4L80E TCU Missing! Will it still move without it?

[MCQaz]

Let me start by saying I am new to the site. Have been searching and browsing for a while but this is my first post.
I recently purchased An M1097A2. It is an Arizona vehicle and appears to be in decent shape. Odometer says low miles (whatever that's worth) With that said it was a non-runner. Based on photos I knew there would be a fair amount of tinkering involved to get it running again. Drained and replaced most of the fluids and all looked to be clean and barely used. I did not drain the transmission. Reason being, the oil cooler was laying in the back of the truck when I got it, and the drain plug was missing in transmission pan. I suspect the transmission is bad and need some advice on testing that theory.
I have cleaned and reconnected the oil cooler and lines, installed new drain plug and added some fresh ATF.
I had some electrical issues on the truck as well. (mostly missing components)
After working my way through that, I was able to verify the engine did in fact run and seems to be in good shape.
However, the transmission does nothing when shifted into any gear.
As I stated in the title, the TCU is missing completely so I am not sure if this could be the reason why. (I would think that I should get some kind of feedback from shifting it into gear though.)
Which brings me to my question,
Will a missing TCU prevent the transmission from shifting into gear?
I have several avenues available for TCU replacements but would prefer to wait until I know if the tranny is any good.
Aso, Assuming the transmission is bad, is it possible to remove it from the truck while leaving the engine in place? Looks to me that it should be easy but not sure if I will run into any clearance issues in the process.
Any thoughts or advice you guys can offer would be greatly appreciated.

 

[NDT]

The 4L80E should still move the truck in second gear even unpowered. Are you sure the transmission has enough fluid and the transfer is in gear?

 

[Mogman]

The 4L80E should still move the truck in second gear even unpowered. Are you sure the transmission has enough fluid and the transfer is in gear?

And reverse.

 

[MCQaz]

The 4L80E should still move the truck in second gear even unpowered. Are you sure the transmission has enough fluid and the transfer is in gear?

It may still be low on fluid, but transfer is definitely in gear.

 

[NDT]

Before you do any more transmission diagnostics, check all your CV shafts for missing bolts or blown CV joints.

 

[MCQaz]

Before you do any more transmission diagnostics, check all your CV shafts for missing bolts or blown CV joints.

Um, thanks?
I have checked that already. Found a couple of missing u-joint clamps but have replaced them already. Did this before I got the engine to start
Not sure if you were inferring that this may be my problem or not. (no connection to wheels) So I'm trying not to be insulted.

 

[NDT]

Um, thanks?
I have checked that already. Found a couple of missing u-joint clamps but have replaced them already. Did this before I got the engine to start
Not sure if you were inferring that this may be my problem or not. (no connection to wheels) So I'm trying not to be insulted.

Folks come on here all the time with the issue of “my HMMWV won’t move” and more often than not, it’s CV shaft related. Didn’t know you already checked those.

 

[Mogman]

Belated WELCOME to the SS forums.

 

[TOBASH]

Um, thanks?
I have checked that already. Found a couple of missing u-joint clamps but have replaced them already. Did this before I got the engine to start
Not sure if you were inferring that this may be my problem or not. (no connection to wheels) So I'm trying not to be insulted.

No way anyone was trying to insult you... These rigs are typically missing parts and have loosened parts, so seems to me that you were being reminded to do your due diligence.

IMHO.

Belated WELCOME!

 

[williamh]

Right ! It may have been parted out before it go to govplnt so making sure it’s not missing (any) assorted bolts or shafts that would keep it from moving is what we’re trying to say. You never know what was pulled off. Like the bolts to the tork converter.

 

[MCQaz]

Folks come on here all the time with the issue of “my HMMWV won’t move” and more often than not, it’s CV shaft related. Didn’t know you already checked those.

I do not doubt that at all. I apologize for being so thin skinned.
I do trouble shooting for a living and I suppose I would do the same thing.
You have to start with the most obvious to check them off the list.

 

[Mogman]

Make sure the trans fluid is full after running it, over time the torque converter and trans cooler will drain out of the open plug and even if you fill it static it will likely pull all the fluid out of the pan as soon as you start it.
Good luck with your new truck!!!

 

[MCQaz]

Status Update
I got the old girl to move!
It seems it was just too low on fluid. I put nearly 1.5 gallons of fluid in it before my first post. I know it takes more but i did not know how much was left in the system and the tranny cooler is bypassed. Put all that I had in it and was expecting some response considering how much I put in.
Went out yesterday and added another couple of quarts. That did the trick!
It moves forward and reverse! Looks like I will get that TCU and see what I have.
I appreciate all the help.

 

[MCQaz]

Right ! It may have been parted out before it go to govplnt so making sure it’s not missing (any) assorted bolts or shafts that would keep it from moving is what we’re trying to say. You never know what was pulled off. Like the bolts to the tork converter.

The truck sat in my driveway for nearly a week while I was waiting for the batteries. During that time, I spent countless hours on my creeper inspecting it with fine toothed comb. I found numerous loose bolts, wire connections and plugs. I have a long list of things that need to be corrected or replaced already. Seems like every time I check one item of the list, I add two more!
That is part all the fun though I guess!