Chevy k10 problem

[86lover]

1986 chevy k10 350 small block 4x4, when i put the truck in park it runs great...but when i put the truck in over drive, drive, 2,1 reverse it has a problem and bogs down really bad and is struggling at this time i throw it in park and its fine, this all happened when i was driving with a full load of medal and stop d at a light and when i took off it started doing this and hasn't been the same
just had a tune up not long ago

 

[Jims86]

1986 chevy k10 350 small block 4x4, when i put the truck in park it runs great...but when i put the truck in over drive, drive, 2,1 reverse it has a problem and bogs down really bad and is struggling at this time i throw it in park and its fine, this all happened when i was driving with a full load of medal and stop d at a light and when i took off it started doing this and hasn't been the same
just had a tune up not long ago

Has the truck been modified at all? Could you post a video of what is going on...maybe to see how bad it bogs?
Does it try to jolt forward real bad when you put it in drive?

 

[77jimmy]

Check the all vacuum lines.