[Alanrorr1]

The Z4 is in the shop with the transmission apart for codes 5A53 and 5A54 (Gearbox overheating Red and Black phase). They (not dealer) are recommending a new clutch, flywheel and seals. Originally, they thought the temperature sensor in the transmission. What do you think? If their recommendation sounds like the right direction, any ideas to reduce > $5K with aftermarket reliable parts such as where should I go (for the parts since the shop said they could install them)?

Reasons they gave for the diagnosis:
- There was a fair bit of play in the flywheel (maybe 1/64" to 1/32" guess) when moving from side to side. This could be checked since the transmission was dropped
- They said the clutch was pausing at high speed before shifting. I seem to remember that, but I thought it was due to it not being in sport mode and subsequently causing a delay. In sport mode or normal, I felt no slip at 55 mph in 6th with hefty acceleration but maybe I would not notice it?
- Transmission fluid was close to black but had no metal pieces or shavings

When it initially came into the shop, they tried
- filling the transmission fluid with 1.7 quarts (car has 105K miles)
- looked for a wiring issue to the transmission temperature sensor outside of the transmission
- updated the software in the transmission and ECU
Nothing worked, it still overheated.
I liked their ideas so far. I do not think looking for clogged coolant circulation has been checked though

Notes:
- The clutch oil temperature (using Foxwell tool) would match up to the red and black (lower seemed to happen around 315F and the upper around 345F).
- It could shoot up 90 degrees F quickly (have image going from 220F to 310F in 2 seconds)
- This issue started 3 and 1/2 years ago - happened rarely, now frequently
- The first warning could occur within 3 seconds of putting the car into reverse from a cold start (happened multiple times)
- 2 weeks ago, it went into limp mode for 1 hour in park/engine on after driving for 45 minutes. Temperature would not decrease below 330F during the hour

Let me know if you have any ideas or if you think I missed something. Thanks for looking!