[iqraceworks]

The ZF 6HP21 6-speed AT in my 07' 335i is starting to slip in 5th gear. It's got around 100K miles on it, and I'm running a stage 2+ tune with all the standard bolt-ons.

When it's in 5th gear, as soon as the boost comes on when I'm hard on the gas, the RPMS go up....the car doesn't accelerate, and transmission goes into limp mode (locks in 2nd gear), and throws a 4F850 E-clutch fault.

I've changed the fluid/pan, and replaced the 4 sleeve seals and the double D seal. Didn't fix the issue. The fluid didn't smell burnt..and the pan looked pretty clean.

At this point...is there anything left to try before I start thinking about swapping in a new/used transmission?

Is it worth it to replace the shift solenoids? Try resetting the adaptation? Anything else that could be cause the issue....or is it 100% a problems with the e-clutch frictions?

[Wolf 335]

I have the same issue.

I contacted ZF, and it's likely that one of the cluch packs needs replacing.

Called a reputable transmission place, $2100 for a tranny rebuild this includes new clutches, solenoids, brass bushings, oil, seals.

I been putting it off for a few months now, not sure what to do.

My issues is going into 5th gear. If i drive very very moderately it shifts fine, but if you need to accelerate even the slightest it will throw it into limp mode. Tuning the car off and then on clears the limp mode.

Only way to avoid this, for me at least, is to drive in DS mode.


Dropping $2100 CAD on a 2007 car that is worth no more than $5000....it's a tough decision.

UPDATE: Transmission got rebuilt, clutch pack B and E were worn out.

[marvinstockman]

OK, OK, shift manually with the automatic and go from 4th to 6th, or stay in 4th, that is if you don't want to spend the money on a repair.

[ryan stewart]

Originally Posted by Wolf 335

Dropping $2100 CAD on a 2007 car that is worth no more than $5000....it's a tough decision.

Its not a financial instrument. You're spending $2100 on transportation AND a vehicle worth $5000. Where else are you going to get reliable transportation for that cost?

[iqraceworks]

I have a working transmission I got out of a low mileage 09' 335i.....thinking about dripping that in the car.....it only cost me $300. maybe if I get really adventurous I might try rebuilding a transmission myself. I've rebuilt a few over the years, the really not that difficult... As long as you have the right kind of tools and keep track of all the parts.

[ryan stewart]

This guy did the GM transmission, he might have done the ZF model too. I didnt look but his video was really helpful in working on the GM transmission.

https://www.youtube.com/channel/UCWa...yLyQ7zjW9LF-xg

If I had a spare and a workbench I think it would be a blast to rebuild a transmission given were all locked indoors right now. Not to mention just the achievement when it works.

[smass]

You can send ZF your adaption values, symptoms and code. They will reply with their opinion. If they mention solenoids could potentially fix the issue I would go that route. The solenoids have little screens made of the same material used in the pan filter. In the past when solenoids were over $1000, they were sent out for testing prior to replacement. In most cases, several were found to be out of spec at 100k miles. New genuine ZF solenoids are now under $300. Contact ZF here. https://www.zf.com/corporate/en_de/m...-inquiries.jsp

https://www.thectsc.com/catalog/6-sp...-kits-115.html

[213e90n51]

Originally Posted by marvinstockman

OK, OK, shift manually with the automatic and go from 4th to 6th, or stay in 4th, that is if you don't want to spend the money on a repair.

So its bad to use the manual mode on these transmission? Why stay in 4th ? Only 1234

[iqraceworks]

Originally Posted by 213e90n51

So its bad to use the manual mode on these transmission? Why stay in 4th ? Only 1234

He's saying that if it's slipping in 5th gear.....just skip it. Manually go from 4th to 6th.

Mine only slips if I really honk on it......so it's not really a big deal. I think I'm going to put that uses transmission in my car.....and if it works ok, rebuild the one that's currently in the car.

[tlow98]

Originally Posted by Wolf 335

I have the same issue.

I contacted ZF, and it's likely that one of the cluch packs needs replacing.

Called a reputable transmission place, $2100 for a tranny rebuild this includes new clutches, solenoids, brass bushings, oil, seals.

I been putting it off for a few months now, not sure what to do.

My issues is going into 5th gear. If i drive very very moderately it shifts fine, but if you need to accelerate even the slightest it will throw it into limp mode. Tuning the car off and then on clears the limp mode.

Only way to avoid this, for me at least, is to drive in DS mode.


Dropping $2100 CAD on a 2007 car that is worth no more than $5000....it's a tough decision.

Seems rather reasonable to me for trans rebuild and install. Also, without a working trans the car is barely worth a couple $k.

Compare to the cost of replacing the car and $2100 is 4 months of car payments.

[feuer]

Increased engine HP and TQ output joined by AT tune that increases the pressure will significantly reduced the life of AT. I have two low mileage AT for sale. 2008 88k and 2010 75k. Torque converters too. Never tuned. PM for details.

[iqraceworks]

Originally Posted by feuer

Increased engine HP and TQ output joined by AT tune that increases the pressure will significantly reduced the life of AT. I have two low mileage AT for sale. 2008 88k and 2010 75k. Torque converters too. Never tuned. PM for details.

The reason they increase the line pressure with the performance transmission tunes is to keep the clutch plates from slipping.......more line pressure=more clamping pressure. If anything, it makes the transmissions last LONGER, and/or handle more power without slipping.

But yes..more power and torque is always harder on parts.

I've already got a low mileage transmission ready to put in if I decide to go that route.

[feuer]

Originally Posted by iqraceworks

The reason they increase the line pressure with the performance transmission tunes is to keep the clutch plates from slipping.......more line pressure=more clamping pressure. If anything, it makes the transmissions last LONGER, and/or handle more power without slipping.

But yes..more power and torque is always harder on parts.

I've already got a low mileage transmission ready to put in if I decide to go that route.

Ok, tune out the slippage then. Flash tune that will demand more pressure in 5th gear. Done.

[infinite_creations25]

Originally Posted by iqraceworks

The ZF 6HP21 6-speed AT in my 07' 335i is starting to slip in 5th gear. It's got around 100K miles on it, and I'm running a stage 2+ tune with all the standard bolt-ons.

When it's in 5th gear, as soon as the boost comes on when I'm hard on the gas, the RPMS go up....the car doesn't accelerate, and transmission goes into limp mode (locks in 2nd gear), and throws a 4F850 E-clutch fault.

I've changed the fluid/pan, and replaced the 4 sleeve seals and the double D seal. Didn't fix the issue. The fluid didn't smell burnt..and the pan looked pretty clean.

At this point...is there anything left to try before I start thinking about swapping in a new/used transmission?

Is it worth it to replace the shift solenoids? Try resetting the adaptation? Anything else that could be cause the issue....or is it 100% a problems with the e-clutch frictions?

Would you be able to post your transmission adaptation values using the xhp app? Curious as to what your values look like, particularly for the E clutch

[iqraceworks]

Originally Posted by feuer

Ok, tune out the slippage then. Flash tune that will demand more pressure in 5th gear. Done.

If the problem is with the shift solenoids......then no matter what pressure you throw at the clutch plates, it's getting restricted by the solenoids. Going to replace those first and see what happens.

Also....the pump can only make so much pressure......you only have so much you can get out of it.

[iqraceworks]

Originally Posted by infinite_creations25

Would you be able to post your transmission adaptation values using the xhp app? Curious as to what your values look like, particularly for the E clutch

They are actually not that bad.... nothing is out of range. If I remember right, if you have any over 320-ish.....you have issues. The A clutch is getting close, but the others look fine.

A = 293 mbar

B = 206 mbar

C = 50 mbar

D = -174 mbar

E = 150 mbar

[iqraceworks]

Luckily I have a few options here. After talking to a few guys that specialize in ZF transmissions, it sounds like installing the new solenoids "could" fix the problem...... I'm going to try that first.

If that doesn't fix it....I'm going to pull the transmission that's currently in the car, and install the used one I have. Give it a fresh batch of fluid, new seals, and a new pan filter. Hopefully it will work great and I will be on my way.

But.....if it's got issues too.....them I'm going to buy a rebuild kit and put new clutch plates and seals/bushings in the original transmission. Thank God for YouTube....there are a few videos out there showing a step by step process of rebuilding the ZF tranny's. I think it will be a fun project.

Unfortunately there aren't very many aftermarket options as far as "better than OEM" friction plates for these ZF transmissions. I found one company that makes "race" clutches that are supposed s to hold 1000+ hp....but the rebuild kit alone is close to $2,000. There seem to be tons of guys pushing big power through stock transmissions...so I'm going to give that a shop first. I think I can get new ZF parts for $500-ish.

Keeping my fingers crossed that new shift solenoids fix the problem. I will keep updating this thread as time goes on....

[autoart]

If you do change the trans don't forget the put in a new rear crank seal. while your their. good luck.

[iqraceworks]

Originally Posted by autoart

If you do change the trans don't forget the put in a new rear crank seal. while your their. good luck.

Yeah.....good point.

[Wolf 335]

Originally Posted by iqraceworks

Luckily I have a few options here. After talking to a few guys that specialize in ZF transmissions, it sounds like installing the new solenoids "could" fix the problem...... I'm going to try that first.

If that doesn't fix it....I'm going to pull the transmission that's currently in the car, and install the used one I have. Give it a fresh batch of fluid, new seals, and a new pan filter. Hopefully it will work great and I will be on my way.

But.....if it's got issues too.....them I'm going to buy a rebuild kit and put new clutch plates and seals/bushings in the original transmission. Thank God for YouTube....there are a few videos out there showing a step by step process of rebuilding the ZF tranny's. I think it will be a fun project.

Unfortunately there aren't very many aftermarket options as far as "better than OEM" friction plates for these ZF transmissions. I found one company that makes "race" clutches that are supposed s to hold 1000+ hp....but the rebuild kit alone is close to $2,000. There seem to be tons of guys pushing big power through stock transmissions...so I'm going to give that a shop first. I think I can get new ZF parts for $500-ish.

Keeping my fingers crossed that new shift solenoids fix the problem. I will keep updating this thread as time goes on....

What's your time line on this? I'll wait and see if your issue is solved with solenoids (fingers crossed) before i bring it in for a rebuild.

By the way, what software did you use to pull those adaptation codes? Can it be done with ISTA?

[iqraceworks]

Originally Posted by Wolf 335

What's your time line on this? I'll wait and see if your issue is solved with solenoids (fingers crossed) before i bring it in for a rebuild.

By the way, what software did you use to pull those adaptation codes? Can it be done with ISTA?

One of the techs at Erickson (one of the places that specializes in ZF transmissions here in the US) explained to me how the solenoids work.....they actually modulate the pressure going to the clutch packs by opening and closing super fast...thing milliseconds. He said that when they start going bad, they can't open fast enough....so instead of letting 70psi to the clutch packs, they may only let 20psi or so to them......causing the slipping. He said it's pretty common to have them not output the pressure they are supposed to....so common that they've made it a habit to replace the solenoids every time they rebuild a transmission.

I'm planning on trying to install the new solenoids this weekend if I have the time.

As far as software goes....you can download the xHP app on your phone for free, and it will let you scan for codes and adaptation values. It costs if you want to use one of their tunes, but for just scanning codes, there is no charge.

[Wolf 335]

Originally Posted by iqraceworks

One of the techs at Erickson (one of the places that specializes in ZF transmissions here in the US) explained to me how the solenoids work.....they actually modulate the pressure going to the clutch packs by opening and closing super fast...thing milliseconds. He said that when they start going bad, they can't open fast enough....so instead of letting 70psi to the clutch packs, they may only let 20psi or so to them......causing the slipping. He said it's pretty common to have them not output the pressure they are supposed to....so common that they've made it a habit to replace the solenoids every time they rebuild a transmission.

I'm planning on trying to install the new solenoids this weekend if I have the time.

As far as software goes....you can download the xHP app on your phone for free, and it will let you scan for codes and adaptation values. It costs if you want to use one of their tunes, but for just scanning codes, there is no charge.

Thanks for the info!

I forgot to mention that in my case I hear a whine noise before/during the slippage, are you experiencing the same?