Okay went to the dealer hitched up to a 2013 lr4. Still a 6 speed transmission. Difference is night and day. 75 mph flat ground she rides along in 5th gear. And will tolerate 6th as well but will down shift at times. Never dropped to 4th at all. Actually towed nicer than my 08 sequioa So now do I sell the lr3 or keep it. Lots to ponder now.
Maybe you just enjoyed the LR4 more than your Sequoia because the longer wheelbase (122" vs 112") and solid rear axle (with WD hitch) ought to do a better job or at least be more stable.
However, for what it is as an overall vehicle, I'm still basically impressed with the LR3. Last summer I towed a Haulmark lowrider 7x12 almost 4000 miles fully loaded to the maximums on the trailer and certainly over the rated limits on the vehicle when you take into account the hitch weight is a factor in payload on the vehicle.
While my loaded trailer weight was likely more or similar to what you were towing, it's a compact shape by design of the trailer which results in less frontal area to bring through the air. It is barely taller than the roofline of the LR3 but it is of course wider at 7 feet, though not as bad as 8.5 ft like a standard travel trailer. It's floor is maybe 12" off the ground so the weight is low. Also, being compact lengthwise it's 2 axles are closer to the ball mount so the whole package is probably about as manageable as 7500 lbs could be.
I'll post my CAT Scales numbers later for reference but I found that over 60-70 the mpg became really bad while staying below 70 and using downhills to roll into the upgrades helped. Overall it just took a reset of the mind than of the transmission
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I had a gross combined weight of just under 14000 with about 6500 being the trailer apparently based on the CAT scale.