Automatic down shifting rough C-6

[LC2001]

[Online]


Join Date: Mar 2003
Location: Ohio
Posts: 12
My Corvette(s):
Gold73 M.RED 2001

When I put the pedal to the floor to pass at 40-50 MPH the down shift is rough and it picks a gear that it shifts out of within a second or two then it smooths out and is fine. I think it is not good to rev so high for a second then shift again. Do I have a service problem or is this the way they all act. I have an 09 but has this been a problem with C-6's?

My 01 or 04 did not pick a gear that was almost at red line and shift again right away.
Lyle

 

[8850]

According to the program via HP Tuner the 09 you should be shifting back to 2nd gear in the 40-50 mph range. That should be no more than about 4000 rpm. Not sure what you mean by rough. Sounds like you may have a problem.

 

[LC2001]

What speed would the shift to 3rd happen ? The shifts are like bang bang second to third so maybe it is ok.

 

[8850]

Here's the table for gears 1-4 upshift and downshift.

 

[LC2001]

The chart is great thanks. If I was going 55 it shifts into second and at 68 it shifts out into 3rd. The time it takes between 55 and 68 is so quick I thought I had a problem. I will go make a few runs today and check it out.
Thanks
Lyle

 

[8850]

Yes, that's what you are feeling. Even 66 it will shift back to 2nd and then to 3rd at 68 based on the program. That happens pretty quick. Not sure why GM made the numbers so close but that's what the program indicates. Maybe the roughness is just the normal feeling you are getting with such quick shifting. Looks like everything is ok!

 

[c4c5specialist]

Hold on there.
Vehicle speed is NOT how the shifting occurs.
It is by vehicle output shaft speed, so if you have the performance axle ratio, that changes.
Also, your comparing a transmission like the 01/04 4L60-E to the 6L80. These 2 transmission operate completely differently.
The truth is, HPtuner changes calibrations and read the programming of the TCM completely differently, so that the layman can attempt to modify shift points and line pressures.
Depending on your options, meaning rear axle ratio, your shift points can differ substantially.
They will also differ if you have the transmission in D or S with your shifter.
Allthebest, c4c5

 

[8850]

Hold on there.
Vehicle speed is NOT how the shifting occurs.
It is by vehicle output shaft speed, so if you have the performance axle ratio, that changes.
Also, your comparing a transmission like the 01/04 4L60-E to the 6L80. These 2 transmission operate completely differently.
The truth is, HPtuner changes calibrations and read the programming of the TCM completely differently, so that the layman can attempt to modify shift points and line pressures.
Depending on your options, meaning rear axle ratio, your shift points can differ substantially.
They will also differ if you have the transmission in D or S with your shifter.
Allthebest, c4c5

"Hold on there" That is a table from an 09 A6 tranny. Only 4 gears are showing as the tables are broken down that way in the program to show only the first four then the other two in another table.

 

[LC2001]

I have the standard rear axle ratio and I'm talking about how it operates in D. I'm thinking at say 55 I will put the selector in S then paddle down to 3rd and see how it acts. If I floor it will it still go into second? I will give it a try and find out.
Lyle

 

[c4c5specialist]

Yes, I am aware its an 09, and its still not the accurate way to understand shifting calibrations of a 6L80.
HP has been doing this even for its 4L60 and its still not accurate.
Allthebest, c4c5

 

[KorvetteKen]

[Online]


Join Date: Mar 2003
Location: Ohio
Posts: 12
My Corvette(s):
Gold73 M.RED 2001

When I put the pedal to the floor to pass at 40-50 MPH the down shift is rough and it picks a gear that it shifts out of within a second or two then it smooths out and is fine. I think it is not good to rev so high for a second then shift again. Do I have a service problem or is this the way they all act. I have an 09 but has this been a problem with C-6's?

My 01 or 04 did not pick a gear that was almost at red line and shift again right away.
Lyle

I think you might be speaking of the abrupt down shift when nailing the throttle from a higher gear. This is normal at least in mine.