Originally Posted by sohlman

See post #963 on the MRX4R thread for pics. Link below.

http://www.rctech.net/forum/3146006-post963.html

Here's the mod again.
1. Remove 3mm of material from the front of rear upper & lower arms.
2. Remove a little material from the lower rear arms by the "up screw" holes to preventing binding against bulkhead
3. Remove a little material from the right arm so the spur gear does not rub.
4. Install 3mm spacers behind (to the rear) all four arms (upper & lower). Check for binding issues (possibly not enough material was removed, or they were cut uneven, etc.)
5. Install 3mm spacers on upper body mount as pictured. Again, check for binding.

This mod works best with the 4.5 blocks & 5.0 (5.5 needs too much material removed, weakens arm)