The best way is to have it professionally cleaned, my sons truck had the same smell and he had it professionally cleaned and it took the smell out.
Purple Power 4319PS Industrial Strength Cleaner and Degreaser, dilute it at least 4 parts water to 1 part degeaser finish with a carpet cleaner/extractor & chemical ( P21S TOTAL AUTO WASH ) can you get the carpet and pad out of truck cab? that would be good way to clean it without messing up interior of truck much easier to clean/scrub/rinse carpet too.
then you'll have to do this while it's in the cab,rent a carpet cleaner/extractor or use a really good shop vac to pull out solution & water after scrubbing and go to Goodwill and buy a bunch of old towels so you can blot the hell out of it. better to use degreaser/chemical solution that is watered down a little more and do it multiple times than use the cleaner/degreaser stronger and you won't be able to get that out either. household DIY solutions won't do anything for gear lube ; you could always rip up the carpet and replace it
Clean with vinegar/water solution. Then let dry. Then apply baking soda and let set for awhile. Then vacuum.
I've tried this and the smell is still their