Hello everyone. First timer here. I’m James from Hollister Ca. I’ve never owned or operated anything like this before, but always wanted on old dozer. I was able to get this machine for $6,000. Runs excellent, has great oil pressure and drives, hydraulics work good, has trouble steering right but with some force on the pedal after pulling the lever, it’ll turn. I’ll need to fix that. I’m sure with your help I can certainly do that. I need to have the blade tilt cylinder rebuilt, it leaks pretty good, need a couple hoses as well.
I’d like to put fresh oil/ filters and fluids in everything.  I’d like to get a service manual for maintenance/ repairs. Can you guys tell me more about the condition of the tracks? And anything I should look out for on this machine? Any special attention on some things? Thanks for all your help. I’ll have many more questions as I continue to work on this. 

More pictures 
 

Looks like a nice tractor, seems like a very good price. I have one with a bad final was going to fix it but could not find parts.

Welcome aboard fellow D6B owner! That's a good looking tractor. The most important thing I can tell you is that the hydraulic pump for the D6B is no longer available from ANY source. Please only use AW 32 hydraulic oil and change it often. Don't use cheap universal tractor fluids! 
The manual you need first is the Operation and Maintenance Instructions(OMI) I found one on eBay:
www.ebay.com/itm/234581040090
Your pictures are good, I was able to see great detail. The undercarriage looks very good, your track rails are Caterpillar 3P7153 and the sprockets are segmented. This means your tractor has been converted to later model D5 track, excellent! 
Your engine is turbocharged. The D6B was naturally asperated unless equipped with the optional "high-altitude normalization turbocharger." More good news.
Back then Caterpillar used separate manuals for the "bare" tractor, the hydraulic system, the blade and any other option etc.
The ACMOC library has copies of all the manuals for the D6B. You can access them by becoming a paying member for $44/year.
Craig
 

Your tracks are kind of cobbled up.
There are at least 2 different rails on them.
they have been run on wore out bottom rollers.
The pins and bushings are approaching 100% worn.
The rails are spalding kind of weird.
If you are actually going to use the tractor the blade needs to be reskined.
The injection lines are cobbled up bad enough they are dangerous.
Bob

I was in a hurry this morning and forgot to compliment you on the great deal you made. I also didn't mention that there are even Caterpillar D6B sales brochures in the ACMOC library.
Unfortunately you are being misled by Bluox, he is apparently trying to be known as our club's pessimist.
1. Your tracks are genuine Caterpillar D5 modern-style with alligator-bolt together master links.
2. There is NO sign on the track pin bushings that the have ever been close to being rubbed by worn-out bottom rollers. Those rollers can't be observed because your D6B is equipped with the optional full length track guides. btw -  another good plus.
3. There is NO photo that shows the amount of pin & bushing wear. Judging by the good condition of the other components of the U/C, I say they aren't worn very much.
4. Spalding? Where?
5. The blade-face shows signs of many hours of use, but there are no holes in it and will last a good many more hours until re-facing is necessary. The cutting edges & end-bits need replacing.
6. The injection lines have been bent/damaged some over the years. They don't show any sign of leaking and you say the engine sounds good. I see no reason to think they are dangerous.
Congratulations on a great buy!
Craig
 

Bluox, how can I fix these injector lines to not be dangerous? Here are some more pictures. I’ll work on the tracks as best I can. 

See how the fuel lines enter the nuts ,they have been bent way past allowable limits.
They actually may not even be the right ones.
there are no clamps on the lines and this allows them to vibrate and break.
When they break and the tractor is hot you are subject to instant bar b que, especially if you have a puller fan.
The only safe way is replace the lines and clamps.
Those are not Cat tracks'
If you look the idlers are out to the end of the wear strips, this means you are almost or out of adjusters.
It also means the internal pin and bushing wear is at or close to 100% worn.
See where the rollers have been wearing on the pin bosses =worn out rollers .
Look at the back of the track pads, see the groove =worn out rollers.
Your new pictures show wear on the inside of the links that suggest track frame misalignments maybe bad diagonal brace bushings.
Looks like the bottom rollers have been recently changed.
The spading on the rails is not normal wear.
A disclaimer I've only been at this about 55 years so I have not seen it all but my Cat experience is a little more than scanning old parts books. 
If you want to talk send me your phone number and a good time to call' in a private message.
Bob

Hi, mopardude318.
To get a better idea of just how worn your pins and bushes might be, place a piece of round bar - 1 1/2 to 2" diameter - in the highest sprocket tooth that you can get it into and reverse the tractor until the track chain is tight across the top. Do NOT go past the point where the track chain becomes straight.

Then measure the distance across 4 links/5pins, preferably all of the same part #, and post that measurement here. Somebody will have the chart to tell you how much wear there is in the pins and bushes and approximately how much life is left in them.

There does appear to be some wear on those sprockets and on the wear surfaces of the bushes. I would bow to bluox's judgement on this but how 'urgent' it is to deal with it would depend on your future intentions for the machine, whether you have HYOOOGE plans for it or if it is 'for the playpen'.

Bluox is right about those injector pipes. They have been subjected to some RUFF treatment in the past. While they may not be leaking now, there will definitely be some stresses at those sharp bends and the lack of clamps will allow them to vibrate, increasing the stress on those bends. You should be able to get new pipes and the clamps from your 'friendly local Cat dealer' by quoting the engine serial #.

If they can't find them in their computer parts lists, ask them to look under "Classic Caterpillar". Many of the older machines have been 'shuffled' into this section of their listings, I suspect to reduce the numbers of listings they have to look through for most customers.

Just my 0.02.