I have a 99 ram 2500 4x4 v10, will the front and rear differentials from a 2001 ram 3500 cummins bolt up to my 2500 without any issues??

 

It should.... I think they are all the same as long as you have the same differentials. Even if there is a difference, I think they will still interchange pretty easily. Just dont forget since you have the 4X4, that what you change on the back must be changed on the front, if you are changing gear ratios.

 

Im talking about the whole differentials, can I take them out of a 3500 and bolt them up to my 2500?

 

You should be able to do that just fine.
I think...

 

bolting up will be fine, just double check the brakes are compatible with your master cylinder/ABS, also check the driveshafts, they may be different yokes... the front will be a D60 and i think both the v10 and cummins have a d70 rear, so they should be the same.

 

Except for 1994-1995 2500s, I believe all 2500s and 3500s had the same D60 front axle.

However, the rears are different.

1994-1995 2500 w/ V8: Chrysler 9.25 (same as 1500)
1996-2001 2500 w/ V8: D60
1994-2001 2500 w/ diesel or V10 and auto tranny: D70
1994-2001 2500 w/ diesel or V10 and manual tranny: D80
1994-2001 3500: D80

Source: http://dodgeram.org/tech/specs/Ramspecs.htm

 

i thought all d80s were duallys.... i guess i thought wrong. anyway. they will still bolt up, just check the brakes and driveshafts.