fire67bird

My wife's 2007 Tahoe was slipping in 2nd and 4th gear, worse in 2nd though. It has 190k miles on it so I decided it was time for a rebuild. I suspected that the 2-4 band was wore completely out and when I pulled it out, the band was broken in half about an inch from the apply pin.

I'm glad to have found my problem but want to make sure that there isn't another factor at play other than fatigue.

What else other than verifying that the piston applies should I be checking for to make sure that something else didn't cause this problem.

coryforsenate

iTrader: (1)

I'd wonder why the band broke in the first place.

Have you checked line pressure?

Was it acting weird before it started slipping, like harsh shifts?


Edit: nevermind, I reread and you have the tranny out and obviously can't check line pressure

fire67bird

I think you may be onto something with the line pressure.

During reassembly I did notice that the 3-4 accumulator check ball capsule was not sealing properly. I had to take compressed air and blow it out real good to get it to seal. I wonder if the leaking check ball could have caused the computer to command high line pressure resulting in the broken band.

It's my wife's vehicle so I don't know if it was shifting hard before the slipping started. She just drives until the problem can no longer be ignored. ha

mrvedit

Perhaps some of the pro mechanics can chime in about how common/rare a broken band is, but broken bands have been reported here.
I would replace it with a quality band and not worry too much about why this one broke.

clinebarger

Probably just fatigue, Right above the apply bracket is where the band flexes. GM uses the "2-Ring" apply pin on just about every 4L60E, And most have loose (out of spec)Band clearance from the factory, Though they want field techs to check & correct Band clearance.

High line pressure & Harsh 2nd shifts usually rips the bracket off &/or elongates the Anchor Pin slot...eventually pulling through.

Watch your band clearance upon assembly, Probably need a band shim (Trans-Go) or a longer apply pin (Sonnax-"preferred fix").

You want somewhere between .065"-.100", The Sonnax pin will allow customizing Band clearance.

A OEM Borg Warner High Energy band will be fine!

PBA

Go with the Borg Warner Hi-Energy 2-4 band (oem), and set the band clearance to the minimum .065". Add the Corvette servo and set the 3-4 clutch clearance at .020" - .035". Almost always the drum will be dished in the middle where the band rides, and needs to be replaced. Replace the reverse/input drum with a oem version.