P0780

P0780 is a TCM-detected general shift malfunction — the TCM commanded a gear change, watched the input/output shaft speed ratio NOT change to the new gear's expected ratio within the allowed time window (typically 0.5-1.5 seconds), and threw the code. It's the umbrella code that fires alongside or instead of the gear-specific P0781-P0785 family. Cheapest-first ladder: (1) Pull all trans codes and look at the company P0780 keeps — a lone P0780 with no shift-specific codes usually points at TCM software, ground, or input data; P0780 paired with P0741 (TCC stuck off), P0700, or any solenoid electrical code is pointing at the solenoid pack. (2) Check fluid level and condition first — low fluid is the #1 cause of slipped shifts that throw P0780 on every transmission ever built, and burned/dark/varnished fluid means internal damage that no solenoid swap will fix. (3) Scan-tool live data and command a 1-2, 2-3, 3-4 shift while watching commanded gear vs. actual gear ratio (input RPM / output RPM should land at a known value for each gear: roughly 2.4:1 in first on a 4L60E, 1.4:1 in second, 1.0:1 in third, 0.7:1 in fourth); the gear that doesn't land at the right ratio is the gear that's failing, which converts P0780 into a specific P078X you can chase. (4) Inspect the trans pan magnet for metal — bronze flakes mean bushing wear, steel flakes mean planet/sun/clutch debris, and either rules out a cheap fix. The expensive-misdiagnosis caveat: P0780 with clean fluid and normal cruise behavior is often just a sticking shift solenoid ($90-250 parts, half-day labor); P0780 with burned fluid, slipping under load, or a delay-into-gear is internal damage and the rebuild ticket starts at $2,500.

Vehicle-specific patterns: 1995-2014 GM 4L60E (Silverado, Tahoe, Trailblazer) throws P0780 most commonly from the sun-shell crack/split — the reaction sun shell breaks at the splines and causes intermittent reverse loss along with random forward-shift faults; a hardened replacement sun shell is $80-150 part, but it's a pan-down or unit-out repair depending on access. 1996-2008 Ford 5R55E / 5R55W / 5R55S (Explorer, Mountaineer, Mustang) is famously a P0780 generator — the intermediate and overdrive bands wear out around 100-150k miles and shifts go long, soft, or missing entirely; rebuild on these is $2,200-3,800 because of the band-and-servo complexity. 2003-2012 Chrysler 545RFE / 65RFE (RAM, Durango, Grand Cherokee) throws P0780 from the TCM solenoid pack ($200-400 part) and from worn input/intermediate clutches around 130k miles. 2013-present Aisin AS69RC (RAM 2500/3500 HD diesel) throws P0780 from internal valve-body wear and is a $4,500-7,000 rebuild given the part costs. Estimated repair: $250 (solenoid pack) to $7,000 (AS69RC rebuild).