RE: upgrading servo's
Traxxas 2018
SPECS: Length: 1.59"
Width: 0.77"
Height: 1.58"
Torque: 42.0 oz-in
Transit Time: 0.22 seconds/60 degrees
Weight: 1.5 oz
Hitech 645
SPECS: Speed: 0.24 sec/60° at 4.8V
0.20 sec/60° at 6.0V
Torque: 106.93 oz-in at 4.8V (7.7 kg-cm)
133.31 oz-in at 6.0V (9.6 kg-cm)
Length: 1.59" (40.6mm)
Width: 0.77" (19.8mm)
Height: 1.48" (37.8mm)
Weight: 2.11oz (60g)
I am assuming that the Traxxas servo that is listed here is for a 1/10 or smaller type RC. The torque would not be enough to drive the 1/8 scale steering properly!
The Hitech is allittle more money but it has more than double the torque! As for throttle/brake servo I am not sure, I think you may want something similar to the steering but again I am unsure!