Been having trouble with the Integy 55t Lathe Motor, Novak XRS ESC, and 12/96 gearing in my Wheely King. I'll be driving it and all of a sudden I loose power to the motor and sometimes also loose steering. I replaced the poorly installed Traxxas VXL plugs (I tried to install them while the ESC was still on the truck.....baaaaaaad idea) with Deans plugs and I still am having the problem, just not to the extent I was before. I was using 6-cell sub C cell packs ranging from 3300-5000mAh and have switched to recently to Great Planes 1100mAh 9.6 ni-cd pack with a GP 1800mAh 9.6v Ni-MH pack due to arrive at the store probably tomorrow and I've had problems with both styles of pack. Even though the XRS is rated for 6 cells and 15t, the ESC doesn't seem to get hot or have a problem with the 9.6v pack. I was having this problem with the factory brushes and endbell so I swapped a P-94 style endbell from the 13t Kobal I had in the Pede with out putting new springs and brushes (brushes were installed last spring and barely used, springs were factory to that SGP motor.) I did swap to a heavy spring for the lower brush but have yet to swap brushes as of yet.

check soldering where wires connect to esc?

Hrm... Could be a number of things. First check the pack, all the battery bars on it should be secure and undamaged. You said you checked the battery plug so that's all good. Do like travis said and go to the esc now, check where all the wires come out of the circuit board.. After that, go to the motor, check the connections there. If at all possible, try a different motor.
Oh and do you have a diode attached to the motor or no?

Ah just go brushless, ya should get one cheap ehough working at the source! j/k Have ya tried a better esc like a Rooster or Super Rooster?

Actually, I've been thinking about going BL Bubba, been contemplating the Traxxas VXL so I could run both types of motors. I think the problems were with the ESC so I swapped in the SR I had in the Pede for the past several years and that seems to have fixed that issue for now.

I have been having the same problem with a duracrap esc thats in the bronco. Just pick up a Holmes budget setup, thats what I have in my WK, works great. If your thinking of using the vxl esc just save your money and get the Mamba Maxx, I love mine, you just cant beat programming with a pc.

Traxxas is suposed to be releasing a programer for the VXL that doesn't require a computer. I can't wait for that to drop so I can stick full VXL systems in my 4-Tec and Mini-Cooper! The Super Rooster does work great in the truck for now, but I had to put the Rx back on the servo. The SR looks HUGE on the front of the WK!