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Thread: Locked vs unlocked converter during shifts (6L80E)

  1. #1

    Locked vs unlocked converter during shifts (6L80E)

    Is it bad on the transmission clutches to downshift with a locked converter at part throttle or should it unlock, downshift and then relock in the next lower gear? I'm working on the trans tune in my truck (turbo 5.3, 5000lb, 3000 or so triple disc, 6l80e) and I'm trying to figure out what's best for the trans yet comfortable to drive. When trying to pass someone on the highway, I'd like for it to downshift to the next gear for the extra torque yet I don't want to have to unlock the converter and have it flare up to 3000 rpm. What's the common method here guys?

  2. #2
    Advanced Tuner
    Join Date
    Jan 2014
    Location
    Waldorf MD
    Posts
    774
    Yes you can hurt the trans trying to downshift locked. I just had mine unlock at a certain throttle input. Didnt downshift and the stall "flare" allowed me to pass with ease. Now if I smashed the pedal, all bets were off. Unlock and downshift.
    Daily Driver= 2003 BMW 330xi
    Weekend Cruiser= 2009 Pontiac G8 GT (Vararam, TSP LS3 N/A Stage 1, OBX, CTS-V converter, MagnaFlows w/ J-Pipes, 160 t-stat)
    Project Car= 1991 Chevrolet Camaro RS (LQ4 w/ Gen 4 Rods, LS3 heads, turbo...)
    Truck= 2007 Chevy Silverado 1500 LT LY5 4x4

  3. #3
    Advanced Tuner
    Join Date
    Aug 2010
    Location
    Detroit, MI
    Posts
    926
    Err on the side of caution, especially if you're unsure of what you're doing... It is possible to shift with a locked converter, but everything needs to be calibrated properly in order to perform a torque handoff from an offgoing clutch to an oncoming clutch. That includes calibrating slow and fast path engine torque from the transmission's torque management requests as well. I 'tooned' an Ecoboost Raptor a few months ago and that 10 speed stays locked up almost constantly. Ford has that trans dialed in.