Hey when i start my truck the undercarriage shakes and knocks. I thought maybe transmission mounts but they are tight and look fine. Any advice? Also my bright light switch is not working how do i fix this?

 

Does it knock just once? A second or two?

How much does your engine move on startup? You may need new engine mounts.

What style of hi-beam switch is it? If it's the floor mounted style, they can succumb to corrosion and fail. If it's on the columb, I would start by checking relays and fuses.

 

Could be your exhaust hitting on something (heat shield or x-member)...

 

while the engine is starting up is the only time it knocks. I dont think that the engine is moving too terribly much.

It could be the exhaust ill check that.

 

Also check the bolts to the starter...the PO of mine didn't tighten them, and it nearly fell out.