85 s10 Chevy blazer: back window and tailgate won't open

the outside latch and other parts https://www.google.com/search?q=1989+chevy+blazer+s10+tailgate+latch+assembly&rlz=1C1CHBF_enUS812US812&source=univ&tbm=shop&tbo=u&sa=X&ved=0ahUKEwjnvKX9tu_iAhVth-AKHYMBCpcQsxgILw&biw=1600&bih=789 https://www.youtube.com/watch?v=E0yC1-EhjSI

sound you have a blown clutch slave cylinder

there's a plastic actuator inside the tailgate that probably broke or at least came loose. You have to crawl into the back and release it. I ended up having to cut a little piece of carpet in the middle on the top of the tailgate area. Right where it fastens. You can manually release the glass with a screwdriver at that point. To replace the actuator, you need to take off the entire tailgate trim and metal underneath that to get to it. It sounds like a pain but trust me, not having the back glass be able to open or the tailgate area is much worse. It takes about 45 minutes to fix. The actuators are less than $10

http://www.carforum.net/general-auto-repair/7310-2003-chevy-blazer-door-lock-rear-window.html

I don't know what wrong with your tailgate but your engine is a 4.3 liter

This is how to replace it on a 1996 Blazer 4dr.

First, go buy the part you need at Rockauto. The link is for a 1996, but make sure you order it for your vehicle. Just do a search for a Window Actuator Rod Retainer. Rock Auto requires you order a pair of these, so make sure you order two. Each one has two of them in there so you will have 3 extras.
Window Actuator Rod Retainers - RockAuto.com

To open the window in the mean time while you are waiting for the part, do the following.
1. Remove the two screws on the door handle so you can pull back the door panel.
2. Pull back panel on top in the middle where it rises.
3. Reach in with a screw driver or your fingers to push down the lever. It's a metal piece on the left side against the wall to the inside of the blazer.
4. Open window and tailgate and remove screws on the sides of the tailgate. There is one on each side. Make sure it is the one fartest out and on the plastic panel.
5. Once the screws are removed, pull up on half the panel that is farthest out from the truck. Slide out away from the truck. The panel should come off with a little effort. Do not pull up on the panel closest to the truck, you will break the hooks that hold it in. I broke two on mine. The panel will slide away from the truck pretty easily.
6. Remove the screws holding the middle metal panel down. There are about 12 screws. They are the 9/32 socket screws.
7. Pull the metal panel up, first dislodge the metal poles connected to the two white clips on each side in the center of the panel.
8. You will now see your actuator with the broken blue clip.
9. Pop off the blue retainer from the actuator. This will take some effort but it will pop off. (here's where you can replace the actuator if it's not making a sound)
10. Place one end of the retainer into the loose metal piece that rotates (left arrow in third picture) and then pop the other end back on to the actuator.
11. Replace the metal panel and clip the poles back into the white clips.
12. Make sure your door handle rod is clipped into the lock before you close the tailgate. If not, you have to work at opening it again by sliding you arm down between the plastic panel and it's not easy.
13. Replace everything. Before you close the door, make sure the door handle works and make sure the actuator is connected.
14. You should now be able to use your tailgate window again!

I am taking a guess your trying to remove the tailgate panel to fix this problem???

under the carpet installed on the tailgate door, there is a hole. put a screw driver in it and manually flip the latch open, to start.
yjen take the door panel off, one screw with the interiro handle, and pull the rest off,
watch the auto release slidw side to side, you will find a broken piece here, I made an extension piece with a plastic hook and screw, works fine for over a year, lube all latch parts with wd 30 once opened.

there is a motor inside tailgate that is probably weak and doesnt have enough to engage the unlock mechanism

open the door panel do a visual of the window transmission there may be some object blocking free travel of the window

IF YOU get in the back the panel will have a slot behind the carpet this will be in center right at top of carpet area on plastic panel pull carpet back and you can slide a screwdriver in there and move actuator to open