Bouncing vehicle with invisible chassis

I've got two problems that I can't resolve and hope some of the artist here can shed some light. I'm developing a vehicle who's static model exported fine and had working tires in-game. As soon as I added an animated suspension my model's geometry was scaled down so small that only the weapon and one of the tires was visible and even then it was all compressed together and bounced around the terrain before disappearing into the void. Since then I've adjusted the scale so that the mounted weapon and all four tires are visible but the chassis is now transparent and it still bounces wildly around the landscape.

I'm not sure why the chassis will not render but I do think its there since all the mounted components are attached where they need to be. Its just the body of the vehicle is not being rendered as visible. And I'm concerned why the geometry got scaled down. I already had it scaled properly so why would it get shunk on export? Can anyone suggest things to check? I'm using Max 5 and the animated suspension is rigged using Look At constraints.

Thanks.