6HP26Z Transmission Questions

[Ven]

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.

[upallnight]

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.

[Ven]

Thanks upallnight. Good point.

[BigBlack48is]

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

[Ven]

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.

[StephenVA]

Originally Posted by upallnight

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.

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?

[Ven]

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

[BigBlack48is]

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

[Ven]

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

[bcredliner]

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.