97 w/ a loud tailgate

I have a 97 rodeo with one of thoes 3-way tailgates (the tailgate, the glass, and the tire).
Anyway, it has slowly gotten to be very noisy, The entire assmbly will vibrate in and out as I ride down the freeway. This sound quickly is driving me nuts! I anyone knows a seal or latch that may be causing this let me know. Also is this a common problem or an I just lucky?

You can adjust the latching mechanism of the spare tire carrier. You just have to play with it a bit to get it just right. Theres a little triangular nylon block that is adjustable. Yours may be worn out. Take a good look and play around with it, you'll figure it out.

You can also adjust the tailgate latches themselves. I haven't done it, but am planning on trying to get it done. It looks like you have to remove the big trim panels in the cargo area to get to the adjustment bolts for the latches of the door. The glass latch is very easy to adjust, the screws are right on the glass. If you get them all just right, it should be tight like new.

I was out their this morning working on it, and I got the tailgate and glass to shut tight, but the weight of the spare tire is causing it to keep vibrating. ISUZU only put two bolts on the spare, but I was thinking of drilling and threading a spot for a third to keep it tight.
Also, I think I need to look for a replacement one of thore nylon blocks mentioned earlier, mine is badly warped.