around the tail gate this is good stuff
for the bottom of the tail gate
https://www.amazon.com/BLOCK-Tailgate-Cover-4-25-width/dp/B00BPE4AP6?pd_rd_w=OzYxK&pf_rd_p=e8955138-5518-43fe-a991-57b05b120e20&pf_rd_r=REYBKDZ4P3M8HNF9DBV8&pd_rd_r=2591f5b6-792d-453b-9d0c-0c282f4d5298&pd_rd_wg=G1gB9&pd_rd_i=B00BPE4AP6&ref_=pd_bap_d_rp_1_13_dv_vtp_1_t
under bedrails - the stock 3rd gen ones are better than the stock 2nd gen - line with tape and i used a silicone too (not sure how successful the silicone was)
https://www.amazon.com/dp/B01FROBUXE?tag=amazonqueryr2-20
fill gaps in front of the bed with silicone, and then work on bed storage boxes ( i sealed mine up)
this might be useful
Highly recommend sealing your truckbed first with the advice shared above. I live in Oregon and had inches of water in my truck bed right after I got the GFC installed in January. I’ve had to take the GFC off twice for water proofing the bed since then. Don’t make my mistake.
@oddball this is what I used under the bed rail. I got it at Home Depot for like $5 for a roll. It’s super thin and very sticky it’s Also flexible. It’s pretty cold here on the East Coast so what I did was took a torch and very lightly heated the top of bed so that the adhesive would take better. Then after it was applied I took a razor knife and cut just a small enough hole so when I put the cap back on the clips would go through it. Also before I put the cap back on I ran two to three lines of Permatex On top of the rubber tape on each side. I went to advance auto and found a caulk tube size of it for $20. I went with the very flexible permatex. It’s your choice but I also removed the bulkhead rail and applied three or four lines of Permatex under there also. And for the left and right corner where the gaps are behind the cab I used some duck seal also in the gaps also Got it from Home Depot. I slid the end caps out until they touched the side. Then then jammed the duct seal up in the hole from underneath. Then I ran some Permatex over it all for extra measure. Don’t remember if I read it here or over at Tacoma World but take a flashlight and laid on your bulkhead corners if you can see light coming in that means dust and water will get in. There is also 2 1/4inch gaps at the back of your bed on the floor you may want to fill those too. In the picture with the stiffeners you can see the Permatex in the corners. And then finally you have your little box cubbies in the bed you may want to seal up too. Also invest in a set of bed stiffeners to prevent your bedside from bowing out once you get your camper on your truck. I went with the total chaos stiffeners because they come all the way up to the top rail the other ones on the market only come only halfway up the side. I also wanna give a big thanks to everybody in this thread for all the tips and advice they gave me.
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Sweet thanks, man. I also hail from the beast coast so I appreciate the advice from a fellow right coaster 
New Hampshire. Live free or die!
Yes I believe that is what I used. Here’s a picture of the inside of the role of what I have left. So far so good Ive had my GFC on my truck since November. No leaking or dust coming in from the bedrails. A few tips When applying the tape make sure you don’t stretch it to much. Just enough to keep it taught when you’re applying it. When I installed it on my truck I use a heat gun the heat the top of the bed rail so The adhesive would that better. It was pretty cold in my garage. I would also take a razor blade and cut a tiny slit in each of the holes to allow your bed rail clips to easily snap in. You don’t want to make the splits too big just enough to allow the clip to slide in it’s rubber so it’ll give a little you just want to have a little hole enough for it to start to stretch. I didn’t do it on my driver side but learn my lesson and on the passenger side I did it. If you have anymore questions feel free to reach out to me. Chuck
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What are folks doing to seal at this seam to the right of the cargo tie-down rail? I will fold the weather-seal tape down over the large hole in the sheet metal. And then below that, at the seam between metal and bed side, should I try wedging some butyl tape? Should I also remove the cargo rails and silicone along the whole length of sheet metal edge?
I used permatex under my bedside cap on the bed rail. Reason I use that was it’s a little bit more flexible than silicone. And for the 4” hole on the side all I did was use some of the rubber tape I bought to cover it.
Thanks to all who contributed to this thread- have sealed the front corners and bed rails now, will do the tailgate once I get my bed stiffeners.
One question that I had is that the front rail seems to sit about 1/8"-1/4" higher than the top of the side rail caps on my 3rd Gen (2021). I’m assuming this is the case on all 3rd Gens and that the seals GFC uses / camper design account for this?
My install is coming up (6/7) so I am trying to decide if I should do anything to seal the bed rails on my 3g Tacoma. I currently have a trifold tonneau cover on my truck and haven’t had issues with much dust or water intrusion. Actually, I had expected more dust and water given that the seals don’t lay down very good over the area where the tonneau cover folds.
Here’s what I have done or am planning to do for sealing up the bed:
I’m leaning against sealing the bed rails since I haven’t been having issues, what do you guys think?
i would seal under the bed rails. its a fairly quick and easy thing to do and not very costly. its not as easy to do once the camper is on there and to me at least - the juice is definitely worth the squeeze
100% agree with d.shaw on sealing the bed rails.
sorry, total newbie, did you have to remove the bed rails, or just left on bed rails, and sealed along edges? Appreciate your help
@bomendoza remove them. its easy. pull up from back edge - its a bunch of plastic clips. im about to get on a flight. there are decent “how too” about.
Thanks guys, I’m going to seal them.
