[mcmastah]

Hi all,

I recently bought a 2008 335i 6AT w/ 87kms on it a few months ago. I was driving it like a madman for 2 months and everything seemed to be in good order.

I flashed the car 2 weeks ago via MHD to stage 1/1+. Since then, the car has slipped about 6-7 times while flooring it from 80-100km/h. I want to say the slip is occurring from 5th to 6th. I think all the other gears are fine?

Each time the car slipped, a yellow cog (transmission?) warning light came on and the car went into limp mode and was stuck in one gear. I had to power cycle the car to drive it normally.

I'm surprised its slipping like this given its only stage 1, is this normal behaviour?

I'm not sure what's going but if anyone can point in the right direction it would be a huge help. I'm not sure what to do next, should I install xHP and see if that resolves the issue? Or should I do a full transmission service ala drain & fill?

I've flashed back to stock in the meantime, and its driving fine, even aggressively. have I done major damage to the trans via the 6-7 slips?

Thanks in advance.

[mcmastah]

Update:

This is the code that's coming up upon scanning the car:

4F8A (4-5 ratio monitoring code)

[Sgop335]

Not normal behavior and depends on whether the transmission has been serviced.
The basic service is pan and fluid, which replaces the filter that is part of the pan. That may or may not fix.
Next is the mechatronic seal, which could be torn.
Next mechatronic sleeve, but only if there is an external leak. This one is a bear.
Next are the solenoids.

[mcmastah]

Originally Posted by Sgop335

Not normal behavior and depends on whether the transmission has been serviced.
The basic service is pan and fluid, which replaces the filter that is part of the pan. That may or may not fix.
Next is the mechatronic seal, which could be torn.
Next mechatronic sleeve, but only if there is an external leak. This one is a bear.
Next are the solenoids.

I took it to 6 or 7 different shops and half of them won't do the transmission service as they say it make the problem worse or cause new problems...

I was quoted $700 for the pan & filter change using genuine ZF parts; but like you said, this may or may not work. I was quoted $2800 for a full rebuild, but I feel that's too drastic to go from 0-100 right now. Mind you these are Canadian prices.

I'm stuck on what to do next; its frustrating this issue isn't present when the car is on stock power. Sadly, the hard earned $1500 I spent on buying/installing performance parts and the MHD tune seems like a sunk cost at the moment.

Has anyone had this issue and resolved it with a full transmission fluid service, or am I better off putting the $700 towards a full rebuild?

[Sgop335]

The zf 6hp is pretty good but does need service. A diyer would look at the mechatronic seal to check if its torn. If not, a full service may be required. Not sure if a shop can look systematically

[leif20]

https://www.e90post.com/forums/showt...php?p=24913618
https://www.e90post.com/forums/showthread.php?t=1627530


mcmastah

Have you isolated whether your fault is slipping between gears, or in a particular gear? I drove my car with no issues for a while, but since i was driving it hard the issue surfaced after about a year. I think that your tune putting more power through the trans probably caused it, but if you're careful with your driving and address the issue quickly, likely there will be minimal wear to the trans. The first thing i would do is revert the tune and drive like there's an egg between your foot and the gas pedal.

I called around various shops in the GTA and was told the same as you were, $2500-$3000 for transmission rebuild. The cost was the reason I went DIY, I figured that replacing the solenoids and seals would at least provide those new components in the event the transmission did need a rebuild.

My recommendation for anyone experiencing trans slip issues with a higher mileage E90 and ZF transmission is to replace the solenoids. While you've opened it up, do the finger seals, bridge seal, and mechatronic sleeve. Make sure you disconnect the battery when doing this service and be very careful not to touch the mechatronic pins.

The transmission service is simple in many ways, but also quite tedious. Plan for it to take one full day, maybe two days if it's your first time. Make sure you have all the parts ready to go, receptacles to catch the old fluid, cardboard all around, a new pan and filter assembly, the correct solenoids, 9L of fluid (better to have a little extra). To get the right level in the rans the car has to be level. you can use the door sills as longitudinal level, and the trunk surface for lateral. It's also VERY important to use INPA or similar program to reset transmission adaptive memory, and then perform the break-in procedure which is best done early in the morning or very late at night on straight, rural roads with minimal traffic.

I also bought 20 new pan bolts and a 3/8in 50-250in-lb. torque wrench for reassembling the mechatronic, and torquing the pan bolts.

[mcmastah]

Originally Posted by leif20

https://www.e90post.com/forums/showt...php?p=24913618
https://www.e90post.com/forums/showthread.php?t=1627530


mcmastah

Have you isolated whether your fault is slipping between gears, or in a particular gear? I drove my car with no issues for a while, but since i was driving it hard the issue surfaced after about a year. I think that your tune putting more power through the trans probably caused it, but if you're careful with your driving and address the issue quickly, likely there will be minimal wear to the trans. The first thing i would do is revert the tune and drive like there's an egg between your foot and the gas pedal.

I called around various shops in the GTA and was told the same as you were, $2500-$3000 for transmission rebuild. The cost was the reason I went DIY, I figured that replacing the solenoids and seals would at least provide those new components in the event the transmission did need a rebuild.

My recommendation for anyone experiencing trans slip issues with a higher mileage E90 and ZF transmission is to replace the solenoids. While you've opened it up, do the finger seals, bridge seal, and mechatronic sleeve. Make sure you disconnect the battery when doing this service and be very careful not to touch the mechatronic pins.

The transmission service is simple in many ways, but also quite tedious. Plan for it to take one full day, maybe two days if it's your first time. Make sure you have all the parts ready to go, receptacles to catch the old fluid, cardboard all around, a new pan and filter assembly, the correct solenoids, 9L of fluid (better to have a little extra). To get the right level in the rans the car has to be level. you can use the door sills as longitudinal level, and the trunk surface for lateral. It's also VERY important to use INPA or similar program to reset transmission adaptive memory, and then perform the break-in procedure which is best done early in the morning or very late at night on straight, rural roads with minimal traffic.

I also bought 20 new pan bolts and a 3/8in 50-250in-lb. torque wrench for reassembling the mechatronic, and torquing the pan bolts.

Hi Leif20, my problem appears to be when shifting from 4th to 5th. Regarding reseting the trans adaptations; I'm reading conflicting opinions. Some say to reset after the fluid service and others say not to touch it unless the trans was rebuilt.

[Bimmer_Ross]

xHP is a must-have for us!

What I've seen from my own experience is that there are usually two main culprits:

Low Transmission Fluid: This is super common, especially if you've recently had your transmission serviced and it wasn't filled up all the way.

Too Much Torque: Our automatic transmissions can only handle so much torque before they start to slip.

You'll feel the difference immediately when you switch between its stages.

Stage 1: Never loaded
Stage 2: Small difference, and slips if I go WOT under 40-50 mph
Stage 3: My current setting and personal favorite. No slip on wide-open throttle (WOT) runs
Stage 4: Unless you're hitting the race track, I'd probably steer clear. It keeps the RPMs really high, which gets old super fast in daily driving.

[leif20]

Originally Posted by mcmastah

Hi Leif20, my problem appears to be when shifting from 4th to 5th. Regarding reseting the trans adaptations; I'm reading conflicting opinions. Some say to reset after the fluid service and others say not to touch it unless the trans was rebuilt.

Resetting transmission adaptives are necessary when any component of the transmission fluid path changes, including the fluid. It won't fix the slip issue by itself.

[mcmastah]

Originally Posted by Bimmer_Ross

xHP is a must-have for us!

What I've seen from my own experience is that there are usually two main culprits:

Low Transmission Fluid: This is super common, especially if you've recently had your transmission serviced and it wasn't filled up all the way.

Too Much Torque: Our automatic transmissions can only handle so much torque before they start to slip.

You'll feel the difference immediately when you switch between its stages.

Stage 1: Never loaded
Stage 2: Small difference, and slips if I go WOT under 40-50 mph
Stage 3: My current setting and personal favorite. No slip on wide-open throttle (WOT) runs
Stage 4: Unless you're hitting the race track, I'd probably steer clear. It keeps the RPMs really high, which gets old super fast in daily driving.

Wont xhp be just a band aid fix for my car that's only running a stage 1 tune? Im thinking it shouldn't really be slipping at all under the minimal hp/tq gains...if this was the case w/ everyone's car slipping on a stage 1, MHD & tuners alike would be out of business.

You could be right about the transmission fluid, I'm not sure if the previous owners ever changed it as BMW says it should last the 'lifetime' of the vehicle

[Bimmer_Ross]

So right now, I'm running JB4 Map 2, but I switch over to Map 5 when I'm on ethanol. Usually about 6 gallons of E85 mixed with 8 gallons of 93 octane. I'm trying to full send my stock turbos and go big single, so I'm pushing them hard, all the way up to 21 psi! It's been a blast so far, easily gapping 5.0s, SSs, and Scat Packs. I'm just telling you all this to give you an idea of where my car's at speed-wise since I haven't gotten it on the dyno yet.

I never had traction issues until I really cranked up the boost. I dealt with it for a bit, but then I went full X-delete just for kicks. I snagged xHP mostly because it sounded cool, but holy cow, it's a complete game-changer. Seriously, no exaggeration, I can do short pulls (20-100 mph) against Hellcats and actually hold my own! I'm pretty sure it's almost entirely thanks to the transmission.

Additionally: Your trans slipped when you went WOT, which means the Auto clutches were slipping. xHP increases the clamp force which eliminates that. So as far as "band aid" it depends on how you look at it. a true fix would be to do a complete manual swap. personally, im good with my auto. pedal shift with xHP is also a lot quicker.

[smass]

I was where you were a year ago. I wasted a lot of money on fluid, solenoids, seals, new pan, XHP. The new fluid actually made the slip worse. I ended up doing an 8 speed swap for much less than a 6 speed rebuild. Best mod ever. Feels totally factory.

[ptpending]

so the key thing is that 6hp19 6hp21 is weak for 335
and anybody doing tuning is killing it much faster
if you want stage - do DCT or 8HP swap

[Jeffman]

“Maintenance before mods” - always remember this.

FWIW:
I’ve owned my 2008 E90 335xi 6HP21 since new. Self tuned the engine (21 psi max boost). At 50K miles preventative maintenance (ATF fluid change plus new filter). Running xHP Stage 3 since 63K miles. At 71K miles I noticed some transmission slipping and did the full 6HP21 maintenance: fluid, pan/filter, mechatronics connector sleeve, bridge seal, solenoids all replaced with ZF and 7.7 liters of ZF Fluid.
Reset Transmission adaptations.
Today the car is at 77K miles and still running like a champ!

Recommendations:
1. Do the AT maintenance - regular fluid and filter/pan changes every 60K miles. Do the seals / mechatronics as soon as you feel slipping.
2. Get xHP
3. Enjoy!

[Sgop335]

Exactly and definitely not DCT.

Mine is at 170k