bgreen

Background
My dad's 1971 Nova project, found a junkyard 2004 6.0L LQ4 & 4L80E to swap in.
The engine and transmission are from a 2004 Express van, but the harness was damaged from that vehicle, so we found an harness from LQ4 4L80E Silverado that was intact.
Installed new stall converter, no transmission work otherwise.

Did some engine related work (DIY head porting, cam, headers), got everything running a few weeks back. Got the initial leaks/issues sorted out, put car on jackstands to check transmission operation.

Reverse works fine, but there are no forward gears. When it is in any forward gear, engine revs like it's in neutral.

Other details:
-Rewired the harness ourselves (remove DBW, match the cartridge MAF, remove emissions and unused stuff)
-Computer was reprogrammed at Speed Inc for a startup tune, with our combo of injectors/MAF/cam/transmission/gearing etc.
-The harness to PRND indicator plugs were different; rewired those, and on EFI Live the selected gear shows correctly.
-Gone over the transmission wiring a dozen times, it seems to be correct, but anything is possible
-Transmission fluid levels look good after several sessions idling and warming up
-Transmission fluid in cooler lines seems to flow
-No DTC's displayed in EFI Live
-Transmission gives no physical indication/clunk that it tries to shift gears
-Reputable vendor who sold engine/trans noted that the vehicle drove fine when they took it in, under 70k miles

What would be the next steps in diagnosing this?
Does it seem like it could be electrical, or more along the lines of hard parts?
I've read that we should be able to have reverse without any electronics plugged in. Is this correct, and can a similar test be done for any forward gears?

Thanks for any input.

mrvedit

If you unplug the trans harness, it will be in limp mode, which is 2nd gear for a 4L80E. You will also have Reverse.
It does not sound electrical to me, but try disconnecting the trans to be sure.

clinebarger

The trans Dipstick & Tube are not from the Van....So what are you using? If its not a fluid level issue, Or shifter adjustment, Time to pull it & look for damage. In particular the Forward Clutches.

bgreen

Lokar. I forget what my dad did, but adjusted it such that fluid level should be reading accurate (fluid level at/just above the pan level IIRC).

bgreen

Disconnected round plug, no change in behavior at all.

What are the next steps, or likely culprits?

Fluid level should be fine, 12+ qts of non-synth ATF were used, and fluid level still seems fine. It is cold here, but the garage is heated to somewhat comfortable levels.

clinebarger

Time to pull it & tear it down, If you need any info on tear down let me know.

bgreen

Any suggestions on tools/tutorials/manuals on tear down are appreciated.

I'd like to tackle it ourselves, maybe do some upgrades while we're in there.

clinebarger

Anytime I go into a unit I'm not familiar with....I buy a ATSG manual, It will cover the Basics, I still have my original '91 version.....LOL.

You being in the rust belt....You may need a Pump Puller, Corrosion builds up between the Pump Body & Case, You can get inventive if you want.

Torx socket for the 4th Clutch housing Bolt (forget the actual size), 3/8" 12-piont socket for the Center support Bolt.

Clutch return spring compressor, K-D makes a fairly cheap one that works good. Well it now cost $100......I bought mine for 1/2 that several years ago....
Snap/Lock ring pliers, This is what I use....https://store.snapon.com/Snap-Ring-P...e-P647704.aspx Just an example....I wouldn't pay for premium tools for a 1 time deal.

Convertible Snap ring plier set....For the Boost Valve, The Snap Ring that retains the seal behind the Case Bushing, And the Snap Ring that retains the Input shaft to the O/D Planetary.

A pocket/Mini flat blade screwdriver works really good for clutch pack snap rings.

A few pointers.....
Remove the Valve body & the 4th Clutch housing bolt & the Center Support bolt.
Remove the Rear Band Servo/1-2 accumulator assembly.
Remove the rear Cooler Line fitting.
Do these before pulling the guts out of the Case!

Use 2 long Hooked Awls to grab the Direct Drum spring cage & pull the Direct Drum out.



If you find the Forward Clutches burnt, Check the Bushing in the Forward Drum for damage & where the Sealing rings ride, This is a high wear area.....

Picture of the Input Shaft wearing into the Forward Drum....The two lands should be smooth, If damage is found here....Replace the Forward Drum! Along with the Stator Bushings


Flip the Forward Drum over & check the Bushing, (If the Sealing ring area is OK, Or you buy a used Drum), I replace this Bushing 100%!



If the Forward Drum bushing gets worn enough & the Input Shaft digs into the Forward drum enough.....The Input Shaft can get damaged....Inspect it really well.