red92lx wrote:
I figured add 1000 lbs to the trailers dry weight and we got 7600 lbs. I should be able to have another 1000 in the truck and still be under, albeit not by much.
That's not how this works, you have an apple in your orange basket here....vehicles have separate ratings for how much they can carry and how much they can tow. If your tow rating is 8600 lbs and you are towing a 7600 lb trailer, that doesn't mean you have room to add another 1000 lbs in the truck.
How much you can carry is the GVWR. The weight of all occupants and cargo counts to this number. When you connect a trailer, the vehicle must carry the tongue weight, so in your case the trailer adds another 920 lbs to the truck in addition to occupants and cargo.
The fine print in most mfr tow ratings is that they are figured with only one (1) 150-lb driver in the truck and no other passengers or cargo. Every pound of passenger and/or cargo weight subtracts directly from the tow rating.
The Combined rating (GCWR) is how much the truck and trailer should weigh together.
Having owned a 2000 Expy, my guess is that with the family aboard, 3rd row folded down and stuffed with cargo, and 920 lbs of trailer tongue weight, the Expy is severely overloaded. The coil springs in the rear give you a great ride but don't have much load capacity. The last thing I did to mine was add airbags before I traded it for the burb.
If you want to confirm this for yourself, stop at a scale on your next camping trip. Friends of ours went through 3 transmissions on their Expy before they finally sold the trailer.
Regarding your sudden shifting in the rear, it was probably irregularities in the pavement. If one rear wheel drops down in a low spot or dip on the road, the soft coil springs will allow the weight to shift to that side, and then shift back as the wheel comes back up. Lateral motion in addition to vertical motion on a pothole is a pretty good indicator of being overloaded.
