Wow, I had no idea that people keep track of that ....but I should have, knowing how involved a restoration can get on other vehicles.

ours is a 54 model machine and has the plate steel fender rather than sheet metal. so it would be early 50s that the change happened

It appears that that change was from 1947 until sometime between 1950 and 1951 depending on the serial reference that you use, and in some cases the parts book you use:)

Lots of changes overall along the way from 4G1 and 7U42***. Some backwards compatible, others not…lots of discussion over the past two decades about these on the forum.

My own observations about heavy plate fenders; factory originals had gussets to reinforce them. It seems the add on heavy fenders did not; I have had to stiffen some up that had fender tanks bolted to them, due to the excess weight and vibration. JM

Yes Skinner is looking at what I was commenting on. Not that I see this as a major red flag. As long as finals are not leaking large amounts of oil, it would indicate bearing are Ok. Just interesting to know more of the history of these old survivors.

Before my time my father pulled a large combine with a D4 (no idea which model D4, but before 1952). The tongue weight ( the front wheel was removed) cause final drive issues. So he got a D6 for the next season.

Some how, I was thinking east coast not west. Because the shield of the fuel tank on the right fender was looking very Fleco, but not seeing the same on the left was not sure. But since Fleco was from Oregon, this is almost a sure thing.

Comments about the side mounted fuel tanks, did the stronger fenders come to D2&4 before a D6?

Ray, You mention the stories this tractor could tell from all the wear it shows. I agree there is a lot of wear. One place is with the blade cylinders. The dozer was stored with the blade down, as we jacked the blade up the shaft becomes exposed. With the blade up there is almost no chrome left on either cylinder shaft. No rust, and no pitting was noticed, but the chrome was almost all gone. I wish I had a picture of that. I don't know the age of the blade setup, but once installed it was used a lot. Possibly the cylinder shafts were thinly chromed to begin with, but to have it worn almost completely off makes me think this machine was primarily used for building skid roads/logging roads. Left cylinder has leaking on the way up too, so I'm going to have some expense fixing the cylinders. There is a plate on the back of the blade that probably tells who made it, and maybe a serial#, but it is painted over. Who knows it could have been a used blade when it was installed too.
There is a serial # showing on the winch, does anybody know what year it corresponds to? It could hint at when it was installed, but like the blade whether it was new, or used when installed is unknown. One thing I noticed when looking at pictures of older machines like this one, is they all have this style of blade with the hydraulics pushing the blade up, with the bottom of the cylinder toward the front. The newer machines have that turned around.

I saw where Fleco was mentioned as a probable make for the canopy. I didn't know that was an Oregon company. I do recall seeing other dozers with a canopy like it in the past. I live close to a place called Powerland. They have a large building dedicated to Caterpillar, and I try to go to the Steam Up every year which is their big show, over 2 weekends last of July, and 1st weekend of August. Being that Hyster, and Fleco were Oregon companies makes sense those products are on my dozer. I have for sure seen them at the Steam Up.
The Willamette Valley in Western Oregon is a very fertile valley, but I've not associated crawler tractors with farming here. Lots of hay, row crops, grass, but I've associated crawlers with construction, and most certainly logging. If I was to guess that is where this Cat has always been.

Hi, R2D2.
Before the Hyster logging winches, there was an outfit named Williamette making logging winches - no prizes for guessing where they were based or why they started making logging winches. Their winches were a bit more 'primitive-looking' with castings for the framework. I suspect that Hyster may have taken them over.

Just my 0.02.

A quick google search said Hyster was founded as Willamette Ersted Company in 1929. Making winches for the logging industry in the PNW. I'll keep my eyes out for a Willamette Winch. Maybe see one at the Steam Up next summer.