70-200 on a T2i

are there any issues with communication between the 70-200 line and a T2i. cause I borrowed my uncles f4 IS and I felt like the auto focus was acting a little weird. any thoughts?

Shouldn't be, define weird.

it was having trouble trying to focus on an object and sometimes I felt like the auto focus didn't move at times. when I asked my uncle if he had any problems with it (he has a 7d) he said no.

Was the focus point very close to you? That is the only time my 2.8 might have an issue. Minimum focus distance is 1-2 meters I think?

Well natively the 7D has a better auto-focus than the T2i. But it still shouldn't be bad at all, unless you're shooting in dim light.

Where you shooting outdoors or indoors? were you on single focus point or?
AI Servo or 1 shot?

Dim light or low contrast. trying to focus on a white wall in full sunlight is also difficult. Though the 7D AF is better, there is no reason a t2i should not be able to focus other than dim light or poor contrast.

Check the focus limiter switch.

Canon11385 wrote in post #15638016
and sometimes I felt like the auto focus didn't move at times.

That statement concernes me a bit as the f4 IS's Af (actually it's not just the AF as it effect MF as well) has been known to crap out.

To test it just turn the focus ring to make sure the lens will go though its full range of focus, from close to infinity and back. Do this with the lens level to the ground, with it angled up, and with it angled down.

If it will not go though the full range of focus and back again then tell your uncle its time to send the lens to a canon service center and the repair will be about $180.

When that happened to my lens, while angled up, it would go from infinity to close but not back and while angled down it would go from close to infinity but not back (or vice versa, don't remember).

May not be the issue but its a simple thing to test and an easy thing to rule out.

Check the minimum focusing distance. There's a switch on the lens. Could be you're just too close to your subject.

I was able to manual focus so we are good there I was about 5 feet away to a lamp.

Canon11385 wrote in post #15640888
I was able to manual focus so we are good there I was about 5 feet away to a lamp.

Minimum focus distance of the 70-200 f/2.8 is right at 5 feet so it's very possible that you were below the minimums. It might have looked ok manually focused but still been a little bit off. Try it again a little farther away.