I am in the market for a 315, 318 or 320 Cat. Other than sheet metal what were the major changes from the “A” to the B to the C series machines?
Every successive generation has more horsepower, more speed, more computers, better smoothness, and lower emissions. The Cs being the newest are the nicest to run but perhaps they're a bit less reliable than the older ones because they have more computer controls (more computer controlled valves, computer controlled engines with emissions sensors etc.)
The non lettered, or "A", as you call them, are pre 1996, non emissions controlled. The "B" models are tier 1 and the "C" models are tier 2 I am not sure of all the changes, but the "C" machines are much faster and smoother than the older ones. I think it is mainly pump and control valve related.
Actually from my experience the C models are far more reliable than either the B or A models. The C models are load sensing and the hydraulic output of the machines are matched to the controls. The diagnostics package is easy to access and user friendly. The electronics package is well refined and these machines pretty well caught up with the Hitachi and Komatsu products. The B model Cats are the first with a real comprehensive diagnostics package. It wasn't real easy access or understand. I found the control of these machines to be somewhat jumpy and you had to throttle down the engines to do precise moves such as setting thing in place. The A models had an electronic system in them but part of the access to the monitor and diagnostics was hidden. One of the buttons is not marked on the monitor panel. I also found these machines to be a little jumpy and many owners I talked to said they liked plenty of fuel for each day of work. Now the good part of all these machines is that the hard parts are real good. Rotec bearings, car bodies and houses were all real tough. I've looked at many logging machines with more than twenty thousand hours on the clocks with just an engine, pump and a couple of undercarriages. Granted there was much left to make money with but I have yet to see any other brand of machinery in that application to have operated that long with so few of major repairs. One other thing is that the D series are now out for many of the models.
You can read my mind That's is exactly my personal experience with CAT diggers. I personally much prefer the C series over the As and Bs. They are all very reliable machines in my [limited] experience (in the 11-45 ton classes that is). I once ran a 330C with 23k hours on it with just one engine rebuild done at 21k hours and the pump replaced at 15k hours (and of course several undercarriages and probably a few little things), and it ran like new - literally. Perfectly smooth and very fast; a wonderful machine it was. The As and Bs are fine too, but not quite as fast or smooth as the Cs. I've heard some grumble about electronic gremlins in some Cs, so I mentioned that they may be a tad less reliable but I haven't experienced any such issues myself.
We have never had any electrical problems with our 2 320Cs, and the 320B is running just as strong as ever. With the exception of the 320B being a little more wore out and having just a hint of slop, I can't really tell a difference in the way the controls handle compared to our Cs. The 320Cs have a little more grunt though. Thats just my opinion though