How do I tell if the truck I bought is a 100 or a 150?
Is there any real difference?

 

Both are 1/2 ton.
I believe the 150 has a higher load rating due slightly heavier duty suspension.
If I remember correctly it was introduced as a heavy 1/2 ton.

 

I did not know that they had a D150. Iknow they have a W150, which is a 4x4.

 

Any W is 4x4, be it 100, 150, 250, 350 or whatever.
All 4x2 were D series.

 

D100/150 2wd
W-series 4wd

EDIT: Had it wrong!

 

What about transmission and gearing. Wouldn't a higher load rated truck need a heavier power-train?

 

All d trucks are 2wd and w trucks are 4wd. If a auto it is a 727 and a stick i think is a 904 trans not sure on the gearing

 

The 904 is automatic, not as heavy duty as the 727.

 

My "D" has overload springs on the rear. Also the "150" on the fender. I believe that's the only difference.
Slant6, A833OD trans.

 

pre-1981 it's a D-100, 1981 and newer are D-150, 1994 and newer are 1500.
(I think it was 1981)
Other than that, from what *I* have seen, they are pretty much the same truck. Pretty much just updating it with the times, like they did in 94 for the 1500 tag.