"87 EC with 305 and metric 200 trans. The torque converter keep locking and unlocking while out on the highway. This is constant on/off situation. Any ideas what can be causing this? The only changes from stock is that the air pump was frozen so I took off the associated smog equipment. Distributor and carb are still computer controlled.

I can't believe GM was using that POS transmission in '87. I had that in my '85 and after the second time it crapped out I had a TH350 put in. Don't spend any money on a metric 200. That is a light duty trans and it has no business behind a V8 even a 305. You can have a rebuilt TH350 trans installed for about the same price as overhauling a metric 200.

A TH350 trans works real good with a 2.41 real axle ratio and will replace a metric 200 without any mods.

Doug

You are so right. I am very aware of the 200's reputation. This particular trans was rebuilt last year by the previous owner but that means nothing. I have a 700R4 ready to go in already. What I need to know is why is the converter locking/unlocking all the time, if it's a problem with the ECM then it's hitting the trash barrel too. If it's just the trans then I will be rid of it soon.

Since the converter locks up part of the time, I doubt the computer is the problem. Even if it is you can wire around it with a kit from Bowtie Overdrives. Link
http://www.bowtieoverdrives.com/catalog/catalog.php?Action=GETSUBCAT&CATID=OA1

Doug

If it's an 87 it's probably has a 200-4r transmission, which is a good transmission. The ECM controls the torque convertor lockup. First, you need a scanner to see what the ECM is doing. It may be something as simple as the TCC unlock switch on the brake pedal or the 4th gear pressure switch.

Hey Ernie, does a 200-4R trans have "metric" embossed on the pan like a 200 metric?

Doug

It is definitely a metric 200, there is no overdrive. Also the gear indicator is only for a 3 speed. I am changing all this so what is in there is a moot point. All I need to know is if the constant lock/unlock problem is trans related or computer related. I will be removing all trans related possibilities but I need to know if the computer could possibly be acting up causing this problem. If it is, then I will have to replace or do away with the computer. I have a scanner, albeit not a real good one, all it showed was a faulty EGR code.

Hey Ernie, does a 200-4R trans have "metric" embossed on the pan like a 200 metric?
Yes Doug. It says "METRIC" in caps on the bottom driver side of the pan. It also says "Hydra-matic".

Could also be the convertor too. But the computer needs to be checked to see if the ecm is telling the lock up solenoid to turn off and on. Or the solenoid its self.

Thanks bigdave, I had a trans expert tell me almost the same thing except he didn't feel the computer was the problem. It doesn't matter the trans and the computer are both coming out of the car soon.

what does it do when the conver stops?

Engine speed drops or climbs 300-400 rpm when it locks or unlocks.

your welcome man i used to work for a tranny shop. so i hope it helped you out.

what does it do when the conver stops?

it would not move if the convertor goes out completly its like the clutch tha connects the engine to the trans. it has controlled slippage inside.

This response is a little late, but better than never. Right? I had the same problem and found the problem was a faulty Throttle position Sensor (TPS). Apparently, the rheostat had a bad spot in the coil. The TPS is located in the electronic carburretor. About $26.00 from Auto Zone, if memory serves me correctly. Before you replace it, be sure you know how to adjst the voltage and make sure you have the adjsuting tool in hand, otherwise, it's a pain in the butt.

true that could also cause the same things as could a faulty brake switch

true that could also cause the same things as could a faulty brake switch

This response is a little late, but better than never. Right? I had the same problem and found the problem was a faulty Throttle position Sensor (TPS). Apparently, the rheostat had a bad spot in the coil. The TPS is located in the electronic carburetor. About $26.00 from Auto Zone, if memory serves me correctly. Before you replace it, be sure you know how to adjst the voltage and make sure you have the adjsuting tool in hand, otherwise, it's a pain in the butt.

Mee too, EXACTLY!

I had an 87 Olds V6., Metric 200C tranny. Rebuilt the carb and didn't adjust the TPS correctly. It would go into overdrive when passing and run around unlocked when at a constant speed. :mad:

Once I adjusted the TPS correctly the problem went away completely.

(Technospeek: My computer wouldn't read TPS voltages below 1.0 volts and because of the poorly adjusted TPS, that wasn't occuring until 1/2 throttle or above in my case)

One other point.
When I explained the behavior to the tranny guy we went for a ride above 40 MPH. Then he mashed on the gas to engage the TCC lockup. He then lightly tapped the brakes and because that unlocked it, he was able to rule out the computer and the tranny/torque converter as the problem.

Try cruising as usual, and then when you see the RPMs drop and you know the TCC's locked up, just tap the brakes and see if it unlocks. If it does it's most likely not the tranny or the computer and is more likely the TPS adjustment (or related computer input signal) as it was in my case.

Good luck.

Isn't 300-400 RPM a lot for a lock up convertor? I know my 700R4 only drops about 50 RPM when it locks up. Maybe the older stuff was a bit different but I didn't think the convertor had that much slippage in it.