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Note: This build log is excerpted from my web site . You can check there for larger versions of every photo or further reading.

In the beginning (1987), there was the 58065 Clod Buster. It was the first scale solid axle RC monster truck. It had a motor on each axle and four wheel steering using a single, chassis mounted servo. The suspension and steering were not too good. In 2001 we got the first Tamiya Extreme Truck (TXT-1) 58280. It used the same massive tires and wheels but moved the steering servos to the axles and the motors up into the frame. The shocks were mounted inboard and used a rocker and pushrod system. The massive aluminum vertical side frames made it bulletproof. The TXT-2 was released in 2013 and is a moderated version of the original. The side frames have been changed to a combination of aluminum and plastic, and the tires have been replaced with smaller, though still massive, versions. The shocks have been moved back out to the axles. This results in a lighter, better performing truck though with somewhat less curb appeal.

This is a four wheel drive, four wheel steering, solid axle monster truck. It uses 8 shocks, 2 steering servos, and 2 motors. It is completely unlike "monster trucks" from other RC manufacturers because it actually works like a real monster truck and therefore does not have independent suspension or insane speed. You can be the judge if this is an advantage or a disadvantage. Because the front and rear axles use different steering servos, you can use regular steering, 4 wheel steering, and crab steering if you have the right capabilities in your radio. My truck is mostly stock except for the body and the motors. I found the use of a short course truck body on a monster truck to be odd, so I replace it with an F-150 body. (I later discovered that this is a near scale model of Bigfoot 18 which also uses a short course body.) I also put in a pair of crazy brushless motors just for the badword of it. It still doesn't perform like an X-Maxx, but it is super fun to drive. This model does not have lockable differentials, but for the four wheel steering I used a pair of 15Kg Arrma waterproof servos. Thankfully there is plenty of battery space which allows me to use two Li-Po batteries for my twin brushless setup.

So what's with the name "Agrios"? According to Tamiya "Agrios, a mythical Greek giant, gives his name to this tough monster truck". That's an interesting way to put it. Agrios wasn't exactly a giant but was one of the Gigantes, offspring of Gaia who were normal size but great in strength. There were many Gigantes, and there is nothing notable about Agrios except that he was clubbed to death by the Fates. A strange choice for a mascot. He does appear first in an alphabetical list, so maybe they just wanted to pick a big monster and didn't look too closely. The graphic on the side of the truck showing a brute breaking some chains doesn't fit with any description of Agrios that I could find. On the other hand, the word "agrios" in Greek just refers to a feral or violent man. Maybe it's on a comment on the people who buy it.

The TXT-2 comes in a nice big box stuffed with goodies. The blurry and horrible picture on the right shows the plastic parts trees and the side frames.
The transmission and transfer case are built first. A set of three massive nylon gears are installed on included ball bearings. The two silver can motors share a common spur gear and use 19 tooth pinions. The motor mount is an aluminum plate.
The side frames might look like plastic, but they are actually a fascinating hybrid. The frame is black aluminum bar with plastic apparently molded around it. A flat aluminum plate is then screwed to the side. The bending stiffness of these huge plates is tremendous, meaning that this chassis is never going to flex. The cross members are mostly round metal bars. The main structural cross member is the gearbox itself which attaches at multiple points.
The axles are an interesting design with additional gear reduction inside. The initial 90 degree turn from the drive shaft is done with a pair of bevel gears performing a reduction, but this is not the differential. The differential is one stage further down and uses a spur type ring gear. The differential is an unsealed bevel gear type. This model does not include any means to lock the differentials.

The completed axles are massive. Front and rear are identical if you build with the four wheel steering option, otherwise the rear axle knuckles can be locked out. The axles are attached to the frame with long metal 4-link rods. There is a LOT more articulation here than the Clod Buster. The drive shafts are nice steel telescoping units. You'll notice that the pumpkins actually face down which looks odd but that's really how they go!
The model uses 8 long plastic oil filled shocks. Building them is obviously quite repetitive, but they seem pretty good quality typical of CVA shocks. Installing them completes the chassis.
For the stock build I used the TEU-106BK dual brushed motor ESC. I mixed the front and rear steering servos on my radio so I can turn the four wheel steering on and off. The tires were very easy to put on the plastic wheels and I did not glue them.

The performance of the TXT-2 is pretty good out of box. I added these upgrades mostly because I felt like it rather than to address any actual problem.

The TXT-2 uses eight fluid filled plastic shocks. There is nothing at all wrong with them, but when I discovered the existence of these real aluminum reservoir shocks I had to have them. As far as I can tell, these are the most expensive shocks that Tamiya offers. Not too surprising given that they are very long and include functional reservoirs. You need 8 of them for this model, and the building process takes quite a long time. The filling process is also different than other shocks because the reservoir needs to be filled and the air bled.
Here is a comparison of a new and old shock. Overall length is the same but the new versions occupy a lot more space and need to be installed so that they face away from each other.
I never would have thought of this next upgrade, but Matteo's YouTube channel inspired me. He installed a pair of brushless motors with a pair of ESCs and batteries and made the truck insane. I used the newer TBLE-03s controllers. You need to disconnect the positive wire from one of the receiver connections so you don't get double BEC power to the receiver. The picture on the right shows everything connected for a test.
Here's the completed install. Power was insane! Fair warning though: I burned up one of the ESCs within about 2 minutes. I can't be sure why this happened because I never got an over temp shutdown and it worked fine for Matteo, albeit with TBLE-01 controllers. I found that removing one motor actually didn't make much difference in top speed because the truck is rev limited, not torque limited. However, the acceleration is better with two. Play at your own risk. I burned out yet another ESC a few months later so I switched to Hobbywing ESCs and have had no trouble since.

I first built the model using the stock short course body painted in metallic black and red. It is a nice body, but doesn't look right on a monster truck. It is a bit smaller than a standard short course body from a Slash or equivalent.
To replace the stock body I chose a Ford body from RC4WD that comes pre-painted. I think it looks really nice on this truck and fits perfectly. It totally changes the overall character.

Very nice choice of hop-ups!
I get excited just by the looks of those parts-boxes, and the contents are even better!
You're spending quite a lot on this, but the result is also very nice!