Technical BOP TH350 resistance in park

Hi all, I’m new here. I have a Pontiac 455 with a th350. I have been rebuilding the car I put all new seal and filters inn the trans mission. I was operating as it should have. It’s only been driven around my yard a few time no more than 15 -20 mph to ensure shifting after install. I go and crank it about 2 times a week it’s not streetable yet. Today I crank the car up and with the trans in park it acted like the emergency brakes were on not letting my engine rev freely. It got hot fast and started to smell I shut it down after about 5 min. It was low on fluid when I checked it so I went and got mercon II fluid and topped it off about 2.5 low. I crank the car up and it still does the same thing. I don’t know what happen from a week ago till now but it’s holding my engine back from reving freely and it seems like I have no pressure in the cooling lines. Anyone know what could be going on or is it time to rebuild

 

I had a C4 years ago that acted like that. I bought an engine with the C4 attached that had been sitting for a year or so. I asked a friend who was a transmission man what was going on and he said I had a stuck torque converter from sitting. I drove it for a while like that and all of a sudden it let loose and started to work correctly and never had any more issues.

 

Sounds converter related to me as well.

 

Does it rev ok in neutral? Might want to try unbolting the converter and sliding it back.

 

Is it a later 350 with a lockup converter? Sounds like one trying to lock.

 

When you say all new seals I assume you mean external seals. Pump,tail housing etc correct? Did you have converter clearance when you put it in? Super critical!