Are the stock diffs that weak? Even on 4s if they are not shimmed correctly, they will not last long. I blew 2 diffs on my mbx-5T due to my own stupidity of improper shimming
check to see if these might fit...
http://www3.towerhobbies.com/cgi-bin...?&I=LXLGV5&P=Z They may be stronger than the stock ones
1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S