Internal Keyword Competition within site, HELP

Hi

On my site I had been using the same keywords on the pages, despite that some keywords fits better for some specific pages...

Here is an example:
Lets say I have a site about vehicles, a vehicle can be car, tractor, motorbike, truck etc...

Then I give the main page (Default.aspx) these keywords:
"vehicles, cars, tractors, motorbikes, trucks"

Then the page about trucks (Truck.aspx) gets keywords = "trucks"

Now I have 2 pages within the same site, competing for the same keyword.
(or so I understand it, but I can be wrong). Will this do bad for my Google ranking? Is this someting to worry about?

When I search for "trucks", I get my Default.aspx page on SERP > #300 .
Google didn't display the Truck.aspx page which is optimizied for the truck keyword.
From Default.aspx there is a link to Truck.aspx, with anchor text "trucks"....

any suggestions? is it correct of me using "truck" as keyword in the Default.aspx when a subpage is optimizied to that keyword?

I assume you want to get both of your pages ranked in google? After optimizing the pages, you can try to put more quality backlinks targeting the truck.aspx page if you want to rank it higher than the default.aspx. This can be done via bookmarking, profile backlinks, blog commenting, etc.