My tranny builder and I are going to try something different but the car will throw a code and prolly go to fail safe mode, I know the computer will have the car shifted to 3rd but what else does the computer do to the car. Does it mess with any fuel tables or and other kind of engine tables? Does it mess with anything other than the tranny? I am thinking of turning my Vaccum 4L60E into a Lenco 4L60E.
Is this something a tuner can take care of, I have a speed density tune with a local speedshop

 

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you might get better results if you post this in the tuning section

 

Its already over there

 

hmmm...well since your running speed density, i'm not sure it will do anything. Typically on a maf tune it will fatten up, pull timing and read from a set of VERY conservative fuel tables. Going to a vaccuum modulated tranny is common and can be done. i think you will need to do something to torque management to get it to work. There are guys running th400 and th350 with full manual valve bodies, so I know it will work.