Th200c sticking converter

[a.graham52]

I feel like I read the answer somewhere before but cannot find it with searches.

85 cutlass 3.8/200c. If I drive 30 miles back roads I have no issues. If I drive on the interstate for say 10 miles are so, once I leave the torque converter will stay locked in until a 3/2 downshift is forced (ie near stop or manual shift). Also noticed when it happens applying the brakes will not unlock converter.

All seemed to start after it sat all last summer as a backup car. Prior it was doing 800 miles every week including a 500 mile interstate trip. No issues then.

Where should I start looking?

 

[79 USA 1]

I'm not sure if the 3 speed turbo 200 has the same set up as the 200R4 but when I had the 'stuck converter' issue on my 88 SS Monte Carlo it turned out to be a bad solenoid in the transmission. Would act like a manual with the clutch not released,it would stall the engine when coming to a stop. Up shifts were harsh and the performance(?) feel was lacking from the converter locking during the 1-2 shift.
Looking on Rock Auto they list them.

 

[a.graham52]

I'm not sure if the 3 speed turbo 200 has the same set up as the 200R4 but when I had the 'stuck converter' issue on my 88 SS Monte Carlo it turned out to be a bad solenoid in the transmission. Would act like a manual with the clutch not released,it would stall the engine when coming to a stop. Up shifts were harsh and the performance(?) feel was lacking from the converter locking during the 1-2 shift.
Looking on Rock Auto they list them.

i suspect its not the solenoid for the simple fact that once you force a down shift it unlocks. so the solenoid and i assume the way third gear is sensed works as intended. for instance, coming home i creeped down our road at 30mph with the torque conveter locked up. practically idling along. once we went slow enough for the trans to down shift on its own the converter is no longer locked.

 

[ck80]

i suspect its not the solenoid for the simple fact that once you force a down shift it unlocks. so the solenoid and i assume the way third gear is sensed works as intended. for instance, coming home i creeped down our road at 30mph with the torque conveter locked up. practically idling along. once we went slow enough for the trans to down shift on its own the converter is no longer locked.

If you want to go the lazy route, I might have an option for you.

Now, they're franchise based, so your experience may vary. But where I lived we had an aamco transmission center that'd been around FOREVER. Well, to try and keep drumming up business they offered free transmission check-ups with no repair obligation. Let em check it out, tell you what they thought, and just leave with a handshake saying it was a project you save up for.

 

[GM_Guy-Magnet]

FWIW:

I have an 86 version of your same car - 3.8/ 200C and it also sat all winter and just put it on the road last month, It does pretty much the exact same - drive it in town its fine, once on the highway, the TC kicks in fine and drives awesome. But then coming off the Highway, it sticks on. Come to a stop it kicks off. Starting off though, all my gears shift too soon. I'll be in 3rd by 25Miles an hour hear the TC lock at less than 30 Miles an hour. . Its like 3rd gear is barely there.

The TCC solenoid is electrical and runs with a specific resistance. When you add heat to electronics, you end up with more resistance and eventually a circuit failure. Therefore, the logic that mine is bad seems sound since it happens only when hot,

I am doing the TCC solenoid on my 86 this weekend. Picked it up on RockAuto for a few dollars. Got a new Filter and gasket as well as you do need to drop the pan for this and my fluid isn't pretty in pink as it once was. I'll let you know what I find out from the swap and post back.

Will also add here - RockAuto had a "Shift Solenoid" and a "TCC Solenoid" listed for my car though but they don't differentiate more than engine size (they list pans for both the 200r4 and 200C). I bought both parts thinking "since I am there and its only 10 more bucks...", but the 2 just arrived and look exact same - perhaps they are the same part under a different name? I have no idea how many solendoids the TH200C has (yet ) so I'll also post when I have a look with the Pan off. Will post pictures when I'm complete too. Not much detail on this trans anywhere, (books, and directions - nada) so hopefully I can shed light. Stay tuned.

 

[Wageslave]

Where is that solenoid at on a 200C? Mine shorted, and when I took the pan off to replace it, the wire went up above the valve body to somewhere that I couldn't reach without taking the valve body off.

 

[GM_Guy-Magnet]

Where? Not 100% sure but I found this attachment. I may have to drop the Valve body I guess. Certainly a "hold my beer" moment I guess. And more real pics I guess coming to this post this weekend? Most internet searches said it comes out with a couple of bolts and you need to splice the wires. I'll photograph my progress and let us all know.

 

[GM_Guy-Magnet]

UPDATE: I found an online resource with a full tear down of the 200C. You can download it as a PDF. This is loaded with info so I'm still digesting it all. However the link here says solenoid might bolt into the Oil pump. (meaning it may be up in behind the Converter) so this might be a drop the trans repair? Or maybe its not the TCC one. Not sure what I am looking at. Anyway, have a read of pages 17 or so - talks about the solenoid as being possible suspect, but TCC Sol is missing all over but the Oil Sol is listed on Page 55. Shows the part on the Oil pump but I am unclear it bolts on the back or the front of the pump assembly. Anyway - I think I might try some other efforts before dropping trans to do this. (clean grounds, look for bad wiring, etc). Just to be safe, Ordered a new Valve body gasket as I forgot about that and it was cheap - just in case I do end up going that route through the pan.

So regardless, I am waiting another week before jumping into this to read up and to get parts. (note the link needs your ad blocker turned off then you can download it)

https://procarmanuals.com/pdf-online-gm-thm-200c-atsg-automatic-transmission-service-group/

 

[Wageslave]

Behind the converter makes a good bit of sense, considering where the wire I seen was routed. Still may not be a bad repair if not much more than the front pump needs to come off.

 

[GM_Guy-Magnet]

Here's the page from the manual. I think you are right. Part I bought look like it and everything. Do you figure I am looking at the rear of the pump or the front where the TCC attaches?