2008 Lucerne 3.8 4 speed automatic..TC or tranny?

[Donnamg]

Hello, my first post here and thanks for accepting me into your site!
My 2008 Lucerne has been a nightmare since I bought it from the dealer in 2013. I had tranny rebuilt at 60 k miles in 2017, engine rebuilt at 68k miles and now I am told my torc converter is bad and it along with my tranny needs to be rebuilt again.
It started last week after we had the fuel pump replaced. It started shuddering when driving at speeds between 20-35 mph and seemed to clear up when going above 45mph. I only drove it once to store about 5 miles away and then the other day to have it diagnosed which was about 8 miles away. Today, when I took it for a second opinion, it shuddered almost the entire time, with getting on highway and driving at 60 mph and off at stop and goes.
I guess my question is, does the Transmission need to be rebuilt with a failing torc converter? This car has cost me more than it’s worth and would like to fix and sell it. It only has 111,000. Both shops told me it is the TC that is bad.
Thank you for any insight and advice you can give me. Oh..can I safely drive it about a half hour away on the highway again to get it to the shop without breaking down on highway? I can feel the tranny shifting normally into its gears, have not tried passing gear but normal shifting. No noise, no burnt tranny fluid and haven’t noticed it accelerating on its own, maybe slight loss of power.
Thanks again!!
Donna

[maxwedge]

That shuddering is often misdiagnosed as a transmission problem , when it is an ignition misfire, most prevalent going up a moderate incline. A knowledgeable tech should scan the pcm under the conditions it occurs and look at misfire counts. If this occurred only after a fuel pump change, the fuel pressure should be checked also.

[Donnamg]

Hi Maxwedge,

Thank you for getting back to me. When I took it for a diagnosis, the printed report says.Problem felt on test drive. Felt more like drive line shudder or engine misfire. No codes stored in any modules. No misfire history readings. Test drove vehicle with scanner on board. Monitored torque converter clutch slip. Should not exceed 50 rpm. Routinely saw slip readings around 150-200 rpm when problem is occurring. Problem gets better if torque converter clutch duty cycle is increased to 100%. This indicates a slippage in the TC clutch which is internal to the transmission. Suggest transmission rebuild or replacement.
This is pretty much Greek to me..so that is the info I have, just don’t what to make of it. We did put some Lucas fuel injector cleaner in it, thinking since we drove around with gas fumes for 5 days from bad fuel filter seal maybe we clogged them up. The shudder wasn’t happening going up a slight incline but more after being stopped and accelerating. It seems to be worse than when it first started. So, if this indeed is a failing TCC, does tranny need rebuilt too? Is it safe to drive it in about 20 miles to shop?

[maxwedge]

If in fact the trans is an issue you would get a code set for tcc or internal pressure issues, try driving in mid range selection, drive 3, this prevents the tcc from engaging, see what happens. Is the trans under warranty?

[Donnamg]

Good Morning,

Unfortunately I did not know about eliminating TCC by driving it in 3 before dropping it off to shop early this morning. I previously stated it wasn’t shuddering when going up an incline..well this morning when getting on freeway ramp, that is when shuddering started. No, trans is not under warranty. It was the first time it was rebuilt in 2017, but not now. The only time the check engine light came on was after we had fuel pump replaced and it was leaking..throwing “Tighten fuel cap” on dash and a P0455 code for large evap leak. After we returned home 5 days later and original O ring was put back on, code was reset and check engine light went off. I will update you when I get a call from shop where it’s at and let you know what they say. Thank you!