Hit a dear with my 08 scion tc last tuesday. Had to buy a car fast found a 08 Sentra with 143k miles so bought that within 2 day. Car ran fine, but now I heard the CVT whine when driving home from work friday.

The car said the outside temp was 100 degrees. I did stop and go traffic for 20 mins then went into walmart for 20 mins then top and go traffic for another 20 mins.
Then I got on the highway doing 70-80mph for around 15 mins with stop and go traffic for 10 minutes. During this time I could hear the whine when accelerating. Drove the rest of the way home going anywhere between 45 and 60 (non interstate) for about 50 mins. Could only hear the whine when i got off the interstate if i was going faster than 40mph.

I've drove it twice since (15 minute drives) not going over 60 and i no longer hear it. I work tomorrow and thats when I do alot of driving so im worried about it.

I checked the CVT fluid its kinda black at the bottom, but is black clear towards the top I ran it through my fingers and felt two hard pieces the first time, I did it two more times and felt nothing, and its above the top hash mark COLD, and when heated up its super high.

I already plan on doing a CVT drain and fill, but I want to know if there is any aftermarket coolers that will work for my Sentra. Ive spent the whole weekend searching, and i cant find anything.

I also want to know if you guys think my transmission is screwed? It doesnt shift hard or anything, but it does lurch a little when i changed the gear from like park to drive or reverse etc. This is my first automatic so idk if this is normal. I've always drove manuals.

I just spent all my savings on this, and my internship ends really soon and school starts again. All my saving was suppose to pay for books and gas and insurance now I probably wont be able to so getting the transmission replaced isnt an option

Welcome to NICO!

First and foremost, you cannot use color as a guide to determine if the CVT fluid is bad or not.

Second, you'll find a lot of useful info in these threads:
Concerns about CVT Trans
CVT: Fluid Check
CVT: Fluid Change
CVT: Fluid Change 2
"Rattling noise in CVT"
Nissan Gives 10-Year CVT Warranty to All Vehicles?

Well, you said it is black to the bottom and you found particles that you could actually feel? I read some of the other information posted regarding fluid color and nissan having some algorithm to measure the fluid, BUT, they also said that the fluid should be light amber. In my opinion,if you have black fluid, then you have an amount of contamination that should not be taken lightly, specially if you could actually feel the particles when you touched the fluid. Nissan extended warranty afaik is 10 years or 120k. Nothing is going to take those particles and pieces of metals out of the transmission if you dont do a proper fluid change. That would be your best bet and then just hope that it last enough for you to finish your internship. Otherwise sell it and avoid vehicles with CVT's.