RPM Drop - What do you think?

[Jerryl]

Attached is a thread I located doing some researching on rpm drop.
http://www.turbobuick.com/forums/showthread.php?p=1390565#post1390565

DS log indicates shifting from 1-2 at 5025 dropping to 3650
TCC does not indicate a locked condition.
Converter is 10" 2800-3000 stall.
Tranny is 2004R, stock rear.
TA33, 212/212

While not an accurate test of stall verification, the car seems to increase MPH /take off consistently around 2200 rpm. (I can not locate the DS log for verifying stall),

My understanding is that i am looking for around 800 rpm drop.
Any suggestions what to look for?

 

[Lee Thompson]

Tcc

Scan tool will show if ECM commands grounding the solenoid @ the desired speed and conditions. Solenoid could be plugged forcing the convertor to stay in looked mode or the ground wire could be grounded somewhere--ECM would not show locked. TRY unplugging wires from side of trans--also try the brake tap test @ 60 MPH and see if RPM increases--release brake and it should go back to locked if working properly. Sure sounds like the TCC is locked--but I would think your street driving would have very harsh shifts.

 

[JDSfastGN]

i could be wrong but i did not get the impression or the "jumpy" feel that you get when the TC is stuck locked when riding in the car. Its easy enough to unplug it and go for a test ride though. I think its just a very tight converter to the point where its hurting both spool and keeping the car in its powerband

 

[Jerryl]

Scan tool will show if ECM commands grounding the solenoid @ the desired speed and conditions. Solenoid could be plugged forcing the convertor to stay in looked mode or the ground wire could be grounded somewhere--ECM would not show locked. TRY unplugging wires from side of trans--also try the brake tap test @ 60 MPH and see if RPM increases--release brake and it should go back to locked if working properly. Sure sounds like the TCC is locked--but I would think your street driving would have very harsh shifts.

Thanks Lee.
So let me ask 2 dumb rookie type questions.

The fact that the DS log does not show the TCC flag on, does not imply the TCC is not locked (Could have a short in the wire) Is this correct?

If I unplug the wires, this should ensure the TCC does/is not locked?

 

[Lee Thompson]

Almost

I will try to explain how it work--hope this is right.
When in unlock mode the solenoid is open and is dumping pressure oil into the pan. When the ECM is satisfied, it grounds the solenoid (solenoid has power to it all the time the key is on and brake is not applied.) Power wire (+) goes through the brake switch. When ECM grounds the solenoid it shuts off and the oil that was dumping into the pan now applies pressure to the L/U spool which redirects oil inside pump to lock convertor. If, for whatever reason the solenoid won't pass oil through it, then the L/U spool will be forced upward and lock convertor with or without being energized. Maybe some of the pros will chim in.

 

[Jerryl]

Scan tool will show if ECM commands grounding the solenoid @ the desired speed and conditions. Solenoid could be plugged forcing the convertor to stay in looked mode or the ground wire could be grounded somewhere--ECM would not show locked. TRY unplugging wires from side of trans--also try the brake tap test @ 60 MPH and see if RPM increases--release brake and it should go back to locked if working properly. Sure sounds like the TCC is locked--but I would think your street driving would have very harsh shifts.

Finally got some testing done. If I tap the brake, NO rpm change and
TCC indicates "locked condition" on the scantool.
Now, if I lift the brake pedal (with left foot), RPM drops about 200.
So the TCC does not "actiually" lock (??)
If this is the case, theere should not be a LU issue affecting the 1400 rpm drop (??)

 

[Lee Thompson]

adj.

I'm sure you know there is an adj. on the brake pedal. Sound as if when you tap the brake that the adj. is not correct and you are not breaking the + feed to TCC solenoid. When you lift pedal it is out of window so to speak and breaking + feed. If you power brake the car @ what RPM does it start to built boost? Could you have a very tight convertor (1200 RPM or so )? That would explain the large RPM drop on WOT shifts.

 

[Louie L.]

Im a little confused but you are explaining two different issues. The rpm drop at the shift and a non lock up issue at cruise.

The fact that you lifted the brake pedal and it droped 200 rpm leads me to believe that the brake switch is misadjusted. It needs to be pulled away from the pedal enough to allow the 200 rpm drop(ie lock up) to occur unmolested.
The ecm is commanding lock up but the switch is preventing it.

Now the RMP drop at the shift sounds like a tight converter as mentioned before.HTH

 

[Jerryl]

I'm sure you know there is an adj. on the brake pedal. Sound as if when you tap the brake that the adj. is not correct and you are not breaking the + feed to TCC solenoid. When you lift pedal it is out of window so to speak and breaking + feed. If you power brake the car @ what RPM does it start to built boost?

Switch is adjusted , but, it moves out daily (towards the driver) all the D** time and the cruise does not work when it does. This is how I know it is out. So, I push the switch back into the pedal and cruise works. This is what I did before performing the test.

To clarify the test;
I run on the highway 50 mph. Scan tool indicates "TCC on".
Brake tap test, no rpm change.

I lift lightly on the pedal, 200 rpm (lower) change

Will test tomorrow to see what RPM it builds boost (with trans brake)

.... Could you have a very tight converter (1200 RPM or so )? That would explain the large RPM drop on WOT shifts.

"Supposedly" a 10" 2800-3000 LU, New converter.
At take-off (mash throttle from idle) My MPH starts to consistently increase around 2200. I know this is a not true test of stall speed, but, I thought I would be closer to 2800 before the car takes off when I mash the throttle.

 

[Jerryl]

Im a little confused but you are explaining two different issues. The rpm drop at the shift and a non lock up issue at cruise.

The fact that you lifted the brake pedal and it droped 200 rpm leads me to believe that the brake switch is misadjusted. It needs to be pulled away from the pedal enough to allow the 200 rpm drop(ie lock up) to occur unmolested.
The ecm is commanding lock up but the switch is preventing it.

Now the RMP drop at the shift sounds like a tight converter as mentioned before.HTH

Correct. I think Lee thought maybe the TCC was locked all the time, thus contributing to the unacceptable rpm drop.

Basically, I leave the brake pedal in the neutral positon, push the switch forward and leave it. Is this the corect procedure? Anything much further out, the cruise does not activate. (??)

 

[Louie L.]

If i remember correctly the switch needs to be at a happy medium. Once you get down there and mess with it youll be able to figure it out. But i would pull it back just a tad , one click or so to allow lock up.

 

[norbs]

Your switch is worn out put a tyrap on it , and it won't jump out anymore, confusing you. The better the rpm drop the better the converter.

 

[bison]

You wouldnt get the big rpm drop at WOT on the 1-2 if the switch was grounded. It takes a second or more to apply the TCC. You would feel it applying after it shifted to 2nd. Sounds like the converter is really tight.

 

[Jerryl]

Well,
A response from a trans Dufus ............ :tongue:
I was adjusting the wrong switch for LU.
Forgot about the second switch, on top of the brake light/cruise switch.
Ajusted it and the LU works fine.

On a second note:
The rpm is at 2200 for zero vacuum/boost
Stall of 2800m rpm is at 6 psi boost.
Is this about right?

 

[Lee Thompson]

tight

I usually hold the brake until boost starts moving up. Sounds like a very tight convertor for a turbo car. Maybe a convertor for a carb. car.

 

[Jerryl]

I usually hold the brake until boost starts moving up. Sounds like a very tight convertor for a turbo car. Maybe a convertor for a carb. car.

What should I be looking for in "actual converter performance"?
I say "actual", since the 2800 should have been ok.

 

[Lee Thompson]

Rpm

Rented an 04 Grand Prix last weekend--@ WOT it would go to 5800 and drop to 3800.

 

[Jerryl]

Well,
Recorded another "run" on DS with the transbrake on;
MAX rpm was right at 3000, and that was at 15 lbs boost.

So, can one of you give the 101 version of what I need as far as "stall", since I saw the actual 3000 rpm of the 2800-3000 TC rating.

Basically, after some more tuning and, based on the torque this motor puts out, do I need a re-stall even though the converter is in fact stalling at 2800-3000? Or do I lack the understanding on this?

 

[bison]

You should be fine with that unless its builds slow off the t-brake. Be sure you dont have any exhaust leaks. The 212-212 may make it a little lazier below 4000rpm though. If i were running a smaller cam like 205 or less degrees duration at .050 in i would want to take dvantage of the lower rpm at shift points. Ive gone 127+ with mph with the 212-212 in a heavy car. Maybe a little too much for your application.

 

[Lee Thompson]

?

with the brake on and @ 3000 RPM you are @ 15 psi? What RPM are you @ just when the boost gage starts to move off 0? I believe your convertor is way lower than 2800 stall. IMO. Best of luck.