P0735

P0735 sets when the TCM commands 5th gear and the calculated ratio is outside the expected 5th-gear window (typical 0.71-0.75:1 on a 5-speed overdrive, varies on 6-8 speeds where 5th may be near direct) by 5-7% for the dwell threshold. On most 5-speed-and-up modern transmissions, 5th gear involves a specific clutch pack or a combination of two apply elements working together, so a P0735 can be caused by any apply element failing or any solenoid commanding the wrong element. Cheapest-first ladder: ATF level and condition at spec temperature, line pressure across throttle range under load, scan-tool ratio monitor during a 4-5 upshift on a road test (the ratio should drop cleanly, a flare or slow settling indicates slip), and solenoid resistance checks at the case connector against the trans-specific spec sheet (typical 10-25 ohms for on/off, 4-7 ohms for PWM, infinite ohms is open, under spec is shorted winding). Verify the TCM is commanding 5th and not bouncing between 4th and 5th, hunting in the shift command itself can throw P0735 even with a healthy mechanical 5th. Expensive misdiagnosis: do not authorize a teardown without first verifying that the trans actually slipped, an erroneous output-speed-sensor reading produces a phantom P0735 with a perfectly healthy mechanical 5th gear, replace the output speed sensor or repair its harness first because that is a $40-150 fix versus a $2,500-4,500 rebuild.

Vehicle-specific patterns: 2004-2010 Toyota Sienna/Avalon/Highlander with U151E 5-speed sees P0735 from B3 brake apply failure tied to valve-body solenoid wear, sonnax valve-body kits address the root cause; 2005-2010 Nissan Frontier/Pathfinder 5AT (RE5R05A) has a known 5th-gear apply issue from accumulator and solenoid B wear, Nissan TSB NTB07-077 covers the diagnostic; 2007-2013 Hyundai Santa Fe/Sonata with A6LF1/A6MF1 6-speed throws P0735 when the 26 clutch pack wears, the trans is often replaced as a remanufactured unit rather than rebuilt because parts availability is limited. Estimated repair: $300 to $4,800.