Hello everyone,


This one is kind of a mystery, and at this point, I’m honestly a little confused and would love to hear some opinions. I tried to explain everything clearly below because I feel like I may be overlooking something. Originally, I replaced the transmission and torque converter because my car had been throwing a P0740 code for a few months. Then one day, while making a left turn, the car suddenly stalled and came to a hard stop in the middle of an intersection. It made a loud clicking/ratcheting sound that almost sounded like Park trying to engage while moving. After that, the car would not move. I talked to a lot of people and read a lot of posts, and almost everyone said that P0740 usually points to a bad torque converter. Since I was already planning to replace the converter, I decided to install a lower-mileage transmission at the same time instead of replacing only the converter. I installed a complete transmission, torque converter, and donor mechatronic from another XJ with around 48k miles. What has me confused is that I’m still getting P0740, and now I’m also getting P2764. I know anything is possible, but it would seem pretty unlucky if both torque converters happened to be bad, so I’m starting to wonder if something else is actually causing this, maybe even electrical, or if the new transmission TCM is a replacement, do I need to configure it in SDD?

Vehicle:

• 2012 Jaguar XJ (X351)
• 5.0 Naturally Aspirated
• ZF 6HP28

Original issue:

The original transmission had a persistent P0740. The car actually drove mostly normally for a while. Then one day, while turning left, there was a loud clicking/ratcheting sound that sounded almost like Park trying to engage while moving. The car stopped abruptly and would no longer move afterward, which is similar to what the car is doing right now.

Replacement setup:

• Installed transmission and torque converter from a 2013 XJ (~48k miles)
• Opened transmission only to replace:
  • Filter
  • bridge seal
  • cylindrical/mechatronic seals
  • connector sleeve seal
• Used correct ZF seals
• Followed the ZF torque sequence carefully
• Did not disassemble valve body
• Did not remove individual solenoids

Current symptoms:

• The car starts and drives, but shows that it has a gearbox fault.
• Transmission engages gears somewhat normally, but p0740 and p2764 don't disappear. P0740 does for a minute if I clear the codes, but comes back pretty quickly.
• No major shudder
• No major slipping
• No major harsh shifts
• Shifts may feel slightly elevated, but nothing dramatic.

Important behavior:

• P0740 seems to remain stored consistently
• P2764 only appears after revving the engine to around ~4000 RPM
• Sometimes reverse works, but sometimes when I put it into reverse while I'm backing up, it will suddenly stop, and I can't hear the parking pawl clicking into position.

Verified:

• Transmission fluid level checked multiple times and appears correct using Pentosin ATF6
• The charging system confirmed good
• Transmission module voltage while running is normal

Current transmission DTCs:

• P2764 – Torque converter clutch pressure control solenoid control – circuit low
• P0740 – Torque converter clutch solenoid – circuit/open

Other modules:

Intermittent U0402 / invalid data received from transmission control module after transmission faults.

My question:

Most Jaguar techs I’ve talked to say P0740 almost always ends up being the torque converter.

But:

• I now also have P2764--Torque converter clutch pressure control solenoid control - circuit low
• P2764 appears conditionally (mostly high RPM)

Does this sound more like:

1. Am I the one in a million that actually has a dead TCC solenoid, which is causing P0740?
2. Donor mechatronic issue?
3. Since it's showing up in both transmissions, is it possibly a software or even an electrical harness issue?

Trying to decide whether to:

• Replace solenoids?
• Replace mechatronic?
• Pull the transmission again for the converter?
• Investigate wiring/configuration first?

Would love to hear from anyone with actual X351 / ZF 6HP28 experience! Besides this major problem, the car is running great and I would genuinely appreciate any advice or someone who has experienced this before. Thanks for everything, and I look forward to hearing any feedback!