C5 Torque problem?
Thread Starter
Heel & Toe
Joined: Jun 2012
Posts: 19
Likes: 0
C5 Torque problem?
Guys have a look at short video:
Set cruise control, going uphill, car tries to keep set speed, increases power, but rpm go wildly up just to cope with slight power requirement for light uphill road. Any guesses what is wrong? Do you think this is torque converter problem? Had transmission fluids changed last month..
Or if I try accelerate above 2 gear and RPMs go above 2k, RPMs increase without adding any real power and if I release gas pedal, then shift changes easily.
C5 1991 Corvette
Set cruise control, going uphill, car tries to keep set speed, increases power, but rpm go wildly up just to cope with slight power requirement for light uphill road. Any guesses what is wrong? Do you think this is torque converter problem? Had transmission fluids changed last month..
Or if I try accelerate above 2 gear and RPMs go above 2k, RPMs increase without adding any real power and if I release gas pedal, then shift changes easily.
C5 1991 Corvette
Le Mans Master
Joined: May 2006
Posts: 7,888
Likes: 260
From: Hillsboro OR
Guys have a look at short video:
http://youtu.be/9fZUh4GxxWA
Set cruise control, going uphill, car tries to keep set speed, increases power, but rpm go wildly up just to cope with slight power requirement for light uphill road. Any guesses what is wrong? Do you think this is torque converter problem? Had transmission fluids changed last month..
Or if I try accelerate above 2 gear and RPMs go above 2k, RPMs increase without adding any real power and if I release gas pedal, then shift changes easily.
C5 1991 Corvette
http://youtu.be/9fZUh4GxxWA
Set cruise control, going uphill, car tries to keep set speed, increases power, but rpm go wildly up just to cope with slight power requirement for light uphill road. Any guesses what is wrong? Do you think this is torque converter problem? Had transmission fluids changed last month..
Or if I try accelerate above 2 gear and RPMs go above 2k, RPMs increase without adding any real power and if I release gas pedal, then shift changes easily.
C5 1991 Corvette
I filled mine when hot. Trans slipped a little in 2nd. I checked it again at the correct temp and, I found I was 22 oz. low.
My other thoughts would be to check the TCC (Torque Converter Clutch enable/disable speeds (MPH) in your tune. IIRC they are ~48/45 MPH respectively.
The TCC will disable when you apply the brake pedal. Make sure the brake pedal/switch is properly adjusted (pull up on the pedal as far as you can). If misadjusted, it will randomly disable the TCC.
HTH.
BTW the "C5" generation years are from 97 - 04.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
ALSO any mis-fire code wether real or false will unlock the TCC---If your car is modded or in a retro fit application---you most always have to desensitize the misfire tables to prevent false misfire codes----
Under normal operation the car should downshift to the gear it needs to keep the speed up---going up a steep hill---sometimes on a gradual hill it will simply unlock the TCC but 1st--but that really only happens if your tuner re-worked the TCC lock/unlock shift tables to let that happen---My guess is a false misfire OR somehow the brake light circuit is activated which will also unlock the TCC as mentioned earlier
Under normal operation the car should downshift to the gear it needs to keep the speed up---going up a steep hill---sometimes on a gradual hill it will simply unlock the TCC but 1st--but that really only happens if your tuner re-worked the TCC lock/unlock shift tables to let that happen---My guess is a false misfire OR somehow the brake light circuit is activated which will also unlock the TCC as mentioned earlier
Thread Starter
Heel & Toe
Joined: Jun 2012
Posts: 19
Likes: 0
Carefully check the fluid level. Trans fluid temp (per Service Manual) MUST be between 87F - 122F to check for proper fluid fill level.
I filled mine when hot. Trans slipped a little in 2nd. I checked it again at the correct temp and, I found I was 22 oz. low.
My other thoughts would be to check the TCC (Torque Converter Clutch enable/disable speeds (MPH) in your tune. IIRC they are ~48/45 MPH respectively.
The TCC will disable when you apply the brake pedal. Make sure the brake pedal/switch is properly adjusted (pull up on the pedal as far as you can). If misadjusted, it will randomly disable the TCC.
HTH.
BTW the "C5" generation years are from 97 - 04.
I filled mine when hot. Trans slipped a little in 2nd. I checked it again at the correct temp and, I found I was 22 oz. low.
My other thoughts would be to check the TCC (Torque Converter Clutch enable/disable speeds (MPH) in your tune. IIRC they are ~48/45 MPH respectively.
The TCC will disable when you apply the brake pedal. Make sure the brake pedal/switch is properly adjusted (pull up on the pedal as far as you can). If misadjusted, it will randomly disable the TCC.
HTH.
BTW the "C5" generation years are from 97 - 04.
Image driving on 2nd gear, keeping RPMs steady at 2000, and at certain point when it is time to change the gear, instead of changing, RPMs go up to ~3000, stay there for couple seconds (if I release gas pedal - gear shifts right away) it slowly changes the gear.
The higher RPMs initially are before changing the gear, more wildly they jump up during gear change moment..
I guess it is hard to imagine all that, but I promise I will get you a descent video clip.
I will get the car to auto transmission specialists in couple days and see what they tell. Just trying to collect some info of what could be wrong before inspection.
Car is standard, no mods.
And sorry, but what was that about TCC speeds? Did not really get it.
Advanced
Joined: Dec 2012
Posts: 72
Likes: 3
From: West Bend Wisconsin
The DIC indicates the cruise had just been disengaged seconds before the video started. The engine revved up when you hit the button to set the cruise again.
I don't know if that is normal for a Corvette (mine is a 6 speed manual), but my 2006 Buick always revs when I set the cruise button. For some reason, it unlocks the torque converter, then locks it again. My previous 2001 GM car did not do that.
Your latest post talks about problems just shifting 2nd to 3rd. A video of just that would be a lot more useful, rather than confusing things with the cruise control.
I don't know if that is normal for a Corvette (mine is a 6 speed manual), but my 2006 Buick always revs when I set the cruise button. For some reason, it unlocks the torque converter, then locks it again. My previous 2001 GM car did not do that.
Your latest post talks about problems just shifting 2nd to 3rd. A video of just that would be a lot more useful, rather than confusing things with the cruise control.
Thread Starter
Heel & Toe
Joined: Jun 2012
Posts: 19
Likes: 0
The DIC indicates the cruise had just been disengaged seconds before the video started. The engine revved up when you hit the button to set the cruise again.
I don't know if that is normal for a Corvette (mine is a 6 speed manual), but my 2006 Buick always revs when I set the cruise button. For some reason, it unlocks the torque converter, then locks it again. My previous 2001 GM car did not do that.
Your latest post talks about problems just shifting 2nd to 3rd. A video of just that would be a lot more useful, rather than confusing things with the cruise control.
I don't know if that is normal for a Corvette (mine is a 6 speed manual), but my 2006 Buick always revs when I set the cruise button. For some reason, it unlocks the torque converter, then locks it again. My previous 2001 GM car did not do that.
Your latest post talks about problems just shifting 2nd to 3rd. A video of just that would be a lot more useful, rather than confusing things with the cruise control.
Video from today.
So I drove the car, shifted to 2nd with no problems, then I pushed gas pedal and kept it at same position, car was increasing speed, and then when it is time to shift a gear, boom RPMs go wildly up and car is reluctant to change the gear. I will repeat myself - gas pedal was kept at the same position all the time.
Le Mans Master
Joined: May 2006
Posts: 7,888
Likes: 260
From: Hillsboro OR
Cruise control was disengaged and engaged again, but if you look at the speed, you will realize that there was no increase in speed, cruise control was set to same speed as car was driving (from previous cruise control set), and there was only light up slope, car tried to add some power, but gearbox? could not manage to add power, so kept increasing rpm to gain in, and there was a need for a lot RPM increase to fight that small uphill.
Video from today.
Video2 - YouTube
So I drove the car, shifted to 2nd with no problems, then I pushed gas pedal and kept it at same position, car was increasing speed, and then when it is time to shift a gear, boom RPMs go wildly up and car is reluctant to change the gear. I will repeat myself - gas pedal was kept at the same position all the time.
Video from today.
Video2 - YouTube
So I drove the car, shifted to 2nd with no problems, then I pushed gas pedal and kept it at same position, car was increasing speed, and then when it is time to shift a gear, boom RPMs go wildly up and car is reluctant to change the gear. I will repeat myself - gas pedal was kept at the same position all the time.
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Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Typically when an auto trans is ready to take a dump--it will begin shifting with a flare in the RPM's as you mention---The strongest clutch pack is the 1-2---Most often you will notice a flare shift in the 3-4 shift as it is the weakest clutch pack--The 2-3 flare shift would be the next most likely to be a sign of trans failure--but more often a 2-3 flare shift id a sign that metal has gotten into your TQ converter and also has begun getting into everywhere---Sorry to say you have all the indications of a failing trans--
PS: a good indicator also is to see what the trans temps are--A failing trans will get very hot very quickly--like over 220* even when running a short time-
PS: a good indicator also is to see what the trans temps are--A failing trans will get very hot very quickly--like over 220* even when running a short time-