The "D" stands for "
Deluxe," and the "DA" stands for "
Darn
Awful" lights.:laughing::laughing::laughing:
Actually, the "DA" stands for "Deluxe" with "Advanced" features, I believe. The DA model tractors were a major styling change that included the new lights and changed hood. It also had some changes to the electrical circuits with a new controller/timer for the glow plugs and a change to some relays. The rear lights were moved from on top of the fenders to mounted on the ROPS. Also, the handrails were redesigned and moved to the tops of the fenders, and the operator seat was changed slightly in color and style. The battery was changed so it didn't outgas into the radiator like the old one. The HST models have a bigger return spring to help prevent the sticking pedal problem. There are also some changes to the instrument panel and some of the switches for turn signals were changed.
There might be some more minor changes I've missed, but I don't think there are any major changes to the internal powertrain or any of the hydraulics. The rabbit/turtle function on the joystick has been around since the "D" models were introduced. My "D" model tractor has that and I love it.

Oh yes, speaking of joysticks. I have a very long thread called "No Joy Joystick" that chronicles the sorry design of the early joysticks. With the DA models, New Holland improved on the joystick mounting design and eliminated the problem. I've retrofitted my tractor with the new part and it works great.:thumbsup:
EDIT: Reading MikePA's post made me realize my comments were slanted toward the Class III tractors. The Class II tractors don't have the rabbit/turtle function.
Also, the gear model tractors just used to be "TC" and a number. After the styling changes, they changed to add the "A" on the end. For example, the TC40 became the TC40A. Like the deluxe models, I think this change came about with the 2004 year model tractors.