[GTwice]

My brother owns an auto 330d with about 150k miles. Recently the transmission started slipping, but only when cold. By slipping I mean it looks like a torque converter slip, not locking up. When it warms up, it goes back to normal.

What could it be? Worn out TC clutch? Solenoids? Problem with transmission oil? The box had an oil change a couple thousand miles ago, also the engine was remapped recently but not exactly at the same time as this started.

[ovnel]

Originally Posted by GTwice

My brother owns an auto 330d with about 150k miles. Recently the transmission started slipping, but only when cold. By slipping I mean it looks like a torque converter slip, not locking up. When it warms up, it goes back to normal.

What could it be? Worn out TC clutch? Solenoids? Problem with transmission oil? The box had an oil change a couple thousand miles ago, also the engine was remapped recently but not exactly at the same time as this started.

Try resetting adaptations! I had the same issue on both of my 335ds but it fixed itself when I accidentally reset my adaptations.

[Yozh]

I would not reset adaptations but would rather first check you have your fluid level right.

[robnitro]

That's normal. When cold the lockup doesn't happen until it reaches a certain temperature.
Because BMW picked a loose tc for us, it's annoying as fk. Honestly, the stall speed should be a little lower, because the diesel has so much torque and doesn't need revs to move the car.
I think they used a version of the tc from the V8 version of the trans.

[GTwice]

I was able to gather more information, so here it goes:
- I've found references that mention that it's normal with the ZF6HP to run open TC when cold to facilitate warm-up. Thing is, I've seen references in BMW docs that mention that it happens only for 120s after startup, others - until the transmission fluid reaches 35 deg C... it seems that varies, probably with TCU software versions. Definitely it now takes quite a few minutes when cold-starting at temperatures around freezing.
- the slipping definitely started together with remap in the engine, but that also coincided with much colder weather onset
- guy doing the remap mentioned that the car was "already modded" or at least had some DME reflash done to it in the past. He started by updating all of the car modules. It seems possible that after the update TCU received a newer software version with modified warm-up behavior. But it's also possible that he screwed something up and flashed a wrong/older version.

Anyway, the car is going back for a performance transmission flash next week, we'll see afterwards

[robnitro]

Yes, I've seen a time limit and speed limit in the transmission mapping.
The xhp flash license allows you to make your own maps. I have the xdf maps definition file for tunerpro, which I used for editing.

I couldn't get it to respond to the speed one, which I wanted to make it lock up as soon as I go above 50mph on the highway.

There's also a set of tcc lockup maps for cold, which get ignored even if set them identical to the warm tcc maps.

I've never tested the time limit, default is high, like around 10 minutes, last I checked.
I set the temperature lower, to 15C. It's been working fine.

[Asonchadwick]

Probably low on fluid. Or filter clogging up. Fluid shrinks alot when cold and thickens up

[BB_cuda]

Originally Posted by Asonchadwick

Probably low on fluid. Or filter clogging up. Fluid shrinks alot when cold and thickens up

The filter is a joke. It would only catch very coarse particles. I recall a thread where someone cut open the filter and it was very “open”.

[robnitro]

Originally Posted by Asonchadwick

Probably low on fluid. Or filter clogging up. Fluid shrinks alot when cold and thickens up

It's the transmission programming to not lock up the tc when below 30-40C