Having issues with input values not matching output

[dsltnr]

I have been working with the trans tables alot lately and either there are overriding parameters hidden that we have no control over that dictate results that are contradictory to the tables you input values into or input values on some tables mean nothing and you have no control in the end.

I will start with just a couple of examples.

If you look at the tables for my 3-4 shift in tow haul mode, I have done a test tune and set up the 3-4 upshift in tow haul at around 55 mph (these values are only for evaluation purposes)
Based on the conversion calculator the TOS OUTPUT SHAFT speed for this is around say 2200. So you can go in and set the axis define on teh 3-4 upshift in tow haul mode to
2200 2210 220 2230 2400, etc etc
set the 0% pedal at 2200 and 10% at 2210 and 45% to 2220 adn 55% to 2230.

Bases on the numbers above I am saying if the pedal is between 0% up to 55% shift between 2200 and 2230 which should be around 55 mph. It will shift at 49 mph no matter what I set it to. I can set it to 5000 rpms for shaft speed and anything between and it will shift at 49 mph EVERYTIME. Regardless of mph it will shift at around 1975 to 2000 shaft speed no matter what which is 49-50 mph. So, no matter what the table says it shifts at a constant point everytime.

Tq converter unlock in 3rd gear in tow haul will unlock at 20 mph no matter what and I have no clue where it arrived at that number? That is actually too low and almost starts lugging the engine. Regardless of what the table says it has no bearing on where it unlocks and I dont know where it is getting reference for what is doing?


I could go on and on on multiple tables where the input values have no bearing on the results. Now before you start with this table references this table references this table deal like with the engine, we are not talking about the engine. We are talking about a 3-4 shift table that is supposed to control the 3-4 shift location. How many tables can control the 3-4 shift location and if there are more than one then what was the purpose of giving us control to a a table that requires other tables input that we cannot see? That is not meant to be sarcastic, just trying to understand if I have an issue with my software, my truck or pcm or what because there are certain things that do what they want but then again there are many others that work flawlessly.

Can someone out there go to tow haul mode and change the axis define to
0=2200, 10%=2210, 45%=2220, 55%=2230, (set the rest to whatever, not important for this discussion)
Then go out and datalog and tell me what TOS you shift at while holding the pedal at around 40-45%. What I am getting at is this, if you set the numbers I just listed, do you shift at those numbers?

Here is another good one. I took all the tow haul tables and set them up the same in the NON tow haul tables and it is nothing like each other. Two totally different animals. Once again, is there tables that override these values that I cannot see or do not have control over? This makes no sense to me. So the tow haul modes will do one thing up to a certain value but the non tow haul will not yet they look the same? The same values from the tow haul tables inputted into the non tow haul tables gives you a totally different result? This cannot be right.

Any help from anyone is appreciated.

[DoghouseDiesel]

I think we spoke this past weekend, right?

Did you try what I told you? Governor pressure and TTVA?

1-3 is completely dependent on governor pressure and TTVA. 4th and TC lock are solenoid controlled, but also dependent on gov pressure. If you haven't adjusted those, you won't see a change.

Like the rest of the things that interact together on these truck, just changing one parameter doesn't always give you the intended result.

Also, who's VB are you using? A stock one or aftermarket?

[dsltnr]

I think we spoke this past weekend, right?

Did you try what I told you? Governor pressure and TTVA?

1-3 is completely dependent on governor pressure and TTVA. 4th and TC lock are solenoid controlled, but also dependent on gov pressure. If you haven't adjusted those, you won't see a change.

Like the rest of the things that interact together on these truck, just changing one parameter doesn't always give you the intended result.

Also, who's VB are you using? A stock one or aftermarket?

Yes we did talk and thank you for your time. You are always giving time to answer posts and calls and for that I say thanks.

Ok, on to the issues. I am not trying to be argumentative just totally understand. I am not the type of person that simply wants to know what to do, I want to understand why so that can be good and bad.

First, the valve body is totally stock. I want to totally get all I can get out of a stock truck before moving on.

Sounds like I need to take a crash course and learn completely how the TTVA and Governor pressure solenoid works. Any suggestions on who or where I can learn this. I am willing to pay for the knowledge if necessary.

You are saying by changing the 3-4 shift table, it means nothing unless you alter the TTVA and Governor pressure tables? Why have a 3-4 table? I mean lets look at this conversely, if I leave the 3-4 shift table alone and only change the TTVA and GP tables, then is the 3-4 table useless if I can do all the shifting locations with the TTVA and GP tables?

Why can I take all the tow haul settings and copy them into the non tow haul tables and get a totally different result. This has nothing to do with the TTVA and GP tables if they are exactly the same in both..?

Or, is everything in the trans dependent upon the TTVA and GP tables and if so, why is there no reference to what gear you are in within the TTVA and GP tables just TOS rpm and that is dependent upon the ratio of what gear you are in? Just thinking out loud here.

What I am trying to say is something as simple as a 3-4 shift table becomes useless if I am understanding you and I need to be changing nothing but the TTVA and GP tables?

On the stock set up the GP tables have less pressure in the full throttle tables than they do in the normal throttle tables?

I just assumed you take a 3-4 shift table and tell it where you want it to shift and that is that. Instead it sounds like to get the trans to shift where you want it, you have to alter TTVA, GP and a 3-4 table and hope they line up? Wow.

Ok then I will go with it. Where do I start in learning and understanding the TTVA and Governor Pressure functions. Any good reading out there or anyone want to offer their knowledge for a price?

[DoghouseDiesel]

You really need to understand the functions of the valve body to make use if those adjustments.

VERY small changes make a big impact on how the trans responds.

You need to know what pressures cause a shift to occur and how the TTVA angle can delay or advance a shift.

What you might want to do is pick up an ATSG manual and learn how the valve body works and what conditions cause shift conditions to be met.

[skneeland]

I know there have been issues with changing axis table values not actually doing anything, particularly in the transmission tables. I dont know if this has been addressed in the recent versions or not, but something to ponder.....

[DoghouseDiesel]

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.

[dsltnr]

I know there have been issues with changing axis table values not actually doing anything, particularly in the transmission tables. I dont know if this has been addressed in the recent versions or not, but something to ponder.....

This is why I posted this because it seemed as though is the scenario I am seeing.

[dsltnr]

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?

[FUBAR]

Really good reading here. I've tried to get my trans builder on board with experimenting and he started to, but he's just so busy and it's hard when he's miles away. We started to mess with the TTVA angles since it seemed the most basic, but I'm beginning to figure out that without looking at the whole picture, it's easy to tell why the idea got put on the back burner.

I never did pursue it because when my builder said, "you can screw stuff up quick with the gov pressure tables" was enough to make me pause. But like with all tuning for the first time, I guess it's just gonna take small, educated changes to get comfortable. I do have a manual the Rich referenced, just wish they had a exclusive 48RE manual. I'm sure once I get a better grasp on the workings of the trans, it should serve has a roadmap to tuning it.

Only reason I want to mess with it, is to gain better tow / haul capability or performance I should say, out of it. Kinda retarded how the thing is set up if you ask me...

[icemanjc1]

Kinda retarded how the thing is set up if you ask me...

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

[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:anitoof: 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.

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