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Help me get pick out trans modifications

3K views 5 replies 4 participants last post by  Beach Goat 
#1 ·
I know almost nothing about automatic transmissions, compared to manuals and general engine knowledge. So I could use some help here.

2006 Daytona 5.7L, 6.1 heads, Spartan+ cam. Not too rowdy, but with the big heads on stock displacement the driving manners aren't great. I even installed 3.91s to try to help the engine get some rpm and piston speed faster, and it helped (definitely more fun to drive).

Basically the car pushes through the brake pedal unless applied pretty firmly. Engine will occasionally buck at very light throttle. Engine will maintain speed even off throttle unless over about 30mph.

On a WOT downshift from second to first, sometimes the engine will over rev, shift is set to 6k but it will rev to 6400 before shifting. I used to have the shift point at 6500 but it wouldn't shift until nearly 7k and would hit the trans limiter and go into limp mode. This happened on WOT downshifts and whenever the car spun the tires in first.

The speed parts were installed and tuned by Brent at Dyno Tuned Performance. Since then I've tried every small adjustment in the Diablosport that I can to get the car's manners in check, and I have it as good as I can get. Throttle boost can't be put amy higher or lower or the car won't idle right at cold start. Idle rpm is set as low as possible (roughly 850rpm) or the car will die on start up. Idle is set to raise 50rpm in park, otherwise throwing it into park will make the idle drop and almost die. Shift points are at 6k but the cam is making power above that so I'm losing acceleration :/

I believe I need a stall and a TCM. I've kind of explored a little bit about these items but I'm kind of in the dark, I've never modified an automatic.

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#2 ·
I have a 5.7 with inertia heads, inertia cam and a d1sc procharger. Mine acted the same way when shifting. I also have 3.91 gears. I put in a 3200 fti stall, dings racing valve body and a tuned tcm. Now it shifts perfect, no more limp mode either. It was well worth it.

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#4 ·
Stock throttle body and injectors?
 
#5 · (Edited)
I would need to see a dyno graph to accurately tell you what stall speed converter to go with. A general rule is you want the stall speed to be very near the rpm where your car makes the most torque. They also assist in the idle mannerisms of a big cam. That would be my first mod.

Then I would buy a valve body. Should be all you need unless the internals of the trans are going.

You say “one day”. Is that soon or years away? If soon, hold off on the converter, you will likely need to reswap it out for optimal performance.

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