2006 Tundra TRD a slow - tow

My truck would be a turd if I was not downshifting on the inclines and declines. You should definitely do that. It would be a good idea to find a way to monitor your transmission temperatures. Things heat up quick when you are burning that amount of gasoline. Until you can monitor temps you should never tow with OD on. It says so in the manual.

 

The tow rating is usually the last number to max out. You will run out of payload long before you hit that tow rating. 15% tongue weight is pretty normal when a camper is loaded. A 7k camper could easily have a 1000 pound tongue weight. That does not leave much room for payload.

 

the exhaust and intake are tied by scissor gears so the VVTI on the 05-06 technically advance or retard timing for both intake and exhaust. its just not as advanced as the modern dual VVTI that can adjust intake and exhaust separately

the ACIS in the plenum also plays a big part with long and short runners. it switches to short at a set RPM for more power up high. long for power down low

 

The reason I asked earlier about the RPMs when you were experiencing the sluggish behavior is to see if the transmission is shifting properly.
If it isn't, it's not necessarily even a transmission problem. Here's what I'm getting at. My previous vehicle was a '02 4Runner with the 3.4 V6 (same engine as lower spec Tundras) with a similar transmission as V6 & V8 Tundras '00 - 04. I know yours is an '06, but bear with me.

When I first got the 4Runner, I was pulling my 3500 lb camper through the White Mtns and couldn't believe what a turd it was. The description you gave was very similar to what I was experiencing: I would be flooring it up a hill and it still wouldn't downshift to the proper gear. Eventually I'd be doing 20 mph in the breakdown lane. Interestingly, it ran fine in day to day driving, but put a load on it and it was total turd. I couldn't figure out what was wrong. After much research and troubleshooting I traced it to a dirty MAF sensor. Once I cleaned the MAF sensor, the truck was transformed and was a great tow vehicle.

I'm not saying this is definately your problem, but cleaning the MAF sensor is inexpensive and easy to do. It should be done as preventive maintenance anyway.

 

This sounds reasonable but wouldn’t you both throw a CEL and code for a dirty MAF?

 

VVti (Variable Valve Timing with intelligence) alters the cam profile at higher RPM's for a more "wide open" intake action. Longer duration and higher lift, like when you used to "cam" an old muscle car. Those cars run like crap at idle though since your sucking so much air. Gives it that "lumpy" idle everyone likes, but is a little stuttery off the line. VVti gives you the best of both worlds. It's the same idea as VANOS in the BMW's, VTEC in the Honda's and others. The 4.7L V8 is the same in all the 2000-2006, but the 2005 and 2006 models added VVti (and that crappy secondary air pump system). The engine has more power at the higher end when the VVti kicks in. You want the engine at high revs when pulling up that grade to use the most available engine power. Stay out of overdrive when towing. Less stress on the engine and transmission, and keeps you at a higher RPM to have MORE POWAH. You are towing near the limits of the truck, so expect it to struggle a bit at the extreme end of things (ie grades). I never towed more than 55-60mph and planned my driving for the terrain. I wouldn't have towed my rig to Yosemite either. Need a bigger truck for that. It's not all about horsepower either. Frames, brakes, transmissions, everything is upgraded on the newer higher rated trucks.

 

My 4Runner did not.

 

So just to clarify, the lift does not change, VVTL-I was lift also. But limited to the 2zz-ge that was in the XRS corolla and matrix.
All Toyota’s VVTI does is change opening and closing of the valve, aka more or less overlap, the 4.7s setup is WAY more limited than the modern engines, but it does an damn good job at providing a much larger “peak” powerband vs an older 4.7

 

The trans needs to be taken out of overdrive manually by pushing the button. It will downshift in OD but then it will upshift as soon as it gets a chance so it will shift up and down. Push the button and it won't go into OD. Yes, downshift manually to increase rpms both climbing and when descending to use engine braking.

As mentioned, reading the manual is helpful. If you don't have a hardcopy register your truck with the Toyota driver app and it will show your manual.

From the '03 owners manual:

 

I would say that it is possible this is all your truck can do.
The largest pass I’ve done so far is near the Tennessee border known as Jellico. It’s a 4-5% grade for a few miles. I believe the highest elevation is less than 3000 feet above sea level.
With my 04 downshifted to second gear I was running around 50 mph. I could have gone faster, maybe 60 or so, but if it had shifted to 3rd I would have been back to losing speed. I have a 23ft KZ that weighs ~5k loaded. It also is only 7.5 ft wide where I’m sure yours is 8, and the top of mine sits 4-6 inches lower than most “full size” campers.
That lesser frontal area helps quite a lot with wind resistance.

I would definitely check that the maf sensor is clean, and the air filter is clean, but the fact of the matter is the 4.7 is not a 400 lb-ft engine.

 

Id be willing to bring my truck to colorado for an ike gauntlet run. Need to find someone up there that’ll let me borrow a trailer. And someone else would have to video and host.