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So yesterday i was cleaning up the garage, and decided to take all the old oil filters I had laying around to the zone for disposal. It's only 1 mile from the house.... was pretty out... so I took the camaro. Was in no mood for hotrodding and was just driving as if it was my daily, everything was fine till I rounded a corner on the way home. Heard a clunk, almost like a rear end letting go..... then lost most drive pressure in the transmission, drove it home anyway...screw it. Thought at first the torque converter came apart from the noises and just the overall feeling of the car. Dropped the transmission and disassembled it. Pulled the pump.... then the forward drum, problem was clear, as the drive shell..steels and clutches stayed with the intermediate clutch. Knocked the snap ring groove straight out of the drum, it was Game ova. Go figure....
You sir have a terribly unfortunate username with your recent events pertaining to this car lol. Ever get a solid rear in it?
Nah, no rear yet. Car kinda made me mad with this weird/freak failure. Trying to decide between three things here, either put the rear in it and lay down a serious time slip, keep the one that's in it and just cruise around...OR sell it.
4L80 wasn't around in '87 like this 400 of mine. A 30 year old drum is a little more prone to fail after 30 years....along with high line pressure
It may have been fatigue, However...... High/fixed line pressure along with no Wave Plate & excessive forward clutch clearance may have been a contributing factor!
The forward clutch is "static/applied" in all forward gears.... You can take steps to alleviate the shock that the drum/snap ring/pressure plate sees without reducing the holding power of the clutch.
1. Run a Wave Plate....This will cushion the piston apply instead of it slamming into the clutch pack. I have ran up to three wave plates in the forward clutch in fixed line TH400's.
2. The forward frictions only have to "overrun" in reverse, You don't need a ton of clearance here, .035" is plenty unless you drive long distances in reverse, Rev the engine to the moon in Park/Neutral, Or have a "Clean Neutral" set-up.
Excessive clearance allows the piston to gain more speed before it applies the clutch.
3. You can use a earlier TH400 piston & drill a .020"-.040" bleed hole where the bleed checkball "blank" is OR where one of the "casting pour blanks" are if the checkball blank is vented.
Align the wave to where one of the high "crest" is over the bleed hole, As the piston applies the clutch....The wave will flatten out & block the bleed hole.
The bleed hole will lower the apply pressure a little giving a little more cushion & still maintain all the clamping force you had before.....Maybe a little more with the wider work surface of the early piston.
Red Arrow.....Bleed checkball blank
Blue Arrow.....Casting pour blank
It may have been fatigue, However...... High/fixed line pressure along with no Wave Plate & excessive forward clutch clearance may have been a contributing factor!
The forward clutch is "static/applied" in all forward gears.... You can take steps to alleviate the shock that the drum/snap ring/pressure plate sees without reducing the holding power of the clutch.
1. Run a Wave Plate....This will cushion the piston apply instead of it slamming into the clutch pack. I have ran up to three wave plates in the forward clutch in fixed line TH400's.
2. The forward frictions only have to "overrun" in reverse, You don't need a ton of clearance here, .035" is plenty unless you drive long distances in reverse, Rev the engine to the moon in Park/Neutral, Or have a "Clean Neutral" set-up.
Excessive clearance allows the piston to gain more speed before it applies the clutch.
3. You can use a earlier TH400 piston & drill a .020"-.040" bleed hole where the bleed checkball "blank" is OR where one of the "casting pour blanks" are if the checkball blank is vented.
Align the wave to where one of the high "crest" is over the bleed hole, As the piston applies the clutch....The wave will flatten out & block the bleed hole.
The bleed hole will lower the apply pressure a little giving a little more cushion & still maintain all the clamping force you had before.....Maybe a little more with the wider work surface of the early piston.
Red Arrow.....Bleed checkball blank
Blue Arrow.....Casting pour blank
Thanks clinebarger, I agree with everything you said. The reason I was kinda leaning towards fatigue was, it didn't fail as I was shifting from park to drive...or reverse to drive, the crazy thing let go as I was turning a corner at 5mph. And as you said, I do have high line pressure... but with the forward not being a shifting clutch, it was just odd that it let go when it did. Oh well, that's part of the hobby I guess. Oh, and this go around...i will be softening up the forward apply, probably with a wave.
11-28-2017, 03:40 PM
Th400 let go yesterday (surprised at what failed) 
