High rpm part time shifts with 4.10 and tune

[ran260gt]

I just got my 4.10s and a custom 93 SCT X3 tune , and Part time shifts are way to high in the RPM , leaving a light at 1/4 throttle it shifts at 3000 rpms for 1-2 and 2-3 !
WOT is great but this is going to suck for everyday driving , why would the shifts be so high ?

Could it have something to do with my J-MOD ?

thanks for helping out a Mustang Guy?:)

[Vortech347]

Contact whoever did your tune and let them know.

[Local Boy]

The J-Mod affects how it shifts...not when it shifts...

Your tuner needs to lower the shift points...that's all...

ALOHA

[SC Cheesehead]

The J-Mod affects how it shifts...not when it shifts...

Your tuner needs to lower the shift points...that's all...

ALOHA
^^^^^ +1 ^^^^^^

The factory tune has the shift schedule set to shift at low rpms for economy, your performance tune is prolly set with higher shift points to get the engine higher up in the power band before shifting.

You may want to have your tuner provide you with another "economy" tune that you can load on the XCal and install for DD and keep the performance tune loaded on the XCal as well for when you want to have a little fun.

[Darrin]

The J-Mod affects how it shifts...not when it shifts...


Nope, the J-mod does affect when it shifts for sure. Actually a good use for the mod is to lower the shift points to account for a gear change. The mod makes the clutches fill faster. Faster fills mean sooner shifts. You can decrease the fill time on the clutches by a pretty significant amount this way actually.

Normally the complaint from someone with a mod is that it shifts too early.

This one is entirely in the tune.

Darrin

[ran260gt]

Thanks for all the help , going to give the shop a call Monday , Because not only is the problem with the Tuner , there is a steady whine coming from the rear .

This is problably because when I picked up the car , the owner said he FORGOT to tell his guy installing the gears to put in the new bearings :confused:

so I have 630000 mile bearings with new gears , not sure if this is a big deal , but the whinning is a big deal , why cant you take your car to get work done , and have it done right the first time :confused: WTF !

He did say if there is any problem give him a call !

[Local Boy]

Always a pleasure reading your posts, Darin...

Although, I agree with your points...

I stand by my statement...

If your trans is set to shift at a specific point...the trans will not shift until that point comes in range...With of without a J-Mod...

Sure, the mod quickens the time it takes to shift...which leads one to feel like it's shifting earlier...But it still follows the same shift schedule...

At least we agree that this is in the tune...

ALOHA

[Darrin]

Always a pleasure reading your posts, Darin...

Although, I agree with your points...

I stand by my statement...

If your trans is set to shift at a specific point...the trans will not shift until that point comes in range...With of without a J-Mod...

Sure, the mod quickens the time it takes to shift...which leads one to feel like it's shifting earlier...But it still follows the same shift schedule...

At least we agree that this is in the tune...

ALOHA


I appreciate what you are saying, but I don't think you have a handle on the whole picture of how this works.

The pcm hasn't got any adaptive strategy for learning clutch fill times at all. Those are hard set numbers in the programming.

To understand how this all happens you first must understand that the computer only initates a shift by issuing a command to manipulate the shift solenoids and that after this command is issued, a clutch or piston bore still has to either fill or empty for the shift to complete.

I need you to also understand that time is only a number, so please don't get caught up in how big or little a number I use in the following. It is only a number. That is all the computer knows is numbers and it has no ability on it's own to relate those numbers other than how the programming tells it to.

With all this in mind, lets use an hour glass instead of a clutch. With this hour glass we have a constant where once the task is initiated by turning over the hour glass it takes a fixed amount of time, 1 hour in this case, to empty the top reservoir through an orifice and fill the bottom reservoir.

Now let's insert a computer to handle the task of turning over the hour glass for us so that the task completes on time. We know that it takes 1 hour for the hour glass to complete it's cycle and finish the task so we program the computer wth that information. The computer also has it's own clock that is accurate in time and is programmed with a limited anticipation strategy where it watches certain things, like throttle position and rpm, and uses these things to detect when it needs to issue a command to initiate a task so that it is completed on time. Since we have a constant for the time to complete once the task is initiated, we save valuable code by not programming the computer with any logic to measure the actual time for completion. But we do install an error check program where if the task isn't completed within an error threshold time, lets say 1.5 hours after initiation, a failure code will be set.

With those parameters it will turn the glass over 1 hour prior to the anticipated task completion point every time and that works great as long as nobody messes with the hole in the hour glass.

Now, let's modify that hole in the hour glass to empty the top and fill the bottom faster. That makes the task complete sooner. The computer doesn't see that happening because it isn't monitoring how long it takes to complete. It only knows that the task was completed within the error threshold time after the command was issued to initiate the task. Therefore it changes nothing and always continues to initiate the task 1 hour before it needs to complete.

The above scenario is exactly how he computer looks at it, so yes a J-mod definitely does affect shift timing. There is no question about that at all. According to Jerry (the J in the J-mod), by doing this mod you will pretty much cut those clutch fill times in half. Thus, the shift takes about half as long to complete after the command is given to initiate it and the computer doesn't see that part to correct for it. It still always initates the shift going by the programmed clutch fill time.

On a completely stock vehicle this can have a pretty good impact on the rpm that the shift will happen at WOT. Enough so that you can even account for some gear changes through valve body modification alone.

Darrin

[Local Boy]

Thanks for the clarification, Darin...:D

Like I said...

It always a pleasure...:beer:

ALOHA

[ran260gt]

Update , took my car back , got everything fixed up and its running great , I love the 4.10s :burnout:

[Local Boy]

Glad everything worked out...

Now...Drive it, like it's on Fire!

ALOHA