Originally Posted by budhayes3

What year is the 2500? If it's a 99-00 he will need to buy a crank spacer to bolt up to the 4L80E, as those years had a longer crank and did not use the spacer that the later years do. It will run on the 6.0 tune, but I wouldn't leave it like that permanently, so factor in the price of a tune to the swap.

Originally Posted by moes04silverado

Correction! If its NOT a 99-00 you will need the .400" crank spacer. The 99-00 crank was already longer. Trust me, Ive been fighting this situation for a few months try to get a 99-00 6L bolted to a 4l60e! I got it resolved...

Originally Posted by nickleahy23

I have a 2001 6.0 on a 4l60e n I didn't need a spacer..the 99-00 you need one for the 4l60e