Violent transmission shift: 6HP19 AT xHP Stage 3

Jeffman

Lieutenant
Jan 7, 2017
919
While driving in slow traffic tonight in D mode around 15 mph (2nd or 3rd gear, don’t know) I accelerated slightly when suddenly at around 1800 rpm the transmission shifted so hard and made such a large noise (bang) that I thought I was read-ended. If I were to guess what happened, it seemed that the TCU thought I was doing a WOT pull in manual mode and shifted hard to do a 2-3 or 3-4 shift.

(Car had been driven normally from cold start for about 15 minutes until that point. No dashboard lights or iDrive screen errors. This is the first time something like that has happened since driving with xHP Stage 3 since it was released. 2008 335xi with 66,600 original miles that has never been raced or beaten on, other than numerous WOT 3rd-4th pulls for tuning).
Any ideas, comments, or suggestions as to what caused such a hard and violent shift?
 

Jeffman

Lieutenant
Jan 7, 2017
919
Hows your battery?
New OEM battery 3 years ago. Temp in the 40s. Should be fine. MHD said voltage was 14V immediately afterwards. Curious if you know evidence of poor battery function leading to TCU errors?
 

SlowE93

Sergeant
Jul 2, 2017
378
Mechatronics sleeve failure can lead to tcu errors. Btw, more than likely you have a zf6hp21 not the 19.
 

Jeffman

Lieutenant
Jan 7, 2017
919
Mechatronics sleeve failure can lead to tcu errors. Btw, more than likely you have a zf6hp21 not the 19.
Thanks. Do you know what’s involved in replacing one or more mechatronics sleeves?

And I believe you’re correct about the transmission being a zf6hp21.
 

SlowE93

Sergeant
Jul 2, 2017
378
Hope its a simple sleeve fix for you ! Easy to do . You should do pan and filter (built into the pan), fresh fluid and sleeve. If you are not afraid to take things apart, also do the sleeves between trans and valvebody while you are at it.
 

iminhell1

Corporal
Jun 17, 2018
116
I have a sleeve and was going to change it the last time I did my filter, few months back. But I can't see why I'd need to unless it's leaking. From what I can tell it seals the electrical cables running from outside to inside the trans case. So if it's bad it's going to be leaking fluid. I see no leaks. I can't find it having anything to do with fluid pressure, so it should have no impact on shifting, harshness or anything the like. More likely here is pin corrosion. Unclipping the wiring breaks the corrosion and fixes a problem. The seal is a placebo?


The seal between the VB and case though, that can leak pressure and cause problems. but it requires dropping the VB to replace it.




Battery, Best I can say is I think replacing my battery fixed my trans issues. I can't say for 100% though. I changed up my tune a little around the same time. And I haven't had any track time to really stress the car to make sure it's gone. But I can say the new battery did seem to cure some ghosts the car had.
So just make sure yours is charged good; leave it on a charger for a good day (3A or less). Yes it may have voltage, but what is it under stress?
 
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Jeffman

Lieutenant
Jan 7, 2017
919
I have a sleeve and was going to change it the last time I did my filter, few months back. But I can't see why I'd need to unless it's leaking. From what I can tell it seals the electrical cables running from outside to inside the trans case. So if it's bad it's going to be leaking fluid. I see no leaks. I can't find it having anything to do with fluid pressure, so it should have no impact on shifting, harshness or anything the like. More likely here is pin corrosion. Unclipping the wiring breaks the corrosion and fixes a problem. The seal is a placebo?


The seal between the VB and case though, that can leak pressure and cause problems. but it requires dropping the VB to replace it.




Battery, Best I can say is I think replacing my battery fixed my trans issues. I can't say for 100% though. I changed up my tune a little around the same time. And I haven't had any track time to really stress the car to make sure it's gone. But I can say the new battery did seem to cure some ghosts the car had.
So just make sure yours is charged good; leave it on a charger for a good day (3A or less). Yes it may have voltage, but what is it under stress?
Thanks for your insight. I found this YouTube video by ShopLifeTV which also does a great job of explaining the problem as well as how to do the repair. He seems really knowledgeable about BMWs. If I lived in LA I’d want him to do the work for me.
@doublespaces Is he on this forum? If not, he should be!
 
Last edited:

iminhell1

Corporal
Jun 17, 2018
116
Thanks for your insight. I found this YouTube video by ShopLifeTV which also does a great job of explaining the problem as well as how to do the repair. He seems really knowledgeable about BMWs. If I lived in LA I’d want him to do the work for me.
@doublespaces Is he on this forum? If not, he should be!


Around the 14 minute mark you can see where the sleeve actually goes.

 
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matreyia

Lieutenant
Apr 19, 2017
912
If your sleeve is dry, there is no need to change it.

Welcome to my world.

1. Check your engine mounts. If they are bad, your engine to transmission alignment will be off on high power and cause chassis problems like violent or hesitant shifting. There should be almost ZERO hesitation when pressing pedal to floor. If there is slight hesitation or the car feels like it is saying "oh, you want to go fast" before it jumps...your mounts need to nb e inspected.

2. If mechatronik sleeve is dry and mounts are good, then take out VB, change rectangular seal located between VB and tranny housing, change out 4 plastic tube seals. Change filter pan and fluid and perform sonnax kit update.

If problems still persist, then you looking at internal bushing damage...it or rare that friction packs go bad unless you at 600 hp and above. Same goes for VB.

And do not forget zf driving - programming procedure.
 
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Jeffman

Lieutenant
Jan 7, 2017
919
Awesome, thanks for the good advice, @matreyia.
I haven’t experienced such a violent transmission shift since that one time four weeks ago. I’m certainly well under 600 HP on my stock turbos and 66K original miles.
 

doublespaces

Administrator
Oct 18, 2016
6,937
AZ
Thanks. Do you know what’s involved in replacing one or more mechatronics sleeves?

And I believe you’re correct about the transmission being a zf6hp21.
You have a 6hp21 or a 6hp19Z or 6hp19tu depending on which company's catalog you are looking, all the same transmission.
 

matreyia

Lieutenant
Apr 19, 2017
912
You have a 6hp21 or a 6hp19Z or 6hp19tu depending on which company's catalog you are looking, all the same transmission.
6hp21 is the ZF designation. Whereas 6hp19tu (technisches Update) is the internal BMW designation. They are the identical unit, and beauracratic stubbornness and laziness has kept the same unit with two names, which confuses people.

the 6hp21 and 19tu have 21mm shaft while the first generation has a 19mm shaft.
 
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matreyia

Lieutenant
Apr 19, 2017
912
Thinking about this for a while... i think your trans may be on the way out. Next event may be a gear symbol with gear ratio shift error. This assuming the car will be subjected to logging sessions over the next few months.
 

Jeffman

Lieutenant
Jan 7, 2017
919
Er, thanks...
But saying, “your trans may be on the way out” is a bit general, especially for this forum. Can you please be more specific?
 

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