Recently finished rebuilding a 4l80e that I picked up. Came out of a 99 k2500. I did the direct fed and basic rebuild, new seals, pistons, clutches, steels, bands. Got it put together and found it has no reverse. I haven't driven it, but it pulls itself forwards no problem in 1st gear, got up to 10mph. When shifter is in reverse it acts like its in neutral, dont hear or feel it engage. Fluid is filled up, Pressures seem good, 75psi at idle, hits 300 psi in reverse.

I pulled the servo pin to check the length, but wanted to see if anyone thinks it could be something else? I can't tell if it's engaging the band or not.

 

Do you have 3rd gear (direct clutch)?

Do you have engine braking in manual 1st (low/reverse band)?

These are the two elements that are on to give your reverse...

 

There's another...

 

The Direct Clutches also need to apply along with the Rear Band too obtain reverse, The Rear Band is usually the last place of interest if the unit was assembled correctly, You can reuse the Rear Band 99% of the time & The Servo has 2 miles of travel.

Was the Reaction Carrier "Band Surface" in good shape? Was there any burnt clutches/band when you tore the unit down? Did you air check the Rear "Lo/Reverse" Band & Direct Clutches upon assembly?

 

Are you counting the OD roller clutch holding?

 

Yes.
Good chance thats the problem in a fresh novice rebuild.

 

I see your point, but he wouldn't have any forward gears, though, if the OD roller was wrong.

 

I guess he would if the overrun was on...

 

He will if he manually shifts or at least puts it in 3rd..
I've seen it a time or two.

 

I see where you're going. True story... That would indeed bring the overrun on.

 

I'll take it for a drive tonight and see what it does. If I put it in drive it goes forwards fine. If it's the OD roller what other symptoms would it be ?
I snapped a few pics of the servo pin, looks like it took some damage. It was stuck in the piston.




Old servo





Left is stock, right is a spare i have

 

If it pulls with the shifter in D4 (OD), The OD roller clutch is holding, If you have to pull it down into D3 (D) to get it to move....The roller clutch is not holding.

Was the servo pin you swapped in shorter than the original?

 

Good to know the roller clutch is ok. So I used a telescoping camera and looked inside where the servo pin goes, and found the band had fallen down further into the case. So I got the tranny pulled and torn down again, and the band was sitting below the pins. The pins look fine, just looks like the band came off them possibly when I was installing the front assembly.

Any tricks on keeping the band in place while installing the front assembly ? I'm thinking put the band in and put the servo pin in to help hold it in place.
Also, the new band has lines on the part that meets the drum, the old band was completely smooth. The drum feels smooth but you can see lines on it, matching the new band.




Picture i found showing the 2 bands. New band is like the left one, old band is right one.

 

Get the band seated on the 2 Case Lugs, That's what I do, Never had a issue with the band falling down, However you can install the Band Servo/2nd Accumulator assembly & do a air test before you install the Center Support.

Air test here.

 

I'll do an air test to make sure it's good. Ill make sure it's seated good this time around, I thought last time I had it seated but clearly I didn't.

 

On a side note. I want to make sure I installed the pump gear correctly, does anyone have a picture of which way the gear goes? Which way should the dots go ?

 

The dots face away from the pump bushing, When you install the gears in the pump body, The dots face up, The drive "flats" get offset to the rear of the trans.

 

This is how I always do it, too. In the hundreds of 4L80E's I've done over the years, I've never had a problem.

The band is basically the first thing that goes into the case. I work it down into position, and then take a long screwdriver and reach up through the rear servo pin hole in the case and press on the end of the band (where the pin engages it). This will pop it into place on the two case lugs. Once it's there, it won't go anywhere. Drop the gear train and center support into place (don't forget the fret snap ring under the center support!).

I generally use Borg Warner bands. Usually the new bands have the smooth lining...

 

Thanks for the info. I tried to get the band that came with the rebuild kit to seat, but it just wouldn't go on the case lugs. So I put a new BW band and no problem getting it to seat, it's also a smooth liner vs the other one. I assembled up to the center support and tested the band with servo pin. WorkeD fine, could feel it engage the band then when you let off you could feel the band push the pin out.
I'm going to double check the pump gear before assembling. I believe I installed it the way it came out but want to make sure. I had converter clearance issues with a remaned converter, just needed to shim with 1 washer.

 

So I got it all back together, now it goes forwards in every gear, even park. WTH is going on, all I did was switch the reverse band and used the longer servo pin. Could the pin to too long that it is causing the forward in all gears condition ?

Edit - I shut it off once it was going forwards in reverse so hoping it did no damage to the clutches. Fluid did not smell burnt or anything, still nice and red as well.