Need a new driveshaft

Are you sure?  Perhaps you should reread (and then rewrite as a full sentence) your first two words!  "Sorry, Gramps" is not a complete sentence.  It is obviously a diminution of "I am sorry, Gramps."

I urge you to GET up to date on what the kids are saying, because very soon "the kids" will be in charge and WE will either speak their language or become increasingly insular.  Change and grow and evolve or become irrelevant. 

When you see something that you dont understand, take the time to look it up.  Wikipedia (created by a guy from Huntsville, Al) and dictionary.com are both very reliable places to start.  When someone makes a claim that you find hard to believe, research it, and determine its veracity for yourself!  Duckduckgo (the search engine I use) has almost the sum of all human knowledge right at your fingertips.....why not use it?

AFAIK is commonly, frequently used in terse writing these days.  The earliest usage of it on this forum was in 2005 (by Al Dolney), and that's over 14 years ago.

Thus endeth the sermon.  Can I have an amen from the choir?

That's where Im going for my next one.

Incorrect.  On several counts.

You said "I still write in complete sentence" which is wrong on several counts.  First, the sentence immediately prior to the statement was NOT complete (on this point, I dont give a fart in a hurricane what Google says, I will stick with Harbrace), so its factually inaccurate given your intent (more on that in a second).  Second, it has a mismatched object.  It would have correct grammar to state (but still inaccurate) "I write in complete sentences,..." otherwise you have had to never written another sentence, which on second thought might be a good thing, or else you could have written "I wrote in a complete sentence, ..." 

No matter how you twist it, "sorry gramps" is not a complete sentence.  Its *meaning* might be well understood since its common slang and is a vernacular diminution, where the subject "I" and the verb "am" are understood or inferred.  I can also be pretty certain that you are NOT, in fact, sorry, so its inaccurate there as well.  Sorry means either despicable, which I know you arent, or apologetic, which I suspect you also aren't. 

I will stick with my Harbrace College Handbook for grammar. 

BTW, you actually argued my point for me.  You wrote "I write in complete sentence" which when spoken could be taken as "I write incomplete sentence" which I would argue is actually more accurate.  Your intent of course, was not "incomplete" but "in complete".  

Isn't English a stupid language?  This is more fun than I have had in weeks.