6hp26 issue - 6 speed one

[khizman]

Thought this was the reliable one?

Anyway, torque converter appears to me smashing around.

Doing 50mph on the motorway, throttle down, gear change down is so hard and abrubt it slams.

Leave it in sports mode and the car is great.

Seeing as I have a ramp I am going to change the fluid and filter and see what it's like. If still crap then I plan to rebuild the TC.

[upallnight]

Is the X still under warranty? Perhaps BMW will investigate as to why this trans is failing.

[khizman]

Na way out of warranty.

[bcredliner]

More often than not, bad torque converter symptoms would be grinding or whirring sound in gear at an idle or vibration at some speeds.

Have you checked OBD for any transmission error codes?

[Porando]

I has kind of similar issue with same tranny. Took it to dealer and described problem w/o suggesting anything. They charged me for 1 hour "investigation" ($150)
Told me that they have not found issue ..but problem was indeed gone.
However, during that time they updated software (I checked )
No problem since (3 years?)
When I asked before how much is transmission software update (as I suspected that may help) - was told $360 or so.....

[admranger]

Slam issue is well known and covered in here...

Summary: downshift is abrupt -- feels like you are getting rear ended (complete with whiplash on the worse cases).

try a fluid change -- yeah, I know it's lifetime fluid. Use the ZF LifeGuard 6 fluid. Do the filter too. You need to refill the pan w/the new fluid, then put the plug in hand tight, run the transmission through the gears with the engine on (still on jackstands -- just put your foot on the brake and shift through the gears, pausing for a second at each shift point) and return to park. Leave engine running and remove tranny plug. Add fluid until it runs out. BTW: cat converters are hot. Really hot. Be careful as you put the new fluid in. Transmission needs to be at 85 deg F +/-, so have a temp gauge handy.

This may help a bit or not. I ended up having the transmission replaced under certified pre owned warranty. Ugly proposition due to costs for remanufactured transmission, etc.

It's a nasty problem. Good luck!

[BigBlack48is]

I would strongly suggest a filter change and then top it off with an appropriate fluid. I used redline D4 in mine and it completely fixed my ZF

[khizman]

Changed the fluid reset adaptions etc. Nothing serious going on in there.

The 5th to 6th is a bit better but sometimes clunks.

The 6th to 5th is still shocking, like someone rear ends you to get going but only from when you do it from around 45mph. If you do it from 60 ish then it's smooth.

2-1 jerk is still there.

Reverse takes about 4 seconds to engage.

Yesterday I was driving about 50mph, went for a kick down and accelerated hard in 5th to the redline, it went for the 6th change but didn't really engage 6th and went back to 5th and it was like in this mid point between 5th and 6th and eventually the trans failsafe came up. Stopped, turned car off and on and carried on as normal. Also this X5 has been used for towing in the past.

[khizman]

Interesting. I have a 4f85 code.

[admranger]

Well, now we have something to work with. What does that code represent?

There is a guy on here who is in the UK that rebuilds/repairs these trannies. RRphil is his screen name. I'd pm him if I were you...

Good Luck!