2007 E70 4.8i - Odd Transmission Issues
 

My E70 4.8i has 81k miles on it, and since I have owned it, the transmission has been acting odd. I am hoping someone that has experienced these issues can point me in the right direction.

Issues before transmission reprogram:
- Especially when cold, the transmission will shift into 2nd fine, and hesitate during it's acceleration period before it shifts to 3rd (e.g. the car is still accelerating, but the RPMs hesitate/stand still) and then it will finally shift into 3rd. Sometimes it will shift into 3rd before this hesitation event, and then once in 3rd, the RPMs will surge hi-low-hi-low, and then shifting from there-on-out is fine.
- When slowing down, and then getting back on throttle in 2nd or 3rd gear, the RPMs will surge up, then down, then up, then finally back down. It's like it's slipping then catching.

After taking it in for a reprogram, all of the above issues are still present, but now it does this:
- When letting off while cruising, the RPMs dip 200 or so, then resume back where they were while cruising.
- If I am off throttle while coasting on the freeway, and quickly get on throttle, the RPMs will surge up past where they were, then quickly settle down to normal.
- I can really feel the 2-1 downshift when coming to a stop. It's feels like someone pushed the brake pedal hard for a split-second, then let off to normal pressure while coming to a stop. It sort of makes your head lunge forward and then back, and then the car finally stops.

I have done a full transmission flush (2 pan drops; ~11 liters of fluid) and a new filter/pan. Oil used was Pentosin ATF1. I didn't notice any change in performance after changing the fluid.

Any advice is welcome. I am really hoping it's not something mechanical. I am a DIYer, but these transmissions are quite complex.

Thanks,
Chase

Drop the mechatronic, take it apart, look for sticky parts, plungers, etc.

Did you download that "BMW ZF_Workbook-transmission-6-8HP.pdf" document? Someone linked it, here or bimmerfest..

edit: here

ZF Transmissions full workbook!! - Bimmerfest - BMW Forums

Do you know if my 2007 E70 4.8i has the 6HP26 or 6HP28 transmission? I am fairly certain it's the 26, but just want to be sure. I am going to do the mechatronic adapter seal, 4 valvebody sealing sleeves, mechatronic sealing sleeve, and the SONNAX zip kit.

26, same as mine.

Thanks. Should be a fun job opening up the ZF.

For those that are curious, parts being replaced are:

24347571211 (transmission valve body gasket)
24347588725 (mechatronic sleeve gasket)
24107519314 (sealing sleeve - 2 required)
24107519315 (sealing sleeve - 1 required)
24107520715 (sealing sleeve - 1 required)
Sonnax ZF6-6R60-ZIP
Pentosin ATF1 (5L jug - to match what's already in there) http://www.pentosin.net/specsheets/pentosin_atf1.pdf

$238 total cost including shipping.

I hope those will solve the problems you're having, but I wouldn't have done a full transmission flush if I had pre-existing issues.

How did the fluid look when you drained it the first time?

Well, it wasn't bad, because about 8k miles prior to that, the previous owners had the mechatronic sleeve gasket replaced. The shop refilled the transmission with Redline D6.

3 different fluids... I guess the theory is why spend $20 a liter fluid when the $7000 trans may be toast??

(Yes, painful I know...)

:(

Very interested to read up on that Sonnax product line... Lets hope you have a solution.

I will report back. From what I have read about the ZF 6HP transmission, is that 99% of issues are due to lost pressure within the clutch assembly do to leaky seals. The part numbers I posted, as well as the Sonnax kit, should fix that.

And yes I'm aware Pentosin ATF1 isn't the "official" Lifeguard 6, but I have yet to hear of a transmission failure due to it. Everyone seems to have great experiences with it in ZF transmissions.

As with engine oils, it is less about 'the oil' than it is about 'changing it'

HOWEVER, with the ATF you dont get a full drain, so you are always going with a 50-50 mix or 40-60, or whatever...I am a very firm believer in not mixing fluids due to differences in the individual stabilizer chemistries. If you do a 3 or 4x "drain/ fill/ drive" then I am less concerned.

For me, I did a 2x...the added $150 just isnt material- easier to stick with LG6