oil cooler thread size

[JurgenS]

I have a 2006 Silverado 34" radiator (on an '89 c1500 with a 4l60e) and I'm installing a B&M auxiliary oil cooler. I"m looking for the thread size in the radiator. Almost everywhere I find it should be 3/8" but that's way too small. Measured with a vernier it is much closer to 5/8" or could it be metric 14mm?

Same goes for the transmission but there the information I found is mostly the same, it should be 1/4" NPS (straight, not NPT)

I don"t have either connector so I cannot test fit. Can anyone confirm the correct sizes before I order connectors?

 

[98_k1500]

I know the ones in the trans are not tapered. Im really not sure about the radiator.

 

[JurgenS]

The ones in the radiator aren't tapered either.

 

[98_k1500]

That seems right, I think they are 3/8 up there. The engine oil cooler is much larger.