[secondarychaos]

Hey folks,
what do you change in the tuning (if anything) for a shift kit or valve body?
Is it worth getting one or should I just change line pressures further in the tuning?
Dan

[Power Hungry]

In general, we remove all shift pressure modifications and let the tranny do its thing.

Is it worth it? Yep. The changes in the valve body will allow fluid to flow easier without having to "push" it through the smaller orifices. This allows for much smoother and firmer shifts. Definitely worth the cabbage.

[secondarychaos]

thanks Bill.

[kokopellimotorsports]

I just ordered a valve body for my '05. So it is good to hear, Bill.

Ty

[secondarychaos]

Follow Up question: the line pressure modifications come in the TV slope category and TV pressure offset, right? are there any others that I need to change?

[Power Hungry]

TV Slope and Offset are used to modify holding pressure. You also have TV Pressure on shifts (1-2, 2-3, and 3-4) to modify these pressures up or down for shifting.

Hope this helps.

[soutthpaw]

I have a follow-up question too.
1. What do increased line pressures do ? (i thinking more hold force against slippage under high HP conditions)


2. What are the optimum and/or safe line pressures we should be using?


3. I did the transgo shift kit in my tranny but didn't install the new pump valve and spring because I didn't want to take tranny out... can I tune to duplicate what that pump pressure spring does? If and when I do a TC upgrade.

4. Which settings control how hard and which control how fast the trans shifts?

[Power Hungry]

#1 depends on whether you're talking about main line pressure (EPC), gear holding pressure, or shifting pressure. Many early transmission strategies reduce pressure during shifts to prevent harsh shifting. Later strategies will often raise pressure during shifts because these calibrations include torque reduction strategies to reduce engine output during shifting.

Outside of that, increased TV pressure will apply more pressure to the clutches and result in more holding pressure. The downside is that increasing pressure will increase fluid temperature and also robs a little power from the engine. On diesels this loss is marginal, but on a gasser it can show up most notably as as lost fuel economy.

#2 is difficult to answer because it depends on several factors including load, throttle position, rate of acceleration, transmission fluid temp., and others.

#3 is attainable by increasing desired EPC in the calibrations.

#4 uses shift pressure modifiers (TV Adder, Slope and Offset) to control how hard the shifts are and shift delay to control how fast shifts occur.

One thing to keep in mind is that most shifting functions are controlled by tables that use an estimated torque output to handle things like pressure and delay. Most of the shift modifications can be handled by changing these values alone so they accurately reflect the amount of power the engine is producing. The other tables and functions are for fine tuning.

Take care.

[soutthpaw]

Thanks for the reply, Learn something new everyday