Why does MPH effect shift RPM if it is supposed to hit one and then the other?

I have had this issue on two cars now..... From how it was explained to me by a tuner, the computer will look at both the MPH and RPM tables for a shift. It needs to meet both to make the shift. So, my question is this.... IF the MPH was ~10 mph below what it would actually be at the given shift RPM, why would the car shift before the 6300 commanded RPM???

Basically the car is shifting off of the MPH and not the RPM.

Does it actually look at one then the other or do they need to be with in a certain window????

I had this issue on a stock trans 06 gto and it appears to have gone away now that I bumped the mph up closer to actual. It is doing it on my 00 z28 with FLT Level 4 tranny now. I just completed this car and am working out the shift points and stuff now.

Just trying to understand how/why it is doing what it is. The tuner said that it may be something in the computer protecting the trans, but all the tq mgmt should be disabled from what I can see.

I want it to shift off of ONLY the commanded RPM, so I just need to figure out what needs to be done to accomplish this.

Thank you!!!!

It is *possible* that your O/S shifts off of MPH only. I always make sure the MPH is close to the desired shift RPM.

You should log with scanner to adjust shift points. If you have a big gap between MPH and RPM shiftpoints it may not shift as desired.

Transmission tuning depends a lot on personal preference, so you must log data to tune it right for you.

You can make a spreadsheet in excel to extrapolate the stock values and adjust them in your tune. Make a few runs and log data and fine tune the shift points until it shifts exactly as you wish.

Remember, the transmission is still a mechanical component, so it isn't very precise. It needs time to shift, components need time to move.

my OS was a fresh stock A4 tune loaded in by a Tech II due to m6-a4 conversion. I then modified it with my HP tuners so it would run and then went to a tuner to get it right. He didn't replace the entire file so I could still use my HP tuners and not need another license.

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Originally Posted by Montecarlodrag

You should log with scanner to adjust shift points. If you have a big gap between MPH and RPM shiftpoints it may not shift as desired.

Transmission tuning depends a lot on personal preference, so you must log data to tune it right for you.

You can make a spreadsheet in excel to extrapolate the stock values and adjust them in your tune. Make a few runs and log data and fine tune the shift points until it shifts exactly as you wish.

Remember, the transmission is still a mechanical component, so it isn't very precise. It needs time to shift, components need time to move.

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That is what I have been doing. I manually shifted it to the revlimiter while data logging and then looked at the file to see what MPH I was really at the various RPMs. I have since adjusted them but have not been out on the road to re-check due to rain....:mad:

I just want to know IF it is truely that the pcm looks to meet one and then the other or IF they have to be close? I am assuming that the MPH should always be the one to be met first?

It dosen't always wait for both speed and rpm to be met. There is a setting for each gear that tells it rpm, speed, or both. You can't change it in HPT so your stuck with how your calibration has them set from the factory. For most Gen III stuff like yours, the factory settings are usually first gear is MPH only, the rest are MPH and Speed.

had it out for an hour and a half data logging and adjusting. Now it looks like it is shifting alright. Only problem now is the KR that it seems to get when I first hit the gas. I have to try to figure out if something is hitting or something... It goes away at about the 1/8 mile. I guess it takes that long to go back to zero......

I set the shift up WOT MPH to 0 for the 1/2, 2/3, and 3/4 shifts on all vehicles I tune that want a strict WOT RPM shift
then its 100% shift by RPM

^^^ so you mean zero out WOT for 1/2 2/3 and 3/4 an its going to shift by the given RPM?

how can there be such conflicting info on this....????:banghead:

I guess I will try it and see what happens. Only takes a couple of key strokes and a blast down the road. would be great if it works. Maybe if the values are off by so much, it will default to RPM for sure???

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Originally Posted by =fast=

^^^ so you mean zero out WOT for 1/2 2/3 and 3/4 an its going to shift by the given RPM?

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yes...

the only issue you might find is that our 4l60/4l80's all shift slow... so you may have to set it a couple hundred RPM lower than your desired RPM.

make sure you zero out the adaptive shift tables too and you will have a consistent shift every time..

some cars I've had to set the 1st gear rpm to 5800 to get it to shift around 6200 because of the fast speed of the gear and the torque converter on the vehicle...
but as long as I zero out the adaptive shift tables...its shift at the same rpm every time

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Originally Posted by soundengineer

yes...

the only issue you might find is that our 4l60/4l80's all shift slow... so you may have to set it a couple hundred RPM lower than your desired RPM.

make sure you zero out the adaptive shift tables too and you will have a consistent shift every time..

some cars I've had to set the 1st gear rpm to 5800 to get it to shift around 6200 because of the fast speed of the gear and the torque converter on the vehicle...
but as long as I zero out the adaptive shift tables...its shift at the same rpm every time

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Yep, I noticed that on the 1-2.... I will go and zero out the adaptive tables and try this. thank you

i zero out the wot mph, i need to zero out the adaptive tables where are those at?

Trans -> Shift Properties -> Desired Shift Time
both normal and performance tables

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Originally Posted by soundengineer

Trans -> Shift Properties -> Desired Shift Time
both normal and performance tables

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Isn't this the table that says I will take ~.3 seconds, at this torque, to change gears?

So I don't understand why you would need to zero this table too? Zeroing it would just firm up the shift (from a quicker shift) right?

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Originally Posted by waynehartwig

Isn't this the table that says I will take ~.3 seconds, at this torque, to change gears?

So I don't understand why you would need to zero this table too? Zeroing it would just firm up the shift (from a quicker shift) right?

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Has nothing to do with how firm the shift it

and if the calculated engine torque was actually accurate then that table would be useful..
But as soon as you mod the vehicle(even just a maf descreen) it all goes out the window
putting it all at zero atleat makes your shifts consistent

technically you could put it at any flat value and that is doing the same thing.. But why add time when you can command it to shift when you want it to

and if you have an aftermarket stall or have changed anything at all in the transmission parameters... Then it's going to shift differently than stock anyways

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Originally Posted by soundengineer

make sure you zero out the adaptive shift tables too and you will have a consistent shift every time..

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I've heard people say that f bodies use adaptive shift. (TAP)

No one seems to have solid proof that it exists.

Under VCM controls >>>Trans >>> there are two inactive reset buttons, one under Trans Adapts, one under Trans Fast Adapt. If it existed in an f body these would be active buttons.

Theres a table in editor, transmission section, under the Trans tab >>> General Presures. General Adapt is disabled from the factory.
Adapt Counters, and Pressure Control have constants that obviously don't change. Got to thank HP Tuners for the info on that one, hit F1 and a blank page pops up.

I've disconnected the battery for 24 hours, and I've done a rewrite entire to reset everything.
I've logged with a pressure gauge connected.

Nothing ever relearns, actual shift times never change, shift pressures never change. (yes they vary according to driving conditions, but they vary consistantly).
It does not matter what you have your trans desired shift times set to, the actual shift time comes from a calculated RPM drop down speed. And who knows why we weren't granted access to that offset table. (maybe it doesn't exist)

So think about that, you can set them to zero, or to 6.82 minutes, your trans is going to shift within that time. And if there is a table to offset the desired shift time, again where is it? It's in the seat of your pants. (in other words you will feel it long before your vcm throws a dtc).

DTC 1811 is not enabled anyway so it would never throw a DTC.

And to debunk a few myths...you CANNOT cause, fix, or create a tie up, bind, flare, or stuck in two gears at once condition through tuning.

Can you prove me wrong?

PS, one more interesting note. The same year f body programming for a Manual transmission has the Trans General Adapts set to Enable. A4 does not. Figure that one out.

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Originally Posted by soundengineer

Has nothing to do with how firm the shift it

and if the calculated engine torque was actually accurate then that table would be useful..
But as soon as you mod the vehicle(even just a maf descreen) it all goes out the window
putting it all at zero atleat makes your shifts consistent

technically you could put it at any flat value and that is doing the same thing.. But why add time when you can command it to shift when you want it to

and if you have an aftermarket stall or have changed anything at all in the transmission parameters... Then it's going to shift differently than stock anyways

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I didn't mean firm and now that I think about it, I guess I meant quicker. So by quicker shifts, it's giving a 'firmer' feel.

Doesn't the PCM use RPM and timing to figure out torque? IE at x timing/RPM you have x torque.

Still interesting.... Don't know everything on tuning, so I still like hearing others take on it.

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Originally Posted by soundengineer

Trans -> Shift Properties -> Desired Shift Time
both normal and performance tables

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Thanks, thats what i was thinking it was...