Limited Slip Mod

The main benefit: Increased traction at the rear tires.
Part Number For The Grease: N/A
(Normal Automotive Wheel Bearing Grease Can Be Found At Most Auto Parts Stores) 

Well, this really isn't a true limited slip mod or hop-up, but it does make
for better rear drive action. To start, you will need some automotive
grease. The thicker the better for this project. You will need to tear down
your T-Maxx all the way to the ring and pinion gear box. Take the
gear box out of the truck. If it needs to be cleaned, now is the time to do it.
Once its clean, open it up. Make sure to take notice of the ring and pinion
condition. Also make sure you know what spacers/shims (if there are any)
go so they can be placed back where they came from (very important for
ring and pinion life). If your ring and pinion are damaged, you should
probably get some new ones, but I will leave that up to you. Remove
the ring and pinion and differential assembly. Clean all of these parts
at this point. Now remove the ring gear from the differential housing.
Check your spider gears for wear. If they are damaged, you should replace
them, but again, I leave this up to you. Remove all the gears and anything else that
might be in there (you never know, Traxxas might start shimming these). Clean
off ALL the lube from the gears. Also clean ALL the lube out of the differential
case. Now get out that nice, thick, and sticky automotive grease. Reassemble the
differential assembly using the automotive grease (pack the case full of grease).
Also make sure that you replace any shims to the original positions they came
from (if there are any). If your ring and pinion show signs of damage,  you should
check out the "Pinion Saver" mod (you will find it in the mods table on the main
T-Maxx page of this site). Put the gear box back into the truck and complete
reassembly. After you have everything back together take your Maxx for a run. You should
notice the back tires turning much closer to the same speed than before. The
automotive grease acts like a glue almost and helps lock the wheels together, but
should still allow them to turn at different speeds so turning isnt messed up.
This is not a good mod for the front differential. This will cause hard
turning. If you do lots of pulling and climbing, then you might have better
luck doing this in the front, but you will see your steering go right down
the tubes. I hope you all enjoyed this cheap and easy mod.

Update: If you can get your hands on some 30,000wt silicone grease, use it.
From what I hear, it works the best. If you cant get the 30,000wt
the auto grease still works ok. I think Kyosho makes the 30,000wt.