I've been researching my trucks transmission and possibilities as to why it isn't driving right for a little over two weeks now. Think I posted MANY months ago about my flashing od light, but power loss was so random I just became use to driving it (occasionally) without od.
Fast forward a little over two weeks ago.
Truck starts having trouble shifting from 1st to 2nd and after it warms up, rpms peek at 2500, pull over turn the truck off and on again put it in drive and down the highway like nothing ever happened. Trans fluid was almost 2 quarts low, fill it up. Pull the vss clean it and it's connections.
I get a whole day where I'm confident that fixed my problems, it's driving noticibly better. On my way to work cruising about 55 I loose power and rpms are maxing out at 2500 again only this time when I pull off the road truck dies. It starts after more effort than usual. Now there's a shudder, but I shifting and no more blinking od light. I get the front end in the air because at this point everything I've researched points to a clogged trans filter. Pop the hood and I noticed the positive posts connections on the passenger battery are just UGLY in pretty much every way imaginable. I clean it up, tighten and replace what I'm convinced came from the factory. And go for a drive ........ Everythings doing what it should and no shudder. Been like that for three days fingers crossed. What I wanna know in the mean time.

Is it possible that a mixture of low voltage and a partially clogged trans filter can have such a serious seeming impact?

Local diesel shop said transmission needed to be replaced!!! Almost made my wife cry
Also, I don't think my 4x4 truck has a 4x4 trans pan.....

 

I’d say Absolutely. Poor battery voltage will MESS YOU UP. IMO it’s more so on diesels especially. My 6.4 alternator went out and I lost all my voltage on the interstate and it went nuts!! Barely got it limped to a gas station and had to get a ride to oriellys for a new one. Fun times. Anyway yes there’s no telling how poor battery connections will affect your truck

 

Also just make sure you keep the trans fluid up. Since you have a leak you know to watch it now

 

About 2 months after I got my BTS trans, my OD light intermittently gave the blinks and sent the trans into limp mode. Brian suggested that I readout the signal from the VSS on autoengineuity, because if the alternator doesn't put out a "steady" 12V, it can mess up the VSS signal that the PCM sees, which sends the trans into limp mode. I ended up replacing the alternator, and that solved my issue. It sounds like your issue could have been similar.