Originally Posted by Tarheel
Based on personal experience with Airstream data, do NOT trust it. Measure your ball height yourself, as Reese tells you. Airstream data was off almost 2 inches on ball height for my 2002 safari. I'm not saying that 18.750 is wrong, but the only way to know what is correct is to measure.
Based on the original post, it is probable that the only problem is that the tounge load has increased when the trailer was loaded and the spring bars need to be tightened a link or two.
Here is what Reese says about ball height in their instructions:
1. Line up tow vehicle and trailer on level pavement, in straight-ahead position, uncoupled.
2. Level the trailer and measure and record the distance from the ground to the top of the ball socket (X dimension Fig.1).
3. Select a hitch ball with a diameter that matches the trailer coupler size. The three most common sizes are 1-7/8", 2", and 2-5/16". Select ball with 1-1/4" or 1" threaded shank that is V-5 rated equal to or greater than trailer gross vehicle weight rating (GVWR). A thin jam nut (.72” thick) should be used on standard ballmount to prevent interference with spring bar trunnion.
4. Attach hitch ball to the ballmount (G). REESE standard height hitch balls with 1-1/4" shanks are supplied with lockwashers and nuts (If you must use a 1” shank ball, use bushing 58109 (B) to reduce hole size in ballmount (G) to 1”). Always use a lockwasher and place washer next to nut. Unless otherwise specified by ball manufacturer torque ball nut to 450 ft/lbs for 1-1/4" nut, 250 ft/lbs for 1" nut.
5. Some installations may require a longer hitch bar (D). Extended bumper guards, pickup truck "caps", or rear mounted spare tires can limit turn angles unless a longer bar is used. Individual hitch bars (D) are available in various sizes.
6. Insert the hitch bar (D) into the hitch box and install a pull pin. Place ballmount (G) onto hitch bar and move up or down
for proper height. Hitch bar may be used in either the up or down position (see below).
NOTE: Ball height should be greater than coupler height (measured in step 1) to compensate for vehicle "squat”(approximately 3/4” to 1”).
Hope that this helps.