98 Century tranny

[public]

Attention all smart people.

Please check out this issue before I waste time and money.
http://www.automotiveforums.com/vbul...d.php?t=332653

Thank you in advance for your help.

[drdisque]

the cooler may be a decent stopgap solution, but there is a bigger problem here. I don't understand what you mean by the "TCC going in and out" though.

[public]

Torque Converter Clutch Solenoid. engaging and releasing

[drdisque]

does this only happen in a certain gear or in all gears?

[public]

Only in 4th at highway speeds. That is when the TCC engages to save fuel. It is a very slight surging.

[curtis73]

I know this gets tossed around A LOT but give it a try anyway. Reset the PCM by pulling the power. Make it a really hard reset by pulling the negative post at the battery and turn on the key for 5 minutes or so. Today's cars have so many capacitance pieces that they can store enough trickle to keep memory. Unless it changed from 96 (where my experience ends) to 98, the TCC lockup is a combination of tranny temp, load, throttle position, and a few other data points from the operation.

I know that GM TCCs will respond to tiny little throttle inputs on the highway and its frustrating. If the PCM has learned something that makes it more sensitive to those changes, it might be doing it on its own.

Nine times out of ten, a tranny fluid change will fix it. Old fluid doesn't have the same friction qualities and sometimes it slips even when the PCM is telling it to engage. A lot of people overlook this assuming that it would act like a slipping clutch and manifest itself as an RPM flare, but TCCs are a whole different animal. They're grabby and don't tend to "slip". If they're "slipping" it sometimes shows up as grip, then no grip. To diagnose that, tap into the TCC wire and put a test light on it.

If the test light goes on and off with the surges, then its a PCM or sensor problem. Check the throttle position sensor, coolant temp sensor, and anything else you can think of. My LT1 wouldn't lock up the TCC because it had a bad coolant temp sensor. They stay unlocked to help warm up the tranny when its cold, and the temp sensor never said it got warm enough.

If the test light stays on during the surges, its a physical problem. Either the fluid has gone too far south and needs to be replaced, or the TC clutch material has become worn and you need a new TC.

Of course, all of the test light business could be replaced with a friend with AutoTap or similar software. You could plug into the OBD2 port and get a readout of when the TCC signal is active.

[public]

Thanks. The fluid and filter are at about 40k miles. I'll go ahead and change that since about half of the fluid doesn't come out with a standard change anyway. I will also reset the PCM. Hopefully avoiding any big purchases.

[curtis73]

You can go to Jiffy Loob or a similar place for a tranny flush. They use a cylinder filled with 15 quarts of fluid and they tap into the cooler lines. Then they start up the engine and the pump pushes the old out and sucks new in from the machine. Pretty slick. I think I had mine done for about $70.

That's probably the last time you'll hear me recommend Jiffy Loob.

[public]

That sounds pretty cool. But, I am always nervous letting a 18 year old under my hood. For $70 I may just live with it until it is time to change the fluid.

I wonder if it could be just a little static in the TPS signal? The TPS stays in that slot ,and has for most of the cars life now. When it is cold the throttle may be in a slightly different position due to air density giving me more power at a lower throttle position.????????????