track pin D7 3T and manual

You really need 4 books.
Operator's instructions which covers lubrication and maintenance procedures...The owners manual.
Parts book which covers all the parts of tractor, diesel engine and starting engine as well as attachments like electric start, lights, PTO's etc
Serviceman's reference book for tractor......only covers the tractor chasis
Serviceman's reference book for the engine. Covers both main and starting engines

Books for any Cable controls, or hydraulic controls, bulldozer etc which are not covered as "attachments" in the parts book and other manuals.

You probably need a new master pin. The master lnks you're driving it through may be stretched a little, so even a new one may not stay put. If a new pin doesn't stay put, you may have to weld it into the links on at least one side. The master pin does not extend any farther outside of the rails than any other pin, but it is slightly smaller so it should go in and come back out a lot easier than a regular pin. If the master link is stretched, maybe a regular pin would fit tight enough to work for you.

One thing you may want to check is how far the track tension adjustment is extended. If it's at its limit, you may want to consider having the pins and bushings turned or maybe cutting a link out if the tracks are not worth the cost of the turn.

ccjersey Thx I have copied info and ready to begin accumulating these manuals. The track extender I am unsure of without those books.. Seems like the front track rollers that are tensioned from hydraulics and large coil springs lying horizontally on frame between upper and lower track could be called extenders. Starter side track had quite a lot of sag when this dozer arrived. I couldn't get to the zerk good with protective shield in place but after removing I was able to get it to take a good amount of grease. The track tightened and has been ok since. Thank U all again.