That is called a recirculating ball nut, and they are widely used in CNC machine tools. Usually the balls get beat up first, then the nut, and finally the shaft. They also get noisy well before they die. Re-balling them is a common thing to do on the commercial units. Some are designed not to be re-balled. However at this point taking it apart isn't going to make it any worse. It is very easy to get new balls. On some designs they actually adjust the clearance by loading larger balls. If it were mine I'd certainly take a whack at it.
Gary H. Lucas
08-17-2011 07:26 PM
I've had terrible luck dealing with Raymarine on Autopilots. As a result I updated to a Simrad system. I have a working drive for an Autohelm 5000 for a lot less than the $575 repair cost. Sent me a private message if you are interested.
08-17-2011 06:52 PM
Raymarine offer a fixed cost repair on out of warranty repairs. For part number M81130 linear drive type 1 short stroke 12v drives the cost is $575 in the USA.
08-17-2011 07:14 AM
Repairing an Autohelm Drive Unit
Wondering if anyone has had experience in repairing an Autohelm linear drive unit. This is part of a Autohelm 5000 sail mounted below deck and it is the electrical "type 1" push / pull unit. Picture is below.
When you pull and push the ram unit you hear a rumbling noise. The local Raymarine dealer is saying it's a writeoff; apparently the ram is a worm type full of ball bearings and once you put it apart all the ball bearings fall out and you can never get it back in.