3.8" Stock wheels?
Ah, ok. Maxx Chevron's.
Those are 5.75" tall wheels.
Trenchers are 6.89".
You'll want to gear down, if you want to keep your performance the same.
I run 19/65 on 6.5" Trencher-X's. It gives about a 1.14:1 rollout, on 5S LiPo.
Stock E-Maxx is 17/68, which could possibly give you the right gearing depending on your setup. Do you have the Brushless E-Maxx, or the Twin-Titan 16.8v E-Maxx?
TRX E-Maxx - KD 2039kv/HW 150A | TRX Summit - DeWalt 14.4v/TRX EVX2
TRX Slashapede 4x4 - Vel. 3500/HW SC-8 | TRX Stampede 4x4 - Vel. 3500/BL Hobbies 120A
Ofna Ultra LX-2E -KD 2400kv/HW SC-8 | Losi E-Muggy - Leopard 2000kv/HW 150A
KM Baja 5b - 30.5cc CY 2-Bolt