u/FunRaise6773

I have a 2014 econoline e350 with the 4r75w transmission. The van has 170k on the odometer, with a rebuild tag on the transmission, indicating that the unit has something less than that on it. Thumbing through service history, the fluid was changed at 100k miles, 50k less than the recommended interval. Today, it lost 3rd gear. 1/2 shifts fine, but it delays going into 3rd, then free spins with no acceleration. Manually shifting back to 2 restores acceleration. Fluid is normal in color, but was about 1 quart low. I added the quart with no change. There’s no codes using forscan either. What suggestions are out there for further troubleshooting, or am I straight up looking at a teardown and rebuild?