[JustinCredibleM]

I tried doing a search on this, but I keep getting different results when trying to find the max torque capacity for this transmission. Does anyone know how much power this transmission is capable of? I saw results ranging from ~350wtq to as high as 500wtq.

Wikipedia shows that it can support ~450NM assuming its the HP45 seires? http://en.wikipedia.org/wiki/ZF_8HP_...F_8HP_variants

I saw the Burger Tuning 435 making around 450wtq on their setup so I assume it has a high rating, but I just want to know for sure.

[Greenkirby21]

yup I believe you are correct. According to real-oem, the M235i manual and auto are the same model # as the F30 335i.

Manual max is 470 nm
Auto max is 450 nm

[JustinCredibleM]

Originally Posted by Greenkirby21

yup I believe you are correct. According to real-oem, the M235i manual and auto are the same model # as the F30 335i.

Manual max is 470 nm
Auto max is 450 nm

That should convert to around ~330 foot pounds though and the car is rated as such from stock. It seems a little odd to me if the capacity is already stock though.

[M.barnes]

Yeah the gearbox is already at its max recommended torque

[Brings]

Kind of scary to hear that considering the N55 can generate tons of extra torque just from breathing on it at a different angle...

[Greenkirby21]

Ya.. How do the current F series car last so long with JB4, downpipe, and all the other stuff?

[ska///235i]

I highly doubt anybody is really pushing all 360hp on the streets...its all for bragging rights

Their waterpump or some other stuff will get blown before they can use all that HP and cause the tranny to fail

[JustinCredibleM]

Originally Posted by ska325xi

I highly doubt anybody is really pushing all 360hp on the streets...its all for bragging rights

Their waterpump or some other stuff will get blown before they can use all that HP and cause the tranny to fail

How does that work with F-series cars with same tranny making 400wtq+?

[ska///235i]

I was trying to say other things will break down before the tranny will

[M.barnes]

Originally Posted by JustinCredibleM

How does that work with F-series cars with same tranny making 400wtq+?

How does it work or how long will it work?

Quite possibly the box can handle more, personally I don't fancy trying while I have warranty

[255zr]

I was looking at a Dinan tune as it maintains the original BMW warranty. Would be surprised they would let you increase the torque to around 400lb/ft yet maintain the warranty if the tranny tops at 330lb/ft

[thomps]

Really, really curious to hear an informed opinion on this. The torque ratings are especially strange given the tendency of BMW to underrate these cars from the factory. It's really hard to believe BMW would allow a car to leave the factory with power above and beyond the transmission's true limit.

If the auto is anywhere near maxed out from the factory, that's enough to scare me into the manual trans despite the fact that my circumstances pretty much require an auto. And I remember some discussion that the manual trans had inherited some parts from the M3/M4, which was comforting, but if the manual trans is also nearly maxed out from the factory, I'm afraid I'll have to forget about the M235i altogether. Again, I doubt this is the case, but I'm not trying to be the guinea pig.

I did some research, especially with respect to the M135i, and there's been lots of talk (see threads below) but no real consensus.

http://www.babybmw.net/viewtopic.php?f=74&t=48109

http://www.f30post.com/forums/showthread.php?t=937956

http://f20.1addicts.com/forums/showthread.php?t=837879

http://f20.1addicts.com/forums/showt...5#post14845115

[255zr]

Doesn't answer your question, but if I do a tune (Dinan) that doesn't void the warranty at that point it's not my problem anymore

[ShlemonboostedM]

Pushing about 400-450lbft in fbo f30 on 8zf for 8 months already not a single problem .. Those trannys are over build ... Read a post on 3/4 f30/32 theirs zf rep. Telling that trannys are way overbuild and can handle much much more the. They were design for .. Haven't heard a single official tranny break down yet ..

[ska///235i]

Originally Posted by thomps

Really, really curious to hear an informed opinion on this. The torque ratings are especially strange given the tendency of BMW to underrate these cars from the factory. It's really hard to believe BMW would allow a car to leave the factory with power above and beyond the transmission's true limit.

If the auto is anywhere near maxed out from the factory, that's enough to scare me into the manual trans despite the fact that my circumstances pretty much require an auto. And I remember some discussion that the manual trans had inherited some parts from the M3/M4, which was comforting, but if the manual trans is also nearly maxed out from the factory, I'm afraid I'll have to forget about the M235i altogether. Again, I doubt this is the case, but I'm not trying to be the guinea pig.

I did some research, especially with respect to the M135i, and there's been lots of talk (see threads below) but no real consensus.

http://www.babybmw.net/viewtopic.php?f=74&t=48109

http://www.f30post.com/forums/showthread.php?t=937956

http://f20.1addicts.com/forums/showthread.php?t=837879

http://f20.1addicts.com/forums/showt...5#post14845115

Keep in mind bmw doesnt built these trannies, they're from 3rd party

[thomps]

Now that people are actually getting their hands on the car and modifying it, I'd like to keep this thread relevant.

Anybody modding ZF8-equipped M235i's yet? Problems? (I know, it's still early-- knock on wood)

[PeteA]

ZF8 should be fine from a reliability standpoint.

Generally automatics better than the manuals at withstanding torque over time as they don't wear like clutch plates would. However one perspective is that a clutch plate is easily replaced/upgraded...

The only transmission that has been known to slip when tuned on the N55 is the DCT.

The ZF8 speed on a diesel variant seems to have a torque limit of 500Nm which is the same gearbox...8HP45.

[DanG]

Originally Posted by 255zr

Doesn't answer your question, but if I do a tune (Dinan) that doesn't void the warranty at that point it's not my problem anymore

Actually you are mistaken. Dinan upgrades do void the BMW warranty. Dinan warranties the parts until the BMW warranty would have expired.

[Bruce GT3]

Guys, don't forget that the non-USA market has been running the same 'box in the "same" chassis for more than 2 years in the M135i.

I've been running 395 bhp and 450 lbft (approx 610 Nm) of torque through the ZF-8HP45 on my M135i for around 6k miles without any issues.

If it does blow up it's down to me and that's a bridge I'll have to cross when I come to it. But I'm happy that ZF will have overspecc'ed the tranny anyway. ZF have a whole range of 8HP trannies as a modular system that go up to the mighty 8HP90 that's fitted to the Bentley Continental GT and is good for 900 Nm, so I'm confident that it should be possible to upgrade the transmission when required...

http://www.zf.com/media/media/img_1/...Produkt_EN.pdf

[adrianv]

Well, I lot of this is speculation, but I can make some observations:

The "launch control" on the sport auto is nothing more than standing on the gas and brake, loading up the torque converter, and releasing the brake. This is obvious from observing what the car is doing when using it. There is no observable difference between activating launch control and using the same proceedure of brake-launching in D and comfort.

Historically, this technique for launching automatics has been around for decades. It is extremely hard on the torque converter, but it is a very effective technique.

This is the only automatic I have ever seen that the OEM sanctions "abusing" the transmission this way and calls it "launch control". This has the implication that BMW will cover a transmission failure due to using launch control under warranty.

BMW would not recommend using the transmission this way unless there was significant headroom in the torque handling of the transmission. Automotive OEMs are extremely risk averse when it comes to the actuarial analysis of their warranty cost and exposure.

All of these observations together make be believe that this particular transmission is very over engineered and has an enormous design headroom in its torque handling capability. It wouldn't make any logical sense for BMW to implement a launch control in a way that is literally the most abusive thing you can do to a traditional automatic if it that was not the case.

[PhilAnthony]

Not going to lie... I have a 2013 335IX F30 with ZF8 and after installing ER dp and JB4 -- I was running maps 1,2, 5, and 7 with 100 octane and even some E20 to see how it responded. I was loving hthe beta map 5 that was release for the Fseries..

Until about 2 months ago, I had no problems. Then on a cold morning, I went full throttle on Map 2 (with dp, same setup dynoed at ~360whp and 450wtq) I ran into some slippage in the transmission. It would NOT catch gears from 1-2, 2-3, even 3-4 at heavy throttle shifting at its major torque making rpms (like 3500-5500)... I was stunned because I had not read one single complaint. The car would accelerate like a rocket but when shifting it would throw you forward because it was like hitting the breaks. It took very long to shift into the next gear and the momentum was broken. It was not normal and it was very much a fucking bad shift. I was so mad.

I was fairly certain that the tranny was overbuilt but once it started to slip I kept trying to turn off the JB4 and engine to see if it was a computer error. NO check engine light came on and NO shadow codes or tuner codes when read with BT Scan Tool. The transmission wasn't warning me or the computer about this.

I was due for an upcoming oil change so I removed the dp and the JB4.... told the service about the problem amongst other things. The water pump would turn on and continue to run after long drives and the oil gauge would note that oil was low (damn N55s suck up oil) and the car would also run a bit hot. I continued to feel the slip (maybe doing it too much .. like a bad scab on the elbow that you can't stop picking at). I feel that the clutch packs are toast and I would love to see the tranny fluid.

Not sure what BMW will be able to do for me since there is no check engine light. I am hoping they check fluid and other things. The good thing is after I would turn off the JB4, it would NOT slip anymore.

After noticing that the slip only occurred with the JB4, I figured it was most definitely due to the torque and stress on the tranny. I read someone's post on a thread I started about this problem and he said something along the line of "I like to think that the problem already existed and was exacerbated by the mods" ... so maybe the transmission was faulty from the start and it was made more blatant with the tune and dp.

I dropped my car off today actually. Got a loaner car for now. It is all stock and codes deleted (tuner codes like O2 sensor, blowoff valve jammed close, MAF problems). I hope they find it to be something simple like low transmission fluid or something (i am no mechanic lol). I think I remember seeing some fluid that had leaked from underneath and left its mark on the removable undercarriage that covers the tranny and turbo/cat. Maybe something blew?

Will update you on what happens. It will be hard to diagnose the problem if they cannot reproduce it (no more JB4).

EDIT: from adrianv's post ... I may have done a good amount of launches using the brake and accelerator with the jb4 active ... could the torque converter be "worn out" or "bad" from these launches?? I cannot recall how often I would do them because I only had the tune on for about 5 weeks and I have had it off for about 3 weeks.

Thanks.

[JustinCredibleM]

@PhilAnthony - Considering how much torque these cars make down low and almost full torque at 2,000 RPM, you probably loaded up the torque converter too much with your launches. I don't plan on ever launching considering the amount of torque it is generate with the JB4 active. I am curious how BMW will handle this, since I would be pretty sad if my transmission started doing that. But the BMS 435 makes 450wtq and they haven't mentioned any issues (yet).