vby4733

1st time poster, been lurking for awhile. I have a 4l80e no reverse. suspected rear band because of no engine braking in 1st manual. so tore it apart til i got the reverse servo out. now dumb question, I can use a screwdriver and push the reverse band or where the pin contacted all the up no pressure. the same spot also is loose, wiggles and moves around by my touching it with a screwdrivers . so the reverse band is broken right?? thanks for any help

Jays_SSZ28

iTrader: (2)

Band isn't a problem. The pin is too short. Very common. Can get a longer pin or weld/grind the pin you have.

Check the piston very close for cracks, usually when the pin is too short the piston bottoms out, slams the case and breaks. Or just hairline cracks around the OD on the case side.

Jays_SSZ28

iTrader: (2)

You can put the servo back on and apply it with compressed air. A hard bang is the piston bottoming out. Should sound like a dull thud.

vby4733

but it definitely feels like the piece where the pin contacts the band is broken. that part of the band shouldn't move by me just barely touching it?

Jays_SSZ28

iTrader: (2)

Can you push it all the way up? Trust me, the band is not broken. It's very common for the pin to end up short.

vby4733

yes I can push it all the way up with no pressure at all

Jays_SSZ28

iTrader: (2)

If you're certain the problem is the band then pull the transmission out and look.

The first 4L80E I worked on I still own. It had 60,000 miles when I got it and no reverse. I took the whole thing apart and replaced the band (nothing wrong with it) it had reverse for a while and lost it again. I even welded the pin tip up and it worked a while again and stopped.

Last time I did that I welded it up to where it was on the tight side and it's worked fine since. Through all that at some point it broke the piston when it bottomed out in the case.

The problem as I remember is the change in friction material from the old th400 band (thick friction material) to the thin material. And they came out set on the loose side.

Now if I build a 4L80E I always set the band up on the tighter side and never had problems.

On the other hand these do have problems with high pressure breaking parts. I've seen the direct drum blown apart from this but never a broken band, I have heard of bands breaking but it's rare.

So if you do get it apart use Sonnax or TransGo parts to prevent future high pressure problems.

And you might as well plan on a rebuild, no sense in getting into it and not replacing bushings and other things. In fact my 60k trans had bad bushing wear too, thats all I changed was the bushings and band. Been 15 years in a 454 dually that I use for towing, still works great.

vby4733

yeah ill probably be going for a minimal rebuild with bushing and band like you did. along with the better sonnax and probably stuff from the transgo kit

vby4733

ok so another question, finally got tranny out and apart. the reverse band is broke where pin contacts the tab. now it is a 95 early 4l80e with a grooved reverse band. I've been looking for another grooved band and came across information that all they make is smooth now. so I need to replace the carrier to the late model now to use with the smooth band? is this correct? or is there really any harm in using a smooth band to replace a grooved band?

MaroonMonsterLS1

Does the drum have grooves worn in it?

vby4733

it has some grooves in it but they don't seem to be too severe

MaroonMonsterLS1

If you can catch your nail on them at all, I would either use a grooved band again, resurface the drum, or just get a new drum.

Plenty of places reline grooved bands. Any WIT supplier should have a bunch in stock. 34024 part number.

vby4733

thanks for the help! so the kevlar relined ones for a 400 will work just fine then?