Towing in the Mountains with a 3rd gen 4Runner

I thought I would post my experience towing a travel trailer to the Rocky Mountains in CO this summer. The tow vehicle is a 1998 3.4 Limited 4runner with just a bit over 215k on the clock. We have owned the truck for about a decade and 115k miles. I replaced the radiator about 5k ago. I do not have an aftermarket transmission cooler. I did replace the rear springs with some 2906 Rear Coils and some Bilstein 5100 Rear Shocks. I have a Blue Ox weight distributing/ anti-sway hitch.

I was a bit concerned that the 4runner may not be up for a trip out west prior to this trip. We live in a fairly hilly area and the 4runner does the job but it can barely maintain 55mph on some hills. Planning ahead and getting a run at things helps a ton but it does not make for a particularly relaxing drive. So far most of our trips have been under 400 miles from home. We have taken the 4runner out to the rockies one time it was loaded the to gills with 4 people, bikes on the back and all our gear inside. It maintained the speed limit but it was using most the power the automatic would freely give. It maintained the speed limit with just a bit more spare capacity.

OK back to this trip. I did not weigh the whole setup but from my best calculation I would say that the trailer plus gear/water/fuel/ people was around 3500-4000 pounds. I will start when we got on 70 West through KS. The first day on 70 we made it about halfway across the state. I ran about 68 for most of the trip and would drop down to about 60mph on a few hills. The second day was a bit rougher. We had a pretty decent north east headwind. That combined with some of the longer climbs would cause the cruise to give up the ghost. I was trying to maintain 62mph and I could not. The wind let up about halfway to Denver and things were a bit easier. Once we got to somewhere around Morrison I never left 2nd gear and spent a fair bit of time in 1st at around 30-35mph. I really could have used an extra gear between first and second. I headed north on 40 towards Winter Park. There was no traffic and having access to 2 lanes all the way up made the drive decent. I kept it in 2nd most of the time and just took it easy. Transmission temperature sensors weren't cool in '98. I meant to throw the digital thermometer in my tool bag but I left it behind by mistake. The trailer brakes did a fine job on the way down. They did get hot a bit towards the bottom of 40 but I was trying to give the transmission a break. I never really had any noticeable fade. MPG came to about 10.18 to this point. The worst was the stretch when we were fighting the wind and that was 8.8. The fuel guage is a bit wonkey, but this is primarily in the top half of the tank and it seems pretty close for the last half. I still don't trust it though so I went by range for the most part. I Filled up every 130 miles or less and carried a 5 gallon can on the tongue just in case. The range is the worst part of using this guy as a tow vehicle in my opinion. Anyways, we made it to Grand lake and setup camp.

Running around the mountains we got nearly 20mpg on one fill up. I have never seen this truck get that high. Normal mpg is around 16. The trip back seemed a bit easier. The worst of it was the climb up 40 from winter park. It was 2 lanes for the trip down. I did pull over a few times on the decent to let people pass since I was taking it easy on the brakes.

About an hour from home I did start to have some weird electrical issues. I do have a Bluetooth OBDii gadget hooked up to the port. It was showing about 8.7-9.9 volts. My battery dummy light came on while on the interstate going 70 while passing an extra slow semi. I just started loosing power, not a lot but enough. I ended up stuck beside him for way longer than I would have liked. I did eventually get around him and I was stuck going about 60.

I pulled off and I found the vent fan on with the vent barely cracked. I wondered if that vent might have gotten pushed closed by the wind and in turn caused the fan to pull a bunch of amps. I got back on the road. My tack was flipping on and off. I was able to go about 60 on the back roads. I was still showing around 9v. We did make it home. While backing the trailer in I went to roll the window down so I could hear my spotter and that was the final straw. It died and didn't even pretend to try to start. I tried to charge the battery a bit the next day and it was having none of it. I took it in to the parts store and they got it charged up and ran some load test and said it was good. I went home with an alternator. I put the battery back in and it started right up. I then took the battery terminal off and let it run for a bit. The voltage varied between 12-15v with the battery disconnected. I also found the trailer deep cycle battery completely drained. I am not a fan of intermittent electrical issues so I would like to get this one figured out.

I am still working on diagnosing this issue. I got the trailer battery partially charged back up and it seems to be nearly drained again. I am still playing catch up at work so I have not touched anything on the trailer to see what might be draining things. Any advice on testing/troubleshooting would be greatly appreciated.

TLDR;

I towed a trailer weighing about 3800 pounds from about 900ft to 11,300 and and back, for for a total of about 1900 miles. Mileage was about 10mpg and the fuel stops were frequent. Control was excellent and I never felt out of control even when being passed by semis. 

Overall I am pretty happy with how things went minus the electrical issue at the end. I will probably do it again next year but I am not totally sure.

https://imgur.com/gallery/E10oCFX