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Torque converter lockup problems '91 Caprice


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11-20-02, 07:40 PM   #1  
daveblan
Torque converter lockup problems '91 Caprice

Ive got a '91 Caprice Classice 64k miles 305 A/t power everything. With the help of some previous advice from an earlier post I have ironed out about 95% of my probs with this car. I still have a vibration/hesitation between that is most noticable between @45 and 55 mph, it does do this at slower speeds but as the trans up shifts it goes away. It feels like Im trying to drive a manual trans car in too high a gear for the speed Im going. Im sure it is the torque converter trying to lock up. Sometimes the converter does lock up properly and the car runs great! This is the second trans. in this car, the orig. trany had the same symptoms so some buddys and I replaced it with this one. The unit in the car now is used, but my buddy who gave it to me for 25 bucks assured me that it ran fine before he took it out of his car. He is a good friend and I believe him. My question is could there be an element of the computer that is telling the converter to lock up when it shouldnt and can I or should I disable it. I have found a web site that offers a way to make this trans only lock up in 4th, but its ment for street rodders of retro fits. should I try this , do I need to try this, and would it work. I have no check engine lights coming on and this model and year to my knowledge didnt moniter the trans. anyhow. Any help would be great. My wife is threating to make me sell it!

 
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11-21-02, 03:23 AM   #2  
Joe_F
You might choose to change the solenoid in the valve body area. It's about 40 bucks from a parts store and the most probable cause of the tranny issue.

 
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11-22-02, 04:44 PM   #3  
daveblan
Ill give that a try, thanks. My only reservation is both transmissions having the same problem? Granted the one in the car now is used, but it didnt have this problem in its previous car. By the way thanks for a great site there is an endless amount of information here and some great free advice.

 
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11-22-02, 10:07 PM   #4  
Is that a 700R4 tranny? If so, you should be able to disconnect the TCC electrical connector. Should be close to, and above the speedo cable on the transmission. Disconnect it and see if your shudder stops.

 
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11-23-02, 04:22 AM   #5  
Joe_F
Yes, a 91 Caprice uses a 700R4 tranny.

 
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11-23-02, 06:07 AM   #6  
daveblan
Thanks dirty dan, thats a good idea. I've got to fix the heater this morning also, the cable that controls the hot/cold mix under the dash came off and it naturaly came off while in the cold posistion. We have about 2 inches of snow this morning. The wife is begining to tap her toe even louder about this car.

 
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11-23-02, 10:05 AM   #7  
daveblan
Well the heater is now working again and I disconected the TCC connector as per Dirty Dan's suggestion and lo and behold, the car runs as it should! NO more hesitation!! Now, what do I do. Can I leave this disconected, or does this prove Joe F's diag. that the solenoid is bad and that I should I replace it. This car is used mainly for around town stuff in a very rural area. It sees highway speeds alot, but not long trips. From my test drive after disconecting the connector I couldnt tell if the torque converter was locking up or not. If it isnt I would not have overdrive, correct? Not a big deal for the use the car gets, but I would like to make it right if its not too difficult or expensive. I only bought this car after a major spine surgery so I had somthing BIG and comfortable and easy to get in and out of, that wasnt a truck, (I have 2 of those). Unfortunatly I'm soon headed for another major surgery and am running out of time to play with it.

 
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11-23-02, 12:39 PM   #8  
Probably a bad TCC as Joe said. You may want to get a test light busy and check your wiring.
If you need troubleshooting info, send me a fax number and I will send you a copy from GM. Things that can effect TCC operation are;
Coolant Temp Sensor
TPS
VSS
Faulty (or misadjusted) Brake Light Switch

It will run fine with TCC disconnected with out hurting anything but your gas mileage. If you leave a faulty TCC connected it can hurt your ECM driver if the solenoid coil resistance is less than 20 ohms.
If it's bad, and were mine, I'd replace the TCC, but I wouldn't be in a big rush. It's a simple job (messy) and shouldn't cost any more than $40-50 if you DIY.

 
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11-23-02, 12:51 PM   #9  
Joe_F
I agree with Dan. I have it disconnected on my Cavalier, no issues. I will probably fix it when I service the tranny.

 
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11-24-02, 05:19 PM   #10  
daveblan
I may have seen the light. While doing a little homework before begining my trouble shooting, somthing occured to me. Dirty dan said that the VSS could be one of the things causing my problems. The one part that I removed from my origional transmission and installed on the new/used one was the VSS. The new/used one had a cable drive so I swaped my VSS in its place. This could explain why both transmissions have the same problems. Now, is there a way to troubleshoot a VSS or is it a throw-away-get-a-new-one type thing.

 
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11-24-02, 07:16 PM   #11  
I'll have to look that up. I'll get back to you!

 
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11-24-02, 07:45 PM   #12  
Are you getting a check engine light? Code for VSS would be 24.
Does your cruise control work? Do your backup lights and brake lights work? All of these are involved and I assumed remained on the car.

OK, book says quickest (and Proper) way to check is to go see a mechanic with a scan tool. First to address will be to make sure the ECM knows when it's in Park and Neutral. If that is OK, the VSS pulses fed to scan tool should closely match speedometer reading. Should be able to get diagnostics for <$50.00

At home, and I wouldn't really reccomend this due to safety concerns...

Raise drive wheels, Block, chock and make safe.
Crank engine, Put in drive. let idle in drive, with cruise off.
Backprobe circuit 437 (should be brown wire from VSS) with voltmeter to ground. Voltage should read between 0 and 10 volts and varying. If so, VSS is good.

If voltage is between 5 to 12 volts, not varying...
Recheck connections at VSS
Check for open circuit 437
Check for 12 volt and Ground at VSS
If all are OK, the VSS is bad.

If you get less than 1 volt
write back with FAX number. And I'll send you diagnostic info.

 
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11-25-02, 07:47 AM   #13  
daveblan
Thanks for the help Dirty dan, that sounds like an adventurous way to check the VSS, right up this ole country boys alley! I think it will have to wait till after Thanksgiving. Got a slew of Dr's visits and some traveling to do the next few days (not in this car). When I get back (If I make it, two kids under 4 years, one wife,my mothers' house in the big city, oh boy) Ill give it a try and give you a shout with a fax # if I need that diag info. By the way I have not gotten any codes on the trans. and brake and backup lights work. Again, many thanks, have a safe and blessed Thanksgiving

 
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