Having issues with input values not matching output

[DoghouseDiesel]

Doghouse, thanks for the info. Since your first post I have been reading on this and starting to grasp it a little. For example, if I have the 3-4 shift set at 54 and it shifts at 49mph then my GP could be rising too fast and I need to back off on the governor pressure so it does not rise quickly enough to cause a shift at that point which happens to be the 49 I am seeing. Does that make sense?

Correct. Just be careful with the GP. Make SMALL changes at a time.

[cumminsDK]

It is. A PCS standalone and a full solenoid valve body have been on my mind for awhile.

So glad you mentioned this, wondered if such a thing existed. I love the drivability of an allison. How much would this setup cost?

[icemanjc1]

$1900-$2600 depending on the company.

[dsltnr]

That's exactly what he's running into, but the reason he's not seeing changes is he's not adjusting THE most important variables with regard to the transmission, governor pressure and TTVA angle.

Just as an example here, I'll break this down in a mechanical manner.

If you take an early 48 (03-04) that doesn't have the TTVA, but is still linked mechanically to the throttle by the TV (throttle valve) cable, you can vary shift points simply by adjusting the detent on the cable. Increasing or decreasing this adjustment moves shift points up or down by approx 75 RPM's with each 1/8" of adjustment. This is is what you now do with the TTVA. This will have the biggest impact on wide open throttle shifting.

Now, lets look at governor pressure. On a stock VB, governor pressure rise is relative to speed and there are a few key pressures that must be obtained to cause an up or down shift. 1st gear is normally 0-28 psi, 2nd gear is normally 29-58 psi, 3rd gear is normally 59-95 psi, and 4th gear and TC lock occur at 95-128 psi. This is where you you make adjustments in your part throttle shifts.

The other thing you need to look at is the relationship between Governor Pressure and TTVA angle. The more TTVA that is applied, the higher the shift will occur, as it thinks you're deeper into the throttle and this applies pressure to the back side of the shift valves.

Do you see how much I've referenced those shaft speed and throttle percentage tables yet? Not much, right? That's because those will really only effect 3-4 up/down shift and the TCC solenoid. But, they are the least important in the shift scheduling.

This is why whenever you have shuttle shifting, delayed shifts, harsh engagements, etc., it usually an indication that you have a problem with the governor solenoid or gov solenoid pressure sensor.

Doghouse,

this statement from you has caused me a little bit of confusion.

"On a stock VB, governor pressure rise is relative to speed and there are a few key pressures that must be obtained to cause an up or down shift. 1st gear is normally 0-28 psi, 2nd gear is normally 29-58 psi, 3rd gear is normally 59-95 psi, and 4th gear and TC lock occur at 95-128 psi. This is where you you make adjustments in your part throttle shifts."

You reference 4th gear shift with the governor pressure, yet the ATSG manual says multiple times:

"The overdrive solenoid is used only to engage the gear change from 3rd to 4th gear"
"The Governor pressure solenoid is used for upshifts and downshifts for 1st, 2nd and 3rd gear ONLY. The 3-4 shift is controlled by the overdrive solenoid on the valve body"
"Governor pressure is controlled electronically for 1st, 2nd and 3rd gear operation ONLY. The 3-4 shift is controlled strictly by the OD solenoid."

Based on the ATSG manual, the Governor pressure table has nothing to do with the 3-4 shift.....? So earlier when I made the post in reference to the above statement saying that I had the 3-4 shift TABLE set at 53 mph but it was shifting at 49 mph, I assumed that my governor pressure was rising too fast and creating the 3-4 shift at 49 mph. As a result, I needed to drop pressure in Governor pressure table to hold out the 3-4 shift longer and you agreed. Based on the manual this is not true and will not do anything for the 3-4 shift.

Did I miss something? This information in the manual has thrown another monkey wrench in the mix with that info unless I misunderstood it.

[dsltnr]

This also makes sense in the tuning tables. You dont have a 1-2 and 2-3 and 2-1 and 3-2 table like you do for 3-4 and 4-3. Reason being, (looks like to me) is because of the info above, the 3-4 has nothing to do with the gov press table and that is why it has its own table while the 1-2 and 2-3 can be controlled by Gov Press and TTVA tables. (Thinking out loud)

I always found it odd there were no 1-2 and 2-3 shift tables and this could be the explanation.

So, I am back at square one trying to control the 3-4 shift. I tell the table where to shift but it will not yet the manual says the Gov Press table has nothing to do with the 3-4 shift so if the 3-4 table will not control the 3-4 shift and the Gov Press table will not control the 3-4 shift then I guess...well I dont know what I guess really...lol

[DoghouseDiesel]

Data log what is happening and see what it does at the 3-4 shift and TCC lock-up.

You'll see what happens with GP.

While the solenoids control the ACTUAL application of the shift and lock-up, there is another condition that must be met.

You need to understand the values that the ECM uses to COMMAND those solenoids to act. Something has to TELL those solenoids to act, right? What is it? Does it just happen automatically or does something have to TELL the solenoid that NOW is the time to act. What tells it to act? What does the ECM see that tells it NOW is the time?

[dsltnr]

Data log what is happening and see what it does at the 3-4 shift and TCC lock-up.

You'll see what happens with GP.

While the solenoids control the ACTUAL application of the shift and lock-up, there is another condition that must be met.

You need to understand the values that the ECM uses to COMMAND those solenoids to act. Something has to TELL those solenoids to act, right? What is it? Does it just happen automatically or does something have to TELL the solenoid that NOW is the time to act. What tells it to act? What does the ECM see that tells it NOW is the time?

I have about 50 datalogs to look at...lol and I think I see what you are referring to. One thing I noticed this morning while comparing actual GP table to datalog results is I have an issue with my speedometer that may be causing alot of my headache. I am about 3-4 mph off and I am correlating alot of issues that are about 4 mph off.

I have 275/65/20's and that should be 34.21" which is 592 revs per mile. However, I enter this info in EFI software and load it and my speedometer is still around 4mph off and I think alot of my calculations are off due to this. Watching the datalog and comparing Governor pressures at certain shaft speeds and mph, the datalog does not match the table and it is about...4mph off...hmm.
I have got to get the speedometer calibrated properly first before I continue and it will not cooperate. Until then I think I am wasting my time.
You ever use any aftermarket devices to do this? Is there anything available for this. I ask because the software is having no affect on it by altering revs per mile under the Misc. Tab. I think FUBAR was having this issue also?

[DoghouseDiesel]

Just takes time.

Tuning the transmission, with the archaic setup that a 48 is, is worse than tuning the motor.

It's much easier when your VB is setup mechanically to make it do what you want in the first place. Tuning a stock VB takes a lot more time.

[dsltnr]

Are these PIDS the Governor Pressure that will show you the Gov Press table data or is this a different pressure other than the Gov Pressure? I am referring to the two in the table attached named
Transmission pressure actual and commanded

In the stock table they max at about 875 kpa which is around 126 psi. Just want to confirm what pressure these two PIDS are displaying.