Can anyone identify this? I don't even know if it's incomplete. Scrounged from one of my son's old toy tubs - probably purchased (or received) about eight years ago.

It's solid gold, worth thousands...

 

With the exception of the nose and the orange hub caps, looks fairly generic to me. 

I'd say it's 8952.  The orange parts (60934) are Tridax Pod halves and come in a few Bionicle sets.  I'm guessing your son was a fan as I don't believe more than one of these halves came in any set.  Funny enough, if you put two of those together, you get the hologram Death Star in 7754.  So, you own a Death Star and will be rich one day!

You have to start off by identifying the most unique pieces. Loghamel is right about the orange part. It is pretty unique and rare to find. according to bricklink it only comes in 6 sets. 

http://www.bricklink.com/catalogItemIn.asp?P=60934&in=S  you can check out which sets they could be by this link.

8961 and 8952 both came with two of those orange pod halfs... Your son likely had those sets given the dark red and lime axle connectors with ball socket.

Now you have a pile of parts worth very little. Keep scrounging.