D7 3t vs 17a 7s blade differences

Same blade but the 17A uses a different sheave group.

Please forgive my ignorance but would a sheave group be what I consider the mounting bracket that bolts to the tractor or the arms that go from the blade to the mounting bracket? As I am sure you can figure out I would love to take the extremely tight blade mounts and arms from a 3t and put them on the 17a. Second question is there anything particularly desirable about a 1944 wartime d7 serial no 3t297sp?

Thanks for responding and for the help.
Jason

Hi, White Halftrack.
The 'sheave group' refers to the cable sheaves on the blade lift. The 3T used a 4-part reeving - i.e., 2 sheaves each at top and bottom giving 4 falls of cable - while the 17A used a 6-part reeving - i.e., 3 sheaves each at top and bottom giving 6 falls of cable. If at all possible, i would suggest retaining the 17A sheaves if you fit the 3T blade as it will give a finer control and be easier on cables.

Just my 0.02.

That makes sense. Thank you both. Essentially I could just pull the pin and leave the sheave group in place if I switched blades. Awesome. Thanks for educating me. These old cats are pretty amazing.

It's not just the sheave arrangement that is different between early 3T's and the 17A. All the sheave part numbers are different (I suspect different diameter) and the upper sheave mounting bracket and corner sheave arrangement are different for 3T11973-up and the 17A-up. Probably due to cable alignment requirements.

Hi, Old Magnet.
The content of your reply about the sheave differences would not stop White Halftrack from doing as he said in his last, post would it? He suggested simply pulling the pin from the lower sheave group on his 3T dozer, leaving the lower sheave with the 3T and attaching the 17A lower sheave group to the 3T blade when it is fitted to the 17A. That should work just fine, shouldn't it?

A kew-ree-yuss mind would like to know. (Maybe two.)

Yes, if just swapping the blade lift attachment is all that is done that will work fine. Just never know who all is reading this stuff so I wanted to bring up the differences.