So regular driving on the street seems normal so I would think the transmission slipping wouldn't be the diagnosis, but not sure.

Here is the back story. Wen't to pismo beach and went to pull a van towing a small tent trailer into the softer sand, I was in 4 Hi and once the strap was tight and i got on it, it didn't even try. I mean it revved up normally but none of my tires spun. I have the Detroit TruTrac in the rear so even if It was too heavy to pull out I should have dug two holes 50/50 in the rear and one up front. But i got nothing, like i said it was if i just put it in neutral and gave it gas. Could by Torque Converter not be going into full lockup?

It drives ok on the street but it does feel like a dog, which I don't think it did in years past. Maybe a slow decline hid the problem from me until it got to a specific point?

 

Torque converter won't lock up until you hit third gear, and certainly not under high engine load. (such as you would be experiencing there....) your trans was slipping.

 

Ok, yeah I need to take a course on TC's.

But if the trans slips in the scenario, would it make sense that it would always be slipping to an extent? Possibly why it feels sluggish?

 

You could try changing the fluid and filter with a band adjustment. Might help for a while, but chances are, you'll need a rebuild soon.

 

I just did fluid and filter and bands about 20k miles ago. Would a Mega Viper be over kill? I just want to replace the trans and TC once and be done with it. I always read guys that do Re-mans run into problems not even 10k later. I won't be getting a new truck anytime soon, plan to keep this for another 10 years or more.

 

Most certainly. I am a big fan of overkill.

 

if you go the mega viper route be sure to post pics of your install!!!