Transmission Diagnostics

shyne · 09-07-2023, 11:17 AM

Hello! I’ve been dealing with a pesky transmission issue. Before I get into specifics, I’d like to express that I love doing thorough diagnostics as I’m not a fan of throwing unnecessary parts at the car. Diagnosing tips are encouraged but any feedback is appreciated!

The car is a 01/07 build, so it should have the ZF 6HP transmission.
335i/RWD 68k miles
MHD Stage 2, XHP Stage 3

Issues:
-Hard jerk when coming to a full stop. Happens when it goes from second gear to first.
-Can’t do 2nd gear WOT or the transmission gets really weird. Gear shows it’s still in second gear but it actually shifts up to third alone. On rare occasions it’ll downshift to first. (e.g low speed second gear wot)

The car drives fine and shifts every other gear fine. This issue has been persistent since I got the car about 8k ago. The shifts got better after flashing with XHP. Before anybody asks yes kickdown has already been disabled in all driving modes. (D-S-M)

I’ve only ONCE ever gotten a transmission code (4F83 - Gear Ratio Monitoring Clutch C ) and it never came back after restarting the car. To my understanding 2nd gear should be using clutch B.

I’m hoping to hear what you guys think! I was already considering doing a manual swap. A full transmission rebuild will probably lean me over to a swap but would like to get more opinions.

I just want to hear my second gear wot

jadams161 · 09-07-2023, 12:36 PM

I would try first reflashing the Xhp software and then I would also replace the pan/filter, fluid and get the mechatronics seal kit. Most of what you are describing sounds like the bridge seal is bad and the tube seals are most likely hardened too. It is an extremely easy service to do at home.

BRG_N54 · 09-07-2023, 01:08 PM

If you have the same results, before and after a software change, it is most likely a hardware issue. 68k miles is not much, but the age of the rubber in the trans will still cause sealing issues. Replacing the pan and doing the 5 rubber seals and fluid is pretty straightforward. It is recommended to clear adaptations and do the re-learn procedure afterward.

Next step would be the solenoids, I did everything on my 175k '07, just because I was in there. Pan had never been changed, so I assume fluid was also original. Cleaned up the shifting quite a bit, but my car software is all stock so YMMV.

09-07-2023, 11:17 AM	#1
shyne New Member 22 Rep 25 Posts Drives: 07' E92 335i Join Date: Jan 2023 Location: Northern Virginia iTrader: (0) Garage List 2007 BMW 335i [0.00]	Transmission Diagnostics Hello! I’ve been dealing with a pesky transmission issue. Before I get into specifics, I’d like to express that I love doing thorough diagnostics as I’m not a fan of throwing unnecessary parts at the car. Diagnosing tips are encouraged but any feedback is appreciated! The car is a 01/07 build, so it should have the ZF 6HP transmission. 335i/RWD 68k miles MHD Stage 2, XHP Stage 3 Issues: -Hard jerk when coming to a full stop. Happens when it goes from second gear to first. -Can’t do 2nd gear WOT or the transmission gets really weird. Gear shows it’s still in second gear but it actually shifts up to third alone. On rare occasions it’ll downshift to first. (e.g low speed second gear wot) The car drives fine and shifts every other gear fine. This issue has been persistent since I got the car about 8k ago. The shifts got better after flashing with XHP. Before anybody asks yes kickdown has already been disabled in all driving modes. (D-S-M) I’ve only ONCE ever gotten a transmission code (4F83 - Gear Ratio Monitoring Clutch C ) and it never came back after restarting the car. To my understanding 2nd gear should be using clutch B. I’m hoping to hear what you guys think! I was already considering doing a manual swap. A full transmission rebuild will probably lean me over to a swap but would like to get more opinions. I just want to hear my second gear wot Attached Images
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09-07-2023, 12:36 PM	#2
jadams161 First Lieutenant 171 Rep 339 Posts Drives: 2009 E93 335i. 2011 E90 328xi Join Date: Apr 2021 Location: Upstate New York iTrader: (1)	I would try first reflashing the Xhp software and then I would also replace the pan/filter, fluid and get the mechatronics seal kit. Most of what you are describing sounds like the bridge seal is bad and the tube seals are most likely hardened too. It is an extremely easy service to do at home.
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09-07-2023, 01:08 PM	#3
BRG_N54 Second Lieutenant 297 Rep 246 Posts Drives: Green '07 & Arctic '08 335i's Join Date: Jan 2023 Location: Monterey Peninsula iTrader: (0) Garage List 2008 BMW 335i [0.00] 2007 BMW 335i [0.00]	If you have the same results, before and after a software change, it is most likely a hardware issue. 68k miles is not much, but the age of the rubber in the trans will still cause sealing issues. Replacing the pan and doing the 5 rubber seals and fluid is pretty straightforward. It is recommended to clear adaptations and do the re-learn procedure afterward. Next step would be the solenoids, I did everything on my 175k '07, just because I was in there. Pan had never been changed, so I assume fluid was also original. Cleaned up the shifting quite a bit, but my car software is all stock so YMMV.
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