6HP26Z Transmission Questions
 

Have 2 questions on transmission behavior on the 4.8is 2006 build 10/2005. This is primarily wife's car and I haven't driven an Auto transmission long enough on any make to know much about them.

1) after cold start (in the morning or after sitting for a long time), the first upshift, from 1 to 2 is a lurch/grab and you can definitely feel it. Subsequently all gears shift up and down smoothly.

2) after driving for a while, Normal operating temps, almost everytime reverse gear is selected, there is a 2-3 second delay before it engages. In that wait period, giving throttle does nothing(no reverse movement) other than engine rev up. After the reverse gear engages all is well again etc.

I saw there was a TIS bulletin PDF citing a Transmission software flash/update but that is for Build dates up to Aug 05, mine is Oct 2005 build so guess it has that update but not sure any update available after that!

The car has close to 119K miles and is on factory fill as far as auto trans fluid goes.

Are 1 and 2 normal or symptoms or some issue around the corner? I will have a trans shop run some diagnostics but before paying want to find out from the forum as well.

The first shift on an auto trans is temperature dependent. If it is cold outside, the computer will delay the shift so the engine would rev higher to pump fluid through the valve body because at low temperatures the ATF shrink/contract in volume.

Thanks upallnight. Good point.

I had the same problem with my 6hp26 ... fixed by dropping the pan, changing the filter ( and mechtronic sleeve while you are there ) and then fill it back up ( I used RL D4 ATF )

Then I did another fluid dump and refill in 20k miles and it has never shifted irregular again.

Temperature has nothing to do with it... the filter is obviously clogged after 100k miles

Thanks @BigBlack48is, so
the Mechatronic sleeve is part 24347588725 - #1 here? 16$ local dealer
And the trans filter value kit is part 24152333899 which basically is everything here minus the pan. 90$ local dealer

As for the fluid, I am either thinking of replacing same volume with fresh LifeGuard 6 and top off till fill hole at correct temp. Will have this done at a local reputed transmission shop.

This post is correct on the first shift of the day on a cold start. The 2 & 3 gears upshifts will be delayed until 3,000 RPM regardless of load.

The Original Poster (OP) appears to have a larger problem (greater) that might be fluid/filter related, so a trans service is a good starting point, especially if the fluid level is under question. There is a whole lot of debate on trans services on this forum. Fluid/filter changes, fluid level corrections, and software updates have helped reduce or solve lots of issues.

I wonder if moving to Dinan software helps/hurts the update issues?

Steve, the Dinan Tranmission flash is only for Pre-LCI 4.6is I thought? I checked Dinan website and didn't find anything Transmission related to 4.8is. Link

Ven,

I would crawl under there and check out the bottom of the transmission. if it is a metal pan ( like mine ) you will just need part 7 & 6. If it is a plastic pan ( doubtful, because I have only seen it on other vehicles with the 6hp26 ) you will need the filter / plastic pan combo.

It's worth checking before you order any parts. The fluid choice is totally up to you. The only reason I went with D4 was because I was lucky and got a really good deal on a few cases of it and after calling RL directly and telling them my application. They stated D4 was just as good as LF6 ( which is actually made by shell and labeled by ZF ).

Just because a shop is reputable doesn't mean mistakes can happen... and the only way to avoid that costly mistake, is to do it myself!

Hope the info helps :)

Yes, gasket is 28 and filter is 45, so few bucks cheaper than the kit.

I will check the underbody to confirm I have metal pan. As per Realoem, looks like I have metal pan though

Transmission symptoms can be misleading. I would take it to a well recommended transmission shop that has experience working on BMW transmissions. Not saying cold weather couldn't contribute or a fluid and filter won't cause your symptoms but I wouldn't draw any conclusions until after that tranny shop diagnosis. Probably not cold where you are this time of the year and quite often when a transmission shows symptoms a fluid change is not the problem.

Here's a link to some symptoms and causes: http://www.xoutpost.com/bmw-sav-foru...s-summary.html

I suffer the exact same symptoms as you have described. Cold start results in harsh shift from 1st to second, reverse slow to engage and while cruising at urban speeds with slight throttle application, the trans 'hunts' between gears (almost like engine is 'missing' a little).
I've researched this until the cows come home... I believe there is a trans 'flash' that can be done to rectify these problems. I don't know much more than this though and would be in your debt if you find out what's involved, where to obtain this flash and how to undertake it.
I've serviced the trans and drained fluid out a second and third time. There was no evidence of any metal in the pan or on the magnets, other than 'normal' grey wear material (a modest amount). The transmission does NOT slip, changes well and operates beautifully in sports mode and auto, with the exception of the 'hunting' when gentle throttle application is applied.
I believe that these symptoms can occur after your vehicle has suffered a dramatic voltage drop, like your alternator has died or you've replaced the battery recently (and had no source of power attached for a while) or so I've read. The previous owner of my car replaced the alternator about 2 months prior to me buying it, so I think this may be the problem and a 'flash' is supposed to fix it. Not sure where to get this so called 'flash' or even if my PA soft tool is suited for the job - I imagine you need something a bit better. I'll be keenly following this post, as I'm aware of at least one other owner who is suffering the exact same symptoms and would also like to solve the problem. TIA.

I had the harsh 1-2 shift with a cold transmission, but no other symptoms aside from that. I bought mine with 180,000km and it had original fluid/filter. I did both (plus the sleeve while I had the pan off), and 45,000km later it's still fine. I plan another fluid/filter swap at 230,000km. I used original BMW filter, fluid, gasket along with new pan bolts.