Just come back to the UK from a holiday in the '80 LeSabre Buick 350 motor to France/lux/germ/belge but half way into the trip the lockup for the torque converter stopped working. It always worked religiously cutting in @ 40mph, but I noticed things going wrong when it would cut in instead at 45, 50 say instead and take quite a while to actually settle in enough to want to actuate. Then the next day and until now didn't work at all. I've never touched the transmission before so not quite sure on how the lockup actuates. Presumably a solenoid or something? Checked the wiring and that all showed continuity, but the single wire that plugs into the gearbox- Does the gearbox have to be removed/dismantled in order to get to where the issue could be? Is it likely to be the lockup mechanism itself or some sensor etc? Anyone have experience with this gearbox and this fault? 37k miles on the transmission. Thanks
If the 200 is like the 2004R ( 4speed) The TCC ( torque converter clutch) solenoid is attached to the valve body. Drop the pan, unbolt it, bolt new one in. Common issue on the 2004R, EXCEPT, on the 2004R it keeps the converter locked, when you come to a stop, it nearly stalls the engine, happens more frequently when the trans is hot.
What Mark said is spot on. Also, check the switch on your brake pedal. If it comes out of adjustment, it will not let the converter lockup engage. On a regal, that switch is plastic, and they are known to strip threads.
Thanks guys. Is there any way the solenoid can be tested when it is out of the transmission? presumably you put a rough 12v to it and it should activate/relax? I know the brake lights work, as I checked them after someone almost rear ended me. It was also an idea that the switch/fuse might be blown and that could also have an effect on the solenoid. But the brake lights work, and cruise turns off when brake light applied too.
I’m not sure. I can tell you in a 200-4r, it’s a common failure. I was told they just get clogged up with debris from normal wear. The tci solenoid I use to replace them fits a bunch of different transmissions and splices into the harness. I totally forgot about the fuse, but that’s a great point.
I will second this, I dealt with that exact problem last summer when I had the same issue. The switch had loosened up so much that the switch plunger was all the way out when nothing was pushing on the brake pedal. It was an easy fix once I found it. For 200-4R swaps, there are a lot of creative ways people can and have wired up a TCC, but usually there is at least one switch in series between the brake switch and solenoid on the trans (e.g. vacuum switch or manually controlled toggle switch). The common way I've seen is that with the ignition on, nothing pushing on the brake pedal, the brake switch plunger should be pushed in and the brake switch will be sending 12V to whatever switch is next in series. Pushing the brake pedal lets the brake switch plunger out and opens the circuit, cutting off the 12V to the TCC.
There are two sets of contacts in the brake light switch. Normally open for brake lights, normally closed for TCC. The cruise control should use a separate switch.
Take the solenoid out and look it over for metallic debris keeping it from activating fully. Take the metal cover off and investigate. When it activates it becomes a magnet and eventually attracts enough metal to keep ot from activating all the way. With the pan down you can put 12V to it and when activated while on the transmission you should hear a distinctive "click" and not a weak click.
Just out of interest, because I haven't been able to get to the car since posting, but if presumably I have the four contact brake light switch, then on condition of brake lights carrying 12v when applied, and if TCC requires no continuity then why the need for the four contacts? Esspecially if that internally the shaft has two seperate contacts anyway? How does the TCC through single wire get the signal that 40mph is reached and thus actuate? Through the speed module that splits the cables between the cruise and the speedo or elsewhere? Obviously I want to check the switch and the easy thing first before getting invested with the gearbox itself.
MPH pressure switch is in the pan in series with solenoid. Brake lights turn on when applied, N.O. part of switch. TC is turned off when brakes applied, N.C. part of switch. The switch on the brake pedal isn't going to decide to turn the TC on at a different MPH since it is on all the time the brakes aren't applied.
Okay. Pan is off. The only item that I can access is this item here. It's the only thing I can reasonably access- the single wire coming from both it and the plug for the outside of the case go way into the the top of the case. If this is not the item I need to look at then presumably I need to remove the valve body but I still don't see how I could access whatever (the solenoid?) the wires are connected to at the top of the case. I did remove what looks like a pressure switch, and I have continuity between the two pins- and tried putting about 50psi air pressure through the opening of the item but continuity didn't change- but then I realise now that the body itself could be what needs to be tested. The wire leading to it is cracked but that was my doing when I removed the switch- it's naturally very brittle. But, any advice on accessing what I presume is the solenoid further up the casing? I can't even see where the wires go.
As expected- On this th200c is the solenoid looks to be in an unaccessible place without removal of the valve body. Anyone replaced the solenoid on this specific transmission. Or can link a manual perhaps?
Are you 100% positive you have a Turbo 200? You say you have a Buick 350, it SHOULD have a Turbo 350, even a lot of the V6’s came with Turbo 350’s with one less clutch per clutch pack. Take a pic of the bottom of your trans pan since you have it off.
Okay, looking at this- solenoid is behind the torque converter. https://procarmanuals.com/pdf-online-gm-thm-200c-atsg-automatic-transmission-service-group/ Looks like I have to drop the whole transmission and remove converter to get to the rear of the oil pump. Which is what I feared when I saw those wires snake up the transmission towards the front. https://gbodyforum.com/attachments/tcc-pic2-jpg.148318/ Yes, this vehicle was built in '79 for 1980 year. Came straight to Britain by first owner- it's completely original. Not saying it's a great transmission- or that the th350 wouldn't be better. But this is a th200c and as far as i'm aware it came from the factory as such. I know it's a th200c. I don't think the build sheet puts transmission models on it though? I do have a lot of original paperwork including that.
If you’re going to have to remove the transmission, I’d upgrade to a Turbo 350, the Turbo 200’s are weak. After you replace the solenoid something else may start failing.
I would love to but easier said than done I'm afriad esspecially if you live outside the customer focused locale. If I could find a th350, or any compatible transmission, the price would be astounding unfortunately.. But I can deal with a small fees every now and then- and I can make the time one way or the other. Working with friends for example often makes such things easier and indeed 'fun'.
This video shows the inside of the trans and points out where the pressure switch and solenoid are: Did you check the brake switch? Make sure you are in fact sending 12V to the transmission case when the TCC is intended to be locked up. There are usually at least a couple things in series with the TCC that control it's operation. Check that you can get 12V through all of them. Jumper wires with a temporary toggle switch and a test light connected to a known good ground will help here.
