How does trans die?

caddy radiator leaked coolant into trans fluid. turned trans internals/friction discs too mush. motor drives torque convertor which has a viscous clutch but that fluid which is silicone, does not mix with trans fluid. i loosened radiator outlet line and tried to let motor pump out old fluid but nothing came out. i assumed torque convertor was probably ok but the new/used trans came with a convertor so i used it. what part or section of trans actually generates fluid pressure? i know i had major slippage due to destroyed clutch discs but what other major issues did i have with internals of trans?

The torque convertor uses transmission fluid supplied from the transmission reservoir. The fan clutch is silicone fluid, not the torque convertor. You can’t get all the trans fluid out of the torque convertor unless you drill a hole to drain and then plug it.

The fluid pressure come from an internal oil pump usually mounted behind between the torque convertor and inside the transmission itself. The pump is used to shift, cool, and lubricate the internal tans parts.

The introduction of coolant (50% water) into your tranny will have as many bad effects as water in your engine oil. Bad for bearings, bad for clutches, bad for valves, bad for corrosion. Just plain bad.

A few ounces of water will trash a transmission in a few short miles.

“how does trans die?”

It starts slipping for whatever reason. The slipping quickly destroys whatever clutch or band is slipping and the transmission will no longer go into gear…The car becomes immobilized…

‘how does a trans die?’

As Caddyman replied a friction element starts slipping which causes the oil to overheat. The overheated oil loses its viscosity and the line pump cannot build pressure allowing worse slipping until the pump no longer can build pressure at all. The heat of slippage warps the friction plates, causes the friction material to lose integrity and shed, and hardens, cracks, and destroys the piston seals further compromising the clutch fromworking corrctly.

When the oil cools you might be able to drive the car or truck until the slipping element is reengaged at which time the vicious circle starts again. If the transmission holds together long enough, the oil can catch fire and start an engine fire.

Automatic transmissions are hydraulically operated machines. The transmission fluid is a lubricant, a coolant, and most importantly the medium that applies the hydraulic pressure generated by the transmission’s pump. The pump is driven (usually) by the torque convertor, which means it’s indirectly connected to the engine’s crankshaft. If the engine is running, the pump should be developing pressure. The reason most transmissions fail is because of a loss of hydraulic pressure, for whatever reason.

What usually happens is one or more seals inside the transmission wears, or more commonly, gets hard, and loses its ability to seal. It usually starts slowly, so that shifts start to overrun, or it takes a moment or two to go into gear when you put the selector in “Drive”, etc. Seals can also be damaged/torn because of a lack of lubrication, or by simply overheating.

Once a seal fails, hydraulic pressure is lost, which means the transmission can’t effectively apply its friction elements (clutches or bands), and they slip. Automatic transmission clutches and bands are designed not to slip at all, and as a result they can’t tolerate slippage. Driving a slipping automatic for a single mile is enough to permanently ruin it.

Simply stated…oil and water do not mix. Especially in a transmission.

I watched a few videos of trans tear down. U remove side cover and there is a pump assy and valve body assy that comes off. Typical fwd GM trans layout. Than the disc/drum section is torn down. Lots of parts

One user said that when the transmission dies, the car will be immobilized. If you’re going in the highway at 70mph and trans dies, what does this mean? Does it lockup? what happens then? what should you do?

Transmissions rarely lock up when they die. They usually simply lose the ability to transmit power in one or more gear. That means that they can’t drive the car, so you coast to a stop. Or never get going in the first place. Or get going, but then it shifts to a gear that has failed and the clutches slip so you slow down again, Or Reverse doesn’t work.

The possibilities are endless, but generally, locking up is not going to happen.