The TRX-4 is a great platform for both crawling and trailing. The stock servo horn is plastic and strips easily, so the steel one is a great upgrade (around $7 for one from Traxxas). The stock servo isn't great either, as it is underpowered if you are planning on rock crawling (would do okay if you only trail). Another thing I would upgrade is the
BEC because the internal
BEC built in the stock ESC only puts out 1 amp, which is not enough for even the stock servo under high load. If the servo pulls more current than the
BEC can provide, there is a risk of damaging the ESC. Traxxas makes an external BEC that is plug and play, but it isn't exceptionally strong and is $40 (not great value). Castle also makes one that has good specifications but with that, soldering is required in order for it to work ($27).
If you don't really want to go through the troubles of installing an external BEC, you can simply just upgrade the ESC to the Hobbywing 1080 ($45). It also might be worth it to jump to the HW 1080 if you are planning on getting the Traxxas BEC since it is within $5.
Other popular options include brass portal weights, and beadlock wheels to add more weight on the bottom (flips over less often).
Hope this helps!
