I found books for D6C 76A on eBay:
The service manual is a Jen Sales reprint, I like the originals better.
Craig 
Operation and Maintenance Instructions:
www.ebay.com/itm/394187656384
Parts Book:
www.ebay.com/itm/394198293720
Service Manual:
www.ebay.com/itm/255162013089

I have some Jensalles manuals, they are very acceptable and reasonably priced.

Hello johnnystc, I apologize for misleading you on the serial number of your D6C. I like helping people with their questions when I can. I usually rely on the S/N of the machine, but in your case you had only the year 1968. I had a 1968 D6C 10K373 and I ASSUMED that meant that all U.S. built 1968 powershift D6Cs were 10Ks. I proved again what "assume" can be an acronym for. 
Sincerely,
Craig

Seiscat,

Thanks for taking the time to provide inputs to my dozer issues.  My next step is to get it to a shop, either Cat (probably) or others.
 

For the record....the 76A uses a D333a engine (4-1/2" bore) the early 10K's use a D333c engine (4-3/4"bore).

Old Magnet, thank you for noticing my mistake. 
johnnystc, I think you should get the manuals I listed. The shop you take it to (even Cat) might not have the information they contain.
 

yes actually that is how edb got some of the data books he has. once they were a certain age management decided we dont need these old books any more and sent them to the bin.
luckily he was able to rescue a few for posterity. so good idea to have your own copies. i have been able to help others by scanning or photographing pages from the books i have. our dear leader shared a link a while back for the cat publications site it was surprising what reprints they could provide.