I would install a Tranny temp gauge if you don't already have one.
I would then add a tranny cooler or maybe an additional one if need be.
Find out what the tranny experts say safe tranny op. temps are.
I found interesting specs to compare 2 Honda vehicles,3500 vs 5000#'s .
Most all FWD mini vans since they first were developed have 3500 tow ratings and I wonder why ? It seems by now, the mfg.'s would increase those ratings due to horsepower/torque improvements .
Honda Odyssey
Towing Capacity - 3500
Displacement (cc) - 3471
Horsepower @ rpm - 244 @ 5750
Torque @ rpm - 240 @ 5000
Curb Weight - 4384
Wheelbase - 118.1
Length - 201.0
Gross Vehicle Weight Rating (GVWR) - 5952
Gross Combined Weight Rating (GCWR) - 8410
Honda Ridgeline
Towing Capacity - 5000
Displacement (cc) - 3471
Horsepower @ rpm - 247 @ 5750
Torque @ rpm - 245 @ 4500
Curb Weight - 4500
Wheelbase - 122.0
Length - 206.8
Gross Vehicle Weight Rating (GVWR) - 6050
Gross Combined Weight Rating (GCWR) - 10085
Honda Odyssey
Ratios:
1st gear 2.697
2nd gear 1.606
3rd gear 1.071
4th gear 0.766
5th gear 0.538
Final Drive Ratio (Front Differential) 4.312
Brake Diameter mm
Front 296
Rear 313
Honda Ridgeline
Ratios:
1st gear 2.693
2nd gear 1.566
3rd gear 1.023
4th gear 0.729
5th gear 0.531
Final Drive Ratio (Front Differential) 4.533
Transfer Case 0.537
Rear Differential Ratio 3.384
copied this from one owner who tows with a Honda O .
***
***I tow a Fleetwood Sun Valley/Allegiance with our Odyssey quite happily. But I do it well equipped with a Reese350 miniWDH, Prodigy brake controller and fairly light total load of gear. Based on estimated empty van weight of 4,500# (with options and gas) and having weighed the family, gear and options on the camper, my total weight is about 7,800#.
Haven't been to any REAL mountains yet, but I had no trouble holding speed on about a mile long 5% grade near Devil's Lake SP in Wisconsin. Of course the speed I chose to hold was about 50 mph in D3. No need to push it, we're on vacation.
Make sure to use premium when towing (read the manual). It does make a difference.
Brake Diameter mm
Front 320