- Joined
- Nov 4, 2023
- Messages
- 10
New member here. I found this website and forum in a search of issues with a 4T65E transmissions. Whatever help, guidance and referrals you can give me are truly appreciated.
A lot here but will try to be brief as possible.
I have a 2006 Buick Lacrosse V6 3.8L w/4T65E tranny, now at ~77k miles, bought Feb 2022 with ~61k miles. A diag before purchase threw a #1 solenoid but I bought the car anyway. Shortly thereafter, after driving for ~30 minutes, I experienced progressively longer (and clunky) delays downshifting from 2nd to 1st until the car only started from a stop in 2nd. Manually shifting to 1st had no impact as the car would still start up in 2nd. Had a similar issue on highways, stuck in 3rd and not advancing to D (overdrive).
Successive visits to a local reputable transmission repair shop included the following:
So now, the problem that only occurred after the car had been driven for a period now shows up shortly after I pull out of the driveway and is intermittent.
I'm taking back to the transmission shop on Monday and genuinely don’t know what my next steps should be. Any advise, assistance or referrals you can provide would be again greatly appreciated.
Thanks so much and I hope to hear from you.
Matt
A lot here but will try to be brief as possible.
I have a 2006 Buick Lacrosse V6 3.8L w/4T65E tranny, now at ~77k miles, bought Feb 2022 with ~61k miles. A diag before purchase threw a #1 solenoid but I bought the car anyway. Shortly thereafter, after driving for ~30 minutes, I experienced progressively longer (and clunky) delays downshifting from 2nd to 1st until the car only started from a stop in 2nd. Manually shifting to 1st had no impact as the car would still start up in 2nd. Had a similar issue on highways, stuck in 3rd and not advancing to D (overdrive).
Successive visits to a local reputable transmission repair shop included the following:
- 1st visit (Sep 2022) – pulled the tranny, replaced solenoids, shift sensors, tranny filter, certain OEM tranny parts with upgraded parts, installed a TransGo shift kit and replaced with Dexron VI. Allowed for a reasonable relearning period after the repair but the problem continued.
- 2nd visit (Nov 2022) – pulled the tranny again, replaced the solenoids and sensors (2nd time) and replaced a transmission manifold sensor. The problem continued.
- 3rd visit (Apr 2023) – deducing problem to be electrical instead of mechanical, replaced the PCM (programmed by dealer). New PCM installed, their scanner threw codes pointing to the throttle body - never had this code previously. My 3.8 requires an electronic fuel injected throttle body with built-in TPS. Hard to find but located one in China.
- Once installed for the next 500 miles, short and long trips, no issues, car drove beautifully. Then, the problem returned.
- 4th visit (Sep 2023) – had transmission shop compare notes with a trusted mechanic. Mechanic suggested the possibility of a bad torque converter but the transmission shop ruled out. We hadn’t replaced the gas pedal yet (which has an accelerator sensor). Did that, it didn’t fix and we returned the pedal. Transmission shop had NEVER seen this before. They next replaced the valve body with a Sonnax (includes solenoids in the kit). Test drove after the installation, problem is still there.
- 5th visit (last week) – transmission shop in reviewing their materials noted the PCM uses air flow readings to determine transmission shift points. If the mass air flow sensor doesn’t work properly, it could alter the transmission shift pattern. We replaced the mass air flow sensor, drove for over an hour with the scan tool attached and the problem seemed to go away.
So now, the problem that only occurred after the car had been driven for a period now shows up shortly after I pull out of the driveway and is intermittent.
I'm taking back to the transmission shop on Monday and genuinely don’t know what my next steps should be. Any advise, assistance or referrals you can provide would be again greatly appreciated.
Thanks so much and I hope to hear from you.
Matt