LBZ transmission tuning

[athoma94]

have a truck with a suncoast built trans 1056 convertor with gmax kit owner complaint is that they would like to have firmer shifts. I haven't really done much with transmission tuning looking for a little advice on the best way to help him out. thanks in advance

[S Phinney]

Are you meaning firmer or less defuel?

[THEFERMANATOR]

Shift feel cannot be tuned other than the amount of defuel the ECM gives during shifts. Reducing defuel is NOT reccomended if you want the trans to live though. I played with it a little, and it was a costly venture. Shift feel is controlled with how the trans is built. The ALLISON prior to 2011 is mechanically controlled trans as far as pressure goes for the most part. Stock line pressure is 240 PSI, and it drops 100 when in lockup to give you 140 psi in lockup. The trim circuits are limited to 125 psi with stock trim valves. When built the TRANSGO trim valves give full line pressure to the trimmed circuits, the basic pressure shim should give you around 270 line pressure, and knock down is dependant on wether they used a TRANSGO valve, stock valve, or eliminated knock down all together. Theres also the new MIKE L trim springs to give faster pressure rise on shifts to help shift firmness and feel(faster shifts), the MIKE L pressure spring kit that will maintain the increased line pressure over time where as the stock one with a shim will lose pressure over time, and some other internal mods that can be done during building of the trans. As far as tuning goes though, I would be VERY leary of reccomending ANY changes to shift timing to try and make it shift faster/firmer. It's best to make the chnages internally to work instead of electronically IMHO.