SOOOooo... ALL aftermarket RADIATORS are the auto-trans version, zero M/T specific models?

[lil_Blue_Ford]

IF I'm following you, this extra "reservoir" (which should just be filled w/ dead-air on a 5-spd) suffered a cross-over LEAK from the main coolant-filled part of the radiator, and if your truck had been equipped with auto trans, said trans would now be contaminated with anti-freeze and water, "milkshaked" in with the ATFluid???

It *can* happen, but usually it leaks around the bulkhead fitting or along the tank seams where coolant just leaks outside

 

[RobWigglezz]

It *can* happen, but usually it leaks around the bulkhead fitting or along the tank seams where coolant just leaks outside

The only way coolant could leak into the trans reservoir is if the the O-ring face bottoms out before the pipe thread gets tight. I wouldn't doubt a cheap aftermarket radiator would tap the pipe thread too deep and not seal as the O-ring face gets tight.