I bought this well used 1988 Astro ( V6, Vortec 4.3 liter, rear wheel) not long ago. It drove great in the test drive, and I drove about 150 miles home in it, was a dream. The old owner said it needed an oil change, so before I did very much ( hadn't done anything but get the windshield replaced and took the cat to the vet) I went to one of these quick lube places and got an oil change. Did my errands and came home, next day when I started it, there was some smoke when I started it (Not some huge sun blocking cloud or anything, just a puff, grey white.). Didn't think much of it. Drove fine, then noticed when I took a turn at a major intersection it started this little knocking as I was turning, like a fast ticka ticka ticka ticka ticka , with a little smoke, and then it 'straightened up.' (Definitely under the hood, not axles or anything like that) I got it home and told my husband; he was perplexed and checked my fluids. MY OIL WAS TWO QUARTS LOW. Needless to say, I was RED HOT. That was the LAST thing I thought could be the problem as I paid for a service ('professional' oil change, just a day before-- I can assure you, I WILL learn to do this myself...NEVER AGAIN
). Thing is, I am NOT losing oil or fluids of any kind on the driveway. So we put some more oil in it, as well as some 'no smoke' stuff in the oil tank, as well as some of that Lucas 'tune up in a bottle' stuff in the gas tank. It seemed to help, but it started running weird, like it wants to just stall in 2nd gear or something. It has his high pitched eeeeeeeeeeeee until it finally 'shifts' into gear. It seems like it wants to just kinda stall, but once it gets past this little lump, it's fine. (Sometimes, it seems like it doesn't want to get out of the little lump.) When we stop at a light, the process starts all over again. Some days it's more noticeable than others. It never dies or strands me or anything, just at times it doesn't seem to want to 'go' faster than 35 mph - it's a little un nerving because you don't know what's next! lol)The past few days I haven't noticed smoking or the ticka ticka ... My question is, is this the tranny, or just in need of a tune up, or what? Any products you can recommend? Am I damaging it by driving it like this? (I know that's a dumb question.) I don't have a lot of money to have it looked at, I was wondering if anyone has had anything similar, and if so, what was the outcome? I'm a bit sick about it as I have a feeling the twitjobs at the oil place having didn't put enough oil in it , on top of it's really old to boot, is not working in it's favor. What should I ask about when I DO have it looked at? The mechanic would do himself a favor by taking it around the block so he can hear and feel what the vehicle is doing, but I don't know if they do that. lol I just don't want it to stop abruptly on the freeway or blow up or something. I don't know that much about these things. 
It's just a great old van that I have QUICKLY become attached to. lol Any advice would be most appreciated. 
