Hey guy's, thanks again for this great thread! everything I have read everywhere on this suggests that 30k is stock in front and rear but some chose to run 50k in the front, just going over my owners manual and it states that 30k is stock in the rear but 50k is stock in the front, if I wouldn't have read the manual I would have just put 30k in both, so with that said I guess I need to order some 50k before I do the fronts, I ordered to complete diff for my sons digger front end since I trashed the first one I put in there and I assume that has 30k in it? so I'll change it to 50k before I put it in, here is what it says in the merv owners manual about 30 and 50k.

Tuning the Sealed Gear Differentials
You model is equipped with sealed, bevel gear differentials. The
differentials allow the left and right wheels to spin at different
speeds while turning. You can increase or decrease the torque
transmitted between the left and right wheels by changing the
viscosity of the silicone oil inside the differentials. The viscocity
of the oil is indicated as a weight (W). Higher weights are more
viscous, meaning the oil is “thicker.” Lower weight numbers are
less viscous, meaning the oil is “thinner.” Filling the differential
with higher viscosity (thicker) oil “tightens” the differential,
transferring more power to the wheel with the most traction.
Filling the differentials with lower viscosity (thinner) oil “loosens”
the differential, transferring less power to the wheel with the
most traction. Traxxas sells a variety of differential tuning oils
specifically designed for use in your model.
Your model’s gear differentials have been tuned specifically to
provide balanced handling and precision power slides. The front
differential has been filled from the factory with high-viscosity
50,000W silicone oil. The 50,000W oil allows the front wheels to pull
the model through the turn when counter steering through a drift.
Increasing the fluid viscosity increases the authority of the steering
while drifting, but decreases the steering when not drifting (“grip
driving”). Increasing the front differential viscosity too much will
make the model difficult to drive (“twitchy”). Decreasing the front
differential viscosity will decrease the ability of the model to drift,
but will increase steering response when grip driving.
Front Differential oil viscosity tuning suggestions
• For drift cornering with a single Series 1 battery (6-cell
NiMH), use the stock differential oil.
• For drift cornering with dual Series 1 batteries (12-cell
NiMH), use thicker/higher viscosity differential oil (higher
weight number).
• For grip driving with single or dual batteries, use thinner/
lower viscosity differential oil (lower weight number).
Tuning the rear differential fluid will allow you to fine tune the
amount of angle the model will exhibit during a drift. The rear
differential is filled with 30,000W oil to keep the rear of the
model from sliding out completely when drifting around a turn.
Increasing the viscosity of the fluid will cause the model to overrotate resulting in a spin. Decreasing the viscosity of the fluid
will reduce the model’s drift angle. For grip driving, lowering the
viscosity will allow the model to turn more easily.
Rear Differential oil viscosity tuning suggestions
• For drift cornering with a single Series 1 battery (6-cell
NiMH), use the stock differential oil.
• For drift cornering with dual Series 1 batteries (12-cell
NiMH), use thicker/higher viscosity differential oil (higher
weight number).
• For grip driving with single or dual batteries, use thinner/
lower viscosity differential oil (lower weight number).