15 mirage engine and transmission swap for 19

[Fummins]

I have not had a very good look at the engine or trans yet besides checking fluids, it was hit from the passenger side front and it completely crushed the frame on that side, from the looks of it the trans should be fine but I will be checking it out on the weekend, will know for sure then. From your experience is the valve body typically what goes wrong? I have been having surging, slipping, bucking for around 80k but now its starting to get dangerous, most recently it has been accompanied by a screech like noise sounding very much like a belt. No blinking D yet but almost positive it going to start soon.

Changing the valve body won't fix every cvt issue but can fix some. Most of the failures I've seen were a thrust washer failure, as seen in the second teardown vijeo. Those ones were screwed. The fluid turned black almost imediately after replacing it, the engine would want to stall when stopped and in drive. The only way to know if that's your problem is to drop the oil pan and look for pieces of the bearing.
I have had one cvt act up at around 186000miles. It wouldn't rev up, and was throwing cvt codes(flashing shift indicator). I replaced the valve body with a used one(after removing pieces of piled up bearing from it) and it's now got the same mileage as yours.
Someone commented in one of the cvt teardown vijeo's that they replaced a valve body for a customers cvt with high mileage that was surging and it fixed it. The one in my own car was surging fairly often, I was replacing the engine anyways(spun rod bearing) and picked up a basically new cvt and threw it in. After tearing the old one apart I'm pretty sure I could have just thrown a valve body at it and been good for another 100k miles. But I didn't want it to crap out a month down the road so I just replaced it.
I don't know what I'd do, maybe just replace both at the same time if you don't want to waste time experimenting.

Not a mechanic but one would assume just swapping the tranny would be less work - especially if your engine is fine. I'd definitely keep the parts car for later use, though

Yes and no. Mirage transmissions aren't hard to replace with a hoist but it'd be a bit of a pita to do with the car up on jack stands. The hardest part would be trying to wrestle it in and out of place unless you have a decent adjustable transmission jack that pivots. It's easier with the subframe removed but then you have to get the rack an pinion lined back up to the steering column because the shaft isn't keyed. And...you have to support the engine with the transmission removed.
There is more stuff to remove when pulling the engine with the transmission but it's easier to bolt them together when they're not in the car.

[Fummins]

I just looked back at records of the highest mileage 2017 Mirage in the fleet. There was a complaint about surging at 60-70mpg one year ago, almost to the day when the car had 243k miles. Records show I removed, dismantled, cleaned, and re-installed valve body and it's been good for the last 68k miles. Oddly enough, the filter replacements that may or may not have been done on this particular cvt kinda goes against what I and the internet experts recommend.

[Ddmrcsen22]

I just looked back at records of the highest mileage 2017 Mirage in the fleet. There was a complaint about surging at 60-70mpg one year ago, almost to the day when the car had 243k miles. Records show I removed, dismantled, cleaned, and re-installed valve body and it's been good for the last 68k miles. Oddly enough, the filter replacements that may or may not have been done on this particular cvt kinda goes against what I and the internet experts recommend.

I think I’m going to experiment and swap the valve body. I’m very interested in seeing if it will work and also seeing how far I can take the factory drivetrain before it actually craps out. Longevity is my goal.

[Ddmrcsen22]

Not a mechanic but one would assume just swapping the tranny would be less work - especially if your engine is fine. I'd definitely keep the parts car for later use, though.

FWIW, if it makes you feel better, I got my MT swapped out for a lower-milege one at 75k and cost some $1500, new clutch included. I know I was ripped off, but it was what it was. Since then, I've taken (better) care of the tranny and now at 125k with no issues (yet).

What repairs or maintenance have you done at that mileage? Are you the first owner?

Congrats on such a high-mileage! Nice to know the mirage does well up there.

Not the first owner it had just over 100k on it when I bought it with a salvage title, busted windows caved in doors destroyed interior, slowly pieced it back together. Was poorly maintained and I’ve kept up on everything possible, only thing I have done is keep the oil and tranny fluid changed. Spark plugs, Wheel bearings, brakes an alternator and a starter. Been a truly reliable machine despite it having a rough life. Questioned it being worth it a some time ago now but it has been money well spent.

[7milesout]

I think I’m going to experiment and swap the valve body. I’m very interested in seeing if it will work and also seeing how far I can take the factory drivetrain before it actually craps out. Longevity is my goal.

Ok, I can respect that mindset. Please keep us posted on your results.