No lockup in a Metric 200?

[229MonteHO]

I've noticed recently that my torque converter doesn't seem to lockup once I reach cruising speed. I'm going to try doing a fluid change hopefully this weekend. Anybody have any idea where to start with this? Do the torque converter solenoids go bad after a certain period of time?

I drive 45-50 mph to and from work, and I'm thinking this is why my mileage runs between 11 and 13 mpg. And no, my foot isn't heavy. :lol:

Cheers,
Aaron

 

[shotgun]

I played a little with these.

First do a fluid/filter change with Type F (FH) fluid and one bottle of Lucas Trans addiative.

After that you will need to get a wiring diagram from a shop manual.
There is a easy way to check the solenoid with 12v,I just don't remember what pin it is (thus the manual).

If it checks ok,start looking upstream in the electric system.

 

[229MonteHO]

Type F? I thought that was for certain Ford trannys. Does it perform some kind of magic trick in a GM trans? I've always gone with Dextron for my GM cars.

Aaron

 

[mhamilton]

I only have a later wiring diagram, but hopefully this will be some help.

Pin A is 12v+ from the brake switch. With the ignition on, and the brake pedal released, you should see 12v there. Pin D is ground, supplied by the ECM when lockup is called for.

Pin B is from the top gear pressure switch, it should provide a ground signal to the ECM when the trans is in 3rd. This may differ slightly between the 200c and 2004r/700r4. The old 200c had the pressure switch in series with the solenoid 12v supply, but the principle of operation is the same.

The solenoid isn't easily replaceable in the 200c--it's in the pump, so the trans has to come apart to get at. Hopefully that is not the problem. The schematic I have shows the TCC solenoid in parallel with a diode, so testing continuity may not give you an accurate indication of its condition.

A shop manual would be invaluable, because of the dependence on all the different sensors before the computer will allow lockup. Is it giving you any codes?

EDIT: I think the best way to test the solenoid is to put 12v to terminal A, and measure the voltage at terminal D . You should see nearly 12v at D with a good coil.

 

[shotgun]

Nic job, mhamilton.

"Does it perform some kind of magic trick in a GM trans?"

Yes, it has more "fricton modifiers" in it then the GM stuff. Gives a firmer,more positive shift with less slippage.

It is an old school trick.

You may have trouble finding it,FH will work also.

I have done this for 25+ years on every GM trans it have touched.

 

[229MonteHO]

Michael, thanks for that bit of info. I know what the plug looks like, but was never sure where to check it for voltage.

Shotgun, I figured it had to be something like that.

Cheers,
Aaron

 

[srercrcr]

Excuse me if I are way off track. A TH200 metric started in 78 doesn't have a lockup converter....that didn't come on the scene til the 80s, but I know not what year. I would get a positive ID on the transmission before I proceeded. Perhaps the shift quadrant (P,R,N, etc) would give you a hint.

 

[229MonteHO]

Sometime today, I'll be crawling under her to check out some other stuff. I'll see what I can find out on the trans while I'm under it. This is my first car with a Metric 200, all others were either a TH350 or 250.

Would the 4 pin connector be located on the driver's side of the case like the 350/250 has? This car was built in March of '81, and any '81 car I've come across it seems the rule books go out the window. Some lockup, some don't. Some have computer HEI's, some have vacuum advance. I was told recently as well that there was a vacuum controlled lockup on some of the earlier ones, so that was another "Hmmm...." moment.

These first lockup applications seem to be trouble prone, according to several people I've talked too. Since the car isn't driven super long distances, and it's by no means a powerhouse, will this have any ill-effects aside from losing a bit of mpg's at high speeds?

Cheers,
Aaron

 

[mhamilton]

The TH200 started out with an open converter in the mid '70s. Lockup model 200c debuted in 1980, with a (ported) vacuum controlled lockup switch. 1981 saw all US cars get the GM CCC computer, and this included the computer controlled lockup.

Canadian cars had different requirements, so those did not get the comptuers, cat converters, or other emission control devices until much later. Those would have still had the vacuum lockup and non-computer carb, HEI, etc.

Aaron, the lockup connector will be on the driver's side.

The big problem driving without lockup will be trans cooling. The cooler circuit interacts with the TCC circuit, so prolonged use (especially highway) will shorten the life of the trans.

 

[Uncletruck]

In all the cases I have come across with the lockup, as stated it is dependent on the other sensors in the CCC system working properly. I noticed that if you fuss around with the mixture control solenoid or throttle position sensors by disconnecting them, you tend to lose the TC lockup. As the CCC sensors and controls on these cars are getting to be well over 20 years old, getting the whole CCC system in these cars to function as it should can be a futile effort. Unfortunately the TC lockup solenoid is controlled by the CCC module.

-UT-