When switching over from TRX carriers to RPM carriers there is a metal ring on the back of the TRX ones that gets often over looked. It must be removed and installed on the RPM carriers or the balls will pop out constantly (sounds bad?)
You still should check to see if your stockers have that ring, the balls do not pop out and back in again with the ring. If they pop out once they'll surely do it again because the plastic has ben stretched now.

Ring, can u post a pic of the ring?

Here

What, the black rings?

Yes the Rings ?

They are steel and slip over the backside where the threaded part of the pillow balls comes through the carrier. They keep the integrety of the plastic to prevent the balls from slipping through.

Little update put on Silver Springs up front, Blue in Rear and it is much better.

By the way, for anyone interested, I am selling or trading my truck. Here's the thread:
http://www.rctech.net/forum/r-c-item...ml#post7732776

If anyone is interested in a problem that was mentioned in this old thread, I have an easy fix for you...

PROBLEM: MuggyDude said his slipper was getting chewed up and he didn't know why...well, I do, because it happened to me!

Due the the "drift" that the motor-shaft has going in & out of the motor, even though it's only about 1mm or so, it's enough to cause the pinion to drift/walk forward and come in contact with the slipper...it can end badly, as mine did, but you got lucky!

FIX: All you have to do to fix this problem is to slide your pinion back on the motor-shaft about 1mm to 1.5mm, and this will completely eliminate the problem!

I also fixed the flex problem with my Vantage Carbon-Fiber Chassis completely by simply making a 2mm Carbon-Fiber brace just like the Aluminum brace that comes with the Aluminum Chassis and mounts under the chassis/engine/motor-mount...no more flex at all!