Your truck is a wet weather environment. Speakers use paper foam on their surround and it rots out faster than you house speakers. I learned a trick that is free to refoam my speakers without buying a foam kit that starts at $20 and you might even rip those kits up trying to install them.
I use fabric. I don't even use new fabric! Went into the closet and found a pair of slacks that I will never fit into again. They had lots of fabric cause they were from the days of lots of pleats. So I used a compass and a ruler and measured the speaker then drew out the lines of the fabric. Slippery polyester fabric works best. Then I ironed it flat and cut the donut out of the fabric. Crumpled the old rotten surround out of the speaker, it just fell out into the garbage cause it was so rotten. Speakers don't work if they don't have that surround in, or if it is leaking air that it is supposed to be pushing.
I mixed a little batch of Elmers wood glue up with some water and glued the fabric to the cone, and to the metal frame. Then I put the thick cardboard gasket over the top of where I glued the fabric to the metal, and glued the fabric with watered down Elmers to the cardboard cone. Left overnight.
Made a template and took speaker out to garage and used black Spraypaint to impregnate or dope the fabric making it air tight. Reinstalled speaker and what didn't play before sounded like it just came from the factory. And since I used fabric with spray paint instead of a cardboard replacement kit, this surround will not rot out like the old one did. I used Rustolium for 99 cents.
You can't even tell that it has been refoamed. And it looks like a much more expensive speaker. Expensive speakers use fabric instead of cardboard for the foam surround. Believe me, the fabric has way enough play in it to let that speaker travel enough to give you great highs and lows!!! I only found one guy that suggested using fabric. But I bet the guys who said fabric wouldn't work were the guys that were selling those overpriced cardboard surrounds on EBay. Once you do this, you will never even think about using cardboard surrounds again. I heard one guy repairs $5000 speakers with this method and has never had one sound bad. I haven't either. And it is FREE! Another thing about those cardboard foam replacements on EBAy. You could buy a complete brand new speaker for the price those guys want for their little kits. Now if the speaker has moved around a lot, check youtube on how to shim the cone in place. I have never had too, but there might come a day. I wouldn't buy the shims either!