 10:25 AM
Came home with a good case and the guy said it worked fine when he drove it home. He bought a rusted out Suburban for the BBC but I don't know what trans he is using. Trying to decide what I want to do, I'm guessing swap the guts from the cracked one to the newer case. I'll look at the clutches but don't expect to see much wear. Is there any parts that get stressed that I should use from the newer one? Or at least check? The old one has the better sprag, I forget if it's 32 element instead of the old 16 one?

markm
08-15-2018, 10:37 AM
The older good cores use more bolts in front pump than later units. What style motor mounts, these things don't just break.

55 Tony
08-15-2018, 12:04 PM
Both are the newer type with less pump bolts. Side mounts from speedway with rubber, tail mount rubber.

chasracer
08-15-2018, 02:49 PM
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.

Rick_L
08-15-2018, 04:43 PM
I wouldn't worry about it since you have side mounts and a crossmember, and the mounts are rubber. Crack may have even been there when you got the trans but too small to see. Most of the cracks I've seen were from loose bolts or forcing the transmission up to the block with the bolts when everything wasn't lined up. But yours is not near the bolt holes.

55 Tony
08-16-2018, 05:20 AM
Maybe the problem was that it's first 12000 miles it was set up with front, mid, and tail mounts? I've heard good and bad about that. Mostly bad. The mounts came as a kit for BB's.

markm
08-16-2018, 06:40 AM
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.

55 Tony
08-16-2018, 08:04 AM
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.

Rick_L
08-16-2018, 07:17 PM
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.

55 Tony
08-17-2018, 02:46 AM
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.

55 Tony
08-28-2018, 12:33 PM
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?

markm
08-29-2018, 10:55 AM
Case would still work for mock-ups.

55 Tony
08-31-2018, 11:39 AM
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.

55 Tony
09-28-2018, 05:12 AM
This is old now but I just came across this pic I forgot to post.

chasracer
09-28-2018, 02:04 PM
Did you ever figure out what caused the case to crack in the first place?

55 Tony
09-28-2018, 03:44 PM
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.

markm
09-29-2018, 06:34 AM
Think of all the hassles you would have saved with a J&W replacement bellhousing.

55 Tony
09-29-2018, 12:34 PM
Think of all the hassles you would have saved with a J&W replacement bellhousing.

That may have been helpful if you posted it in your first reply. I never knew such an item existed.

chasracer
09-29-2018, 03:11 PM
Yes. maybe you're right, the case was just done. We cracked a few Th350 units but that was more due to the car twisting on launch than anything else. Once we got the chassis squared away, it stopped breaking cases.

55 Rescue Dog
09-29-2018, 03:52 PM
A lot of race cars run a mid-plate between the engine and bell housing. I have that setup on my Camaro that really feels like it ties the drivetrain, and car together. The engine is bolted solidly front, and rear in the chassis with the trans attached to it with a poly rear mount.

Rick_L
09-29-2018, 06:13 PM
Solid rear mounts will tear up a transmission case.

Beyond that, most case failures are user induced. Running with loose bolts, tightening the bellhousing to engine bolts when the assembly is in some kind of bind, etc. This one doesn't look quite so obviously that because the crack didn't start or go through a bolt hole. Without an obvious clue, just chalk it up to bad luck, the previous owner, jack rabbit starts, and just hot rodding. It probably won't happen again, at least the same way if you pay attention to the installation.

55 Tony
09-30-2018, 04:30 AM
With the loose converter I doubt I'll have a problem again. It doesn't bang gears like it did, it was shifting really, really hard before and yes I beat the crap out of it.

Rick_L
09-30-2018, 06:23 PM
Just how does a loose converter help? It's the opposite.

55 Tony
10-01-2018, 06:21 AM
Just how does a loose converter help? It's the opposite.
It doesn't have the hard banging into gear when shifting anymore.

markm
10-01-2018, 07:05 AM
That may have been helpful if you posted it in your first reply. I never knew such an item existed.

I never saw the crack before now.

55 Tony
10-02-2018, 12:39 PM
I never saw the crack before now.

There was a pic in the first post. Oh well, besides not being an 8 bolt pump case, it was just shot besides the crack. Three or so stripped holes half ass patched up, one of them being a pump bolt which the new housing bolts to.