I was wondering what the differences were between the two helicopters?

They appear quite similar to an inexperienced helicopter viewer.

Also while asking what changes were made from the A version to the D?

Thanks for your answers and patience in advance!

The differences are many, but to a dude on the ground deciding which is which, it's relatively easy-
The CH-46 is distinguished by the three landing gear and wide sponsons at the rear of the fuselage. The CH-47 has four landing gear, and narrower sponsons running the length of the fuselage. As for the differences in A and D models, no clue. I know it has to be more than avionics if Trumpeter is releasing a different rear fuselage for the D. I"ll be jumping a Chinook this weekend again and plan to get some good shots of it time permitting.
My A model should arrive tomorrow, bought for $95, but I'm already thinking I should've waited. I want to do mine like the ones we use, with the static line anchor cable installed. I'm fairly certain we're using the C model. Last briefing we got the crew chief said that the old A model leaked hydraulic fluid like crazy, and if the leaking stopped, you were in trouble, but that the C was different-if you see a leak, or anything you're not sure of, you might want to say something and hook up.

CH-46 is smaller than the CH-47. It is shorter and narrower, also has a smaller payload. SeaKnight has small sponson, as opposed to ones that run the length of the fusalage on the Chinook. SeaKnight also has a tricycle landing gear (3 points) and Chinook has a quad (4 point) landing gear set-up. CH-47 also has two, large external engines, CH-46's engines are contained within the fuselage. There are lots of others, but those are the basic Helo ID ones.

Here are a couple size comparisons:


More here.

Internal differances.
CH-46

CH-47

(Not me in the pics, just gives you a guage for scale.)

The Chinook:

The CH-47A was the original version. The B,C, And D had various upgrades. The most obvious external differances are in the rear sail area. On the D model, there is a large vent for air flow and transmission cooling. It required a new shape and squared off front to the sail. The blades are also shaped differently, with the D having a wider and more rounded profile. Late A's forward also had a single rear wheel as opposed to a dual set-up. D also has two cargo hooks, as opposed to one.

CH-47A


CH-47D


Trumpeter looks to have the A and D parts down pretty well on their new 1/35 models. The D is due out later this summer.

Sail:
A

D


Rotor Blades:
A

D

Two cargo hooks on the sprue too.

Hope that clears it up.