Background: Last week on my way to class, driving in top gear I noticed by car start to lurch/buck/jerk forward in intervals, then the dreaded up arrow started blinking. Parked and when leaving school, the up arrow didn't return but the check engine came on instead. Drove home and cleaned the PNP switch. Check engine was still on, so I used the OBD1 to check the code, and got 114, 323, and 322. I read on a forum post of someone changing the tranny fluid and the car ran fine after. Also, some considerations. The car's at 198,487 miles, and in the past 3 years the transmission fluid has been "changed" only once, partially, a year and a half ago when I pulled the axles and some drained out. My dad told me it's best not to change the fluid because of the gunk and such and so I never did.

So, this morning I drained 3qt of the old fluid and replaced. Car shifted silky smooth, but after 2 min in top gear, the car was lurching. Then moving from neutral to reverse gave a heavy clunk like before. While cleaning up waiting for a few more miles to do the next change (as per RobertDIY's instructions) I noticed coolant droplets in my catch pan. My radiator's only a year old, so I wouldn't think that's it. I drove through some deep water a few months back but this wasn't clear water, it was clearly green coolant.

All this to say, I'm not sure if it's slipping because the fluid is bad and/or because the clutch plate is deteriorated from this coolant being in here for God knows how long. It isn't a ton of coolant, but I don't know how much that matters. Is the deterioration causing the slip rather than something like a clogged solenoid or old fluid? Any suggestions on where to go from here?

 

the way coolant can get in the tranny is via the transmission cooler that is part of the radiator. you'd want to fix the radiator/trans cooler first then do a full transmission flush (not a drain fill). On the 850s you can do a transmission flush by using the lines that go to the transmission cooler - one line will act as a sump the other as a drain. I bet there's a youtube vid for the process but the general idea is attach some clear hose to the lines then stick one in a bucket with fresh clean Dex 3 and another bucket for the old fluid. Start the car to allow the transmission to pump in the fresh fluid and push out the old stuff. Keep going until you see clean red fluid on the output side. Figure this will take a 12 quart case of fluid.

 

I saw that method on another forum and was considering doing that from the get-go, but decided on the drain and fill was a little easier. Is it possible the flush alone could fix the slipping? I figured the clutch was damaged and couldn't be fixed without a rebuild, or it this just a shot in the dark because it's cheaper than a new transmission.

 

I wouldn't be too optimistic, but I guess people generally clean the mess up because it's cheap and maybe you'd do it if there's a 1% chance it works.