A few months ago, I put a ProTorque 2400 in. It gives the car wonderful off-the-line performance. I like the change a lot even though it didn't help my quarter-mile times too much. My reaction times went down A LOT, though, since I don't have to power brake so much. But, when I'm cruising on the freeway, I've found that either the lockup won't engage sometimes (around 60 MPH), or after being locked up for awhile it'll disengage, then quickly re-engage (usually around 75 MPH) from time, to time. This quick disengage/re-engage happened 3 times in a 25-mile freeway jaunt the other day. But then it didn't happen at all today. Once, I couldn't get the thing to re-hook up (by accelerating, then coasting back down with light throttle). After I gave up, and about a mile or so later, it hooked back up on its own.

I put in a West Coast Corvettes computer last month to try to fix the problem. It quickened my G-Tech 0-60 times by probably .2 seconds (from typical 5.1's to 4.9's at 4600 ft, around 60 degrees). And it makes the engage/disengage happen more crisply, and seems to have made the car more likely to re-lockup right away if it happened to disengage, but the computer really hasn't made the problem go away.

When this happens, I'm moving at a constant speed, and I'm not changing throttle position. In fact, after the T/C locks back up, I can even give a little gas to make the car accelerate in overdrive, and it'll stay locked up like I would expect.

Am I getting a little clutch slip? Is there something I can look for with the autotap? I heard that this computer won't throw any slip codes since it's been programmed for the higher stall speed. The local tranny shop is going to try to diagnose it next week for me, but I worry that it'll be hard for them to dup or diagnose since they don't see a lot of Vettes with after-market torque converters.

 

:confused: It certainly doesn't sound as if your TC was installed right. You said your tranny shop didn't have a lot of experience with new vettes and TC's. Hopefully a tech will chime in. I'm really :confused: about your 1/4 mile statement, your stall should of picked you up by 3-5/10th's. Goodluck..

 

Yeah, I wondered if there was an install clearance issue with making the clutch not slip? I'm sure I don't know what I'm talking about. My quarter mile times improved by 15/100ths of a second on average. My previous best was 13.81 at 101.9. After the T/C, I got a 13.66 at 100.3 and had to learn about letting off the gas to get traction off the line, but it was fun to be able to spin the wheels! I haven't had a chance to hit the track with the new computer.

 

I have a Yank Torque converter. My questions is how can you tell when the converter lockup is engaged or disengaged?

 

Jim, take your car into the dealer and have them check the lockup with a tech II scan tool. I had to do this with my yank convertor and found the lockup clutch was junk. Hope this helps!

 

I bet the lockup problem is only in 4th gear???
Then you have the same problem, I have!
Mine unlocks at about 75mph an normal cruising without chainging throttle
also.
Seems to have something to do with the torque management.

Michael


BTW, I got about 4tenths with the TC mod.

 

I have had the same problem with my 2600 Vigilante. I thought I might be the only one, but obviously not. I have a feeling that it might be the torque management as well. Since I have my computer being redone at MTI, I will point this out to them and see if they can fix this problem.

john

 

John, let us know if you can fix it!!!!

It´s a problem that I see more often than you think!!!

Michael

 

Austrian Vette:
How could you tell the converter lockup was disengaging?

Dave00C5:
I don't want to take it to a dealer if there isn't a problem. I wanted to know how I tell if I even have a problem. The car seems to run fine on the interstate.

 

If you go about 75mph and do not change throttle position and suddenly the rpms climb (without moving the car forward) and then suddenly go back where they are then the TC engaged and locked up again.
On my car it does so and sometimes locks up again, sometimes it doesn´t lock up gain.
If it deosn´t lock up again, I have to stop, shut off, and after starting the car again, the Tc locks up again.
But sometimes it throws the 1870 code (transmission component slipping)
and then I have to clear the code to get the TC lockup back.
It must have to be the torques management, I think.
The car thinks the transmission is slipping, that`s because of the TC and throws a code.
Remember, that´s only in 4th gear!!
No problem with the lockup in 3rd!!

Hope that helps! (I´m not that good in English:))

Michael


[Modified by Austrian Vette, 8:04 PM 10/20/2001]

 

What you are describing is totally foreign to me. My PT-2400 works fine, no problem, I luv it. See my 60' time. You need to have your converter checked out. :confused:


[Modified by wallstAL, 12:33 PM 10/20/2001]

 

Austrian Vette I agree there are issues with the A4, esp when mods are added to increase engine performance, torque converter changed to a higher stall rate and when PCM tuners **** with A4 parameters.
I have been asking those who send me a PCM trace to analyze to include TCC parameters and see too much TCC / lockup issues.

I think the A4 tuning has not been looked at indepth by the owners and are unaware they have made performance mod changes and the A4 is not in tune to react to those increased performance changes.

I think a clue to T.M or TCC issues is when monitoring PCM to also add the Delivered torque parameter and if seeing a lot of reported torque of over 1,200 ft/lbs is pointing to a TCC / lockup issue.
I'd like to see more traces of A4 owners since I have a MN6 and thus need more A4 traces to zoom in on the issue, if A4 owners will e-mail ther PCM traces to me.

 

What AUTOTAP parameter would you need to look at??

Michael

 

Probably delivered Torque, requested torque, timing, TCC enable/TSS solonoid status, gear, etc.

See my request for additonal information.
http://forums.corvetteforum.com/zerothread?id=170027

:confused:

 

These would be of help : http://teamzr1.com/a4.html

Can be atap or Ease Scanner traces

 

I get the same problem sometimes. It would unlock for no reason. What I do to get rid of it is to turn off the car and restart and the problem goes away.
When I drive in the city I keep it in OD/3rd and it seems that helps.

 

From the posts above, it sounds like the problem may be happening only between about 1800 rpm (approx stall speed of stock converter) and the stall speed of the new converter. That would be the range where the PCM is expecting no slippage (since it thinks the stock converter is still there) but it's noticing that some slippage is occurring. Above the stall speed of the new converter, there is virtually no slippage, and the PCM is happy.
First question: does this theory sound correct?
Second question: does it tell us anything about how to solve, or work around, the problem?
I'd like to put a different converter in my car but have avoided doing so because I've seen too many posts like this one. Some guys are happy but some are not. Also, it seems that the 2001 cars are more prone to codes and problems than previous years.

 

That's a great track time improvement. Before the mod, were you power-braking up before launching? I would have to brake big time in order to avoid bogging down to low RPM right after launch (high altitude). Also, did your trap speed go up or down with the mod? Mine dropped nearly 2 miles per hour, which was kind of a bummer.

 

I wondered about this as well. My friend called a local torque converter place, and that guy said that stall speed should have no effect on lockup engaging or not. Once the clutch engages, there should be no slippage, even with a high stall converter, because the clutch is doing all the work. But I have a feeling that the computer is detecting slippage, even with the clutch on, and that's why it's popping out of lock up. Now that I have the names of more parameters to monitor (namely that TCC Enable variable, which I hadn't noticed under the transmission category), I'll check out this theory and post the results. I'll also watch for that delivered torque number.

 

Y2Kredauto,

I still do powerbrake my Vigilante to 2000rpm and then be careful on the gas.
Not ease on it but don´t stomp it then.
Otherwise I would even spin my MT´s with my high (2,55Str) on our
not sticky race tracks (mostly normal streets that are closed for the race event). The 2,55 turned out to be little to high for my needs (would be great for a dragtrack with VHT), but I love the aggressive launches and when you get used to it you still can get some awesome fast launches.

I just won against a 2000C5 head / cam +150 NOS car on my last event though he was on MT drags and also with front shocks unhooked (as I have also :)). That was two carlenghts on an 1/8 mile race.
The setup I have is damn fast. Video comes soon!! :D

Michael