My95Z

iTrader: (8)

I'm totally lost now. Replaced all the clutches and seals in my 4l60e and several weeks later the same thing happened to why I took it apart in the first place...3-4 failure.

So clearly their is a reason the 3-4 is failing, new seal so doubt that would be it, but I'm thinking pump or other problem causing low line pressure.

Any suggestions welcome/appreciated, thanks.

performabuilt

iTrader: (25)

Line presure test would be in order. But you also need to inspect the inside of pump stator. teflon rings on the input shaft.Did you replace the oring in center of input drum?

My95Z

iTrader: (8)

Little late for a line pressure test, already tore it from the car. It just didn't make sense, ran great/shifted fine all the time till I heard it bounce off the limiter once then it was done.

I'm pretty sure I replaced the O-ring, and will see if I can find any ripped seals or such when I take it apart. Only other thing I knowticed was the trans was extremely hot when I was taking it out, even after an hour of cooling.

My95Z

iTrader: (8)

Well I got it all apart now, goes much faster the second time lol.

Everything looks fine except the 3-4 friction materials, they are toast. The pump also looks good, so I'm thinking overall pressure wouldn't cause only wear on the 3-4 so I'm thinking it has to be specific to just the 3-4 not just the whole trans right?

transamsixspeed

iTrader: (2)

you really nned to check the inside of the pump stator where the input shaft rides. there are 4 white teflon rings that seal inside the stator. bushing failure is common inside that stator letting the sealing rings to tear grooves inside the stator tube run your finger inside that stator tube from the inout drum side and see if you feel any grooves. if it isnt completely smooth then the stator and input shaft will need replacing. Also there is a abuse plug in the valve body that wears out and cause premature 3-4 clutch failure. How does the band look? How about the accumulator piston that is in the case?

My95Z

iTrader: (8)

The 2-4 band looked fine, but I think I may have found the problem.

Could this have caused it? Cracked piston.

PedaltoMetal

^^ well there's your problem. You don't have any seals on the piston. Nah j/k.
That's the forward piston and is applied through all forward gears. A crack like that is not what caused the frictions to toast as the 3/4 piston is below it. Check on what Frank suggested. The o-ring is very tiny and thin compared to the others so it's easy to overlook.

My95Z

iTrader: (8)

So you don't think the cracked piston is the cause of the problem? The crack is all the way through, so I just guessed that was it.

Is the O-ring in the picture you posted or do you mean the little one on the front of the imput shaft?

PedaltoMetal

The crack is a problem but I don't believe it caused your toasty frictions. But anything is possible. The o-ring is not in the pic, just pointing out the grove where it goes. I almost forgot this when I was building. The little seal on the front of the input shaft is the lock-up seal. Bought the diameter of a nickel.

My95Z

iTrader: (8)

Oh, I see the red marks now, thanks man. The thing is I didn't even go down that far originally so the o-ring was still in there and good. I pulled the 3-4 apply and it looks in really good shape also, so now I'm even more confused.

Thanks for sticking with me guys, I'm really trying to learn.

PedaltoMetal

What do you mean by 3/4 apply? Molded piston shaped like a cone or the "5" fingers?

My95Z

iTrader: (8)

Molded piston shaped like a cone, but both looked good (sorry about the terminology lol).

Papermachtech

This can be a pita. Be sure the bushing is new and the input shaft that rides in the bushing is just as new. NO room for error here. The bores of the accumulators wear. Replace them preferably with the pin less style. I like to use the "D" rings on the servo this also helps. Check your pressures and keep the transmission to the top of the add mark on the dip stick. The extra heavy duty clutch pack would also be an improvement. Leave the return springs out.