Well, sort of the wrong thread here as I have an H3T, but the H3 category has a lager community that could have the same issues. So....
I have the GM Roof Rack Cross Bars for my H3T and though they have a lever to "lock" them into place, I can still easily slide them back and forth. Anyone else have this issue or come up with a solution?

 

Well, on places where it won't be seen, I tend to fix fitment or clearance issues with a piece of canvas or rubber.

For example one of the plastic inserts on the body for my tail lights to snap into was super loose and would come out with the tail light, also causing it to not sit right against the body.

I wrapped a piece of canvas around it, tapped it back into the hole with a rubber mallet, and called it a day. No more problems with it coming loose or coming out.

I've not ever handled the roof racks directly but maybe you could wrap a small piece of canvas or cloth around whatever surface is contacting the inside of the roof rails to tighten up the clearance a little.

 

I not saying this is your trouble but mine also moved and after awhile of scratching my head even though I was sure they were all the way in the locking channel they were not had to apply a lot of down pressure now all is good!

 

My lock levers seem to act differently in reference to where the crossbars are placed in the tracks. Sometime they will lock easily and other times I think they are going to snap before they lock. Try different locations along the tracks and see if that works.

 

There are not 'infinite' adjustments. There are a number of notches in the tracks that the locking lever will allow you to locate the cross bar. When you feel it lock easily, you're in a notch.....when you think they're going to snap, you're in between notches. You have to wiggle the cross bar forward and rearward a little as you lock the lever. You'll get a feel for it. It would have been nice to have molded in markers in the roof trim to show exactly where the notches are, like the H2's have.

 

Mine definitely does not appear to have any notches. Even while "locked" I can quite easily slide the front bar all the way to the back bar. Only thing I can think of is adding a thin washer to the assembly to make a tighter fit. I just couldn't seem to find one the right size. Most washers are way to thick and I can't lock it down.

 

What year is your H3? The H3T might be a different setup then the H3. I know they made some changes in '08 for the H3. From the top of the track they look like the metal has been rolled over every 3 1/2". If you put your finger in the track, and slide it along the under side, you'll feel them.

 

i noticed if i get mine too close to the end of the track it won't hold properly.

 

It's a 2010, I guess I'll just hit up home depot and pick up a few different size plastic washers and see if I can get it to lock in tighter.

 

I have a 2010 H3 and it has the notches. I also have the roof bars and had the same issue but found if I moved them into the notches (as Broker Halo mentioned) it locks perfectly. I wonder if they did something different for the H3T.

- Jason