4L60e What caused this?

[Bigdav160]

I've got a student who lost reverse in his truck. On disassembly, it was obvious it had been flooded. Rust on steel parts and clutch fiber un-bonding from the plates.

I'm glad I made him air check the low reverse piston because it was leaking. Here's the crack in the case we found. Sorry for the fuzzy photo. I've had many hundreds of transmissions apart but this is the first failure of this type I've seen. Funny part is the piston seem to blow out easily on disassembly.

[truckdude239]

Check the teansmisson cooler in the raditor could be leaking pulling coolant in

[clinebarger]

Originally Posted by Bigdav160

I've got a student who lost reverse in his truck. On disassembly, it was obvious it had been flooded. Rust on steel parts and clutch fiber un-bonding from the plates.

I'm glad I made him air check the low reverse piston because it was leaking. Here's the crack in the case we found. Sorry for the fuzzy photo. I've had many hundreds of transmissions apart but this is the first failure of this type I've seen. Funny part is the piston seem to blow out easily on disassembly.

Have you air tested it with the L/R piston, Good used L/R clutches, Center support in place, With the case up-side down with solvent filling the rear of the case to verify it's actually leaking? Could be a casting flaw/Sand cast mark.

[Bigdav160]

New seals on the piston but didn't load any further than that. It took quite a bit of air to make the piston move and it doesn't hold. Air is definitely escaping the crack.

It'll need another case but I'm curious of the cause. The crack encircles the bushing bore approximately 75%

[clinebarger]

Originally Posted by Bigdav160

New seals on the piston but didn't load any further than that. It took quite a bit of air to make the piston move and it doesn't hold. Air is definitely escaping the crack.

It'll need another case but I'm curious of the cause. The crack encircles the bushing bore approximately 75%

I'm curious as well, The first thing that comes to mind is someone got really rough removing the case bushing, But you would think there would be witness marks on the case from using the wrong driver.

Throwing it in park before the truck is stopped? That would make the output carrier try to exit the case

Maybe just a flawed case.

[RANZTRANZ]

when pulling the piston out of the case normally is done with the piston pointing towards the bench so less force would be required to exit the piston out of the case using air into the reverse piston apply hole...also, is that a new case bushing ? But you highlighted that the vehicle LOST reverse, so the issue was there before the bushing was installed....only thinking when bushing was installed...and how it was installed ? pressed in ? correct bushing driver ? I have never seen one cracked there before...the crack looks to me that it was cracked by installing the bushing incorrectly but again you indicated the issue of the vehicle was NO reverse...jury is out on this one....new case for the student...maybe watch how they put in the new bushing next time....LOL.. no need to use press to install the bushing...I think they cracked it when using a press....only way...again, this is only an opinion since I can not see it in person and know all the history...