hi
there are different stages of upgrading savage diffs. practically most the savage diff problems were solved years ago.
one thing is to insert those little sliding blocks in the normal housings. by now some years later that hpi has done that on their own with the x ss you may just use their cups. however imo the old mod with the sliding blocks in high quality cups like maximizer is still tougher.
next step is the bigger bearings serum already mentioned. 8*16mm on the cup and on the 43t. if you stay with plastic cups you can use the kyosho IF103 that already has a steel output that uses a 8*16mm bearing. by now one can use the new hardened ringgear and pinion.
next step is adding two more bearings into the bulks that will take part of the load.
this all works well with plastic bulks etc. of course it can all be done with aluminum parts too.
i could show you pics of all those mods but sadly our private server is down since a few days. i guess i have linked those pics before in this forum.
but here is a old link that shows most of what i mentioned. its german but you may see some things in the pics.
http://www.nitro-mods-shop.com/SB/index2.htm
the problem with the gpm housings is that they are cut the wrong way. so you have to assemble the diff inside the housings if you are using the mod wiht the two additional bearings in the bulks. so using the normal plastic housings is easier with this mod.
regardless of what mods you do on the diffs the most important thing probably is a correct shimming. not to hard and not to loose.
and yeah of course the nightmare heavy tires you use do not help preventing diff damages.
bye
rhylsadar