Weird ZF6 Transmission Issue

[dmbabu]

Originally Posted by robnitro

Most likely fluid, a friend with a 6hp19 described that down shift lag on his 5 series.
He changed it with mercon SP which is what Ford uses in the zf transmissions and it was great.
But look into the seals too, if you're handy or have a good mechanic.

I'll do a fluid and seal change then see if we have an improvement. If there's some, I'll go for an XHP tune to spice things up.

[ard]

OP. Are you the original owner? Do you know how it has been treated? ie maybe it has been abused?



Are you confident that 87k mile number is accurate?!?


I would change fluid, screen/filter and seals- AND NO MODIFICATIONS!!!!- and see if you can return it to 'as new' performance. Only then should you chase after mods. IMO

[robnitro]

Originally Posted by dmbabu

Interesting. I have an F31 with the ZF8 transmission which can disengage (for coasting). Didn't know the ZF6 can also disengage for economy.

Yep. I was watching the fuel rate in bimmer-tool Android app when stopped in D and saw it go from 8mg/R (milligrams per revolution ) to 7.
Releasing the brake, it went back up to 8.
Another time I flipped over to S and shifted to 2 while stopped, same thing, fueling jumped up. (Can't do the disengaging in 2 as it uses a different clutch than 1)
For comparison, switching to N , the fueling goes down to 5 or so. The disengagement uses more fuel than N because the transmission is still active, it just cuts the torque going through the converter by disengaging clutch A IIRC.

I'm running my own xhp custom tune but I never could find the switch that turns on this ability so I never thought I would have it, but it seems it's part of the basic program.
The only odd thing is that sometimes it won't happen at all and I cannot find a pattern it's linked to, whether it be engine temp or transmission temp.

[Greggo]

Ah yes, have seen this before. Repaired several of these transmissions.

You are losing pressure. There are five seals between the Mechatronics valve body and the transmission clutch assembly. These seals need to be replaced. They age, become compressed and the main seal can tear, causing no gear engagement at all.

There are some other symptoms that are indicative of solenoid issues, but sounds more like a pressure problem for you. A hard shift into first gear when slowing to a stop, can be a solenoid problem.

If you have a shop do this, expect a very large bill. Some shops will not do this service and want to replace the transmission, higher profit.

It is a little more fiddly to replace the seals, but not too difficult. A pair of long 90° needle nose pliers are a must! See video link below.

Here is a photo of my last 6HP bridge seal, that would not go into gear at all.




This is the complete kit. https://www.fcpeuro.com/products/bmw...24152333907kt3
Please verify fitment to your particular application. Without the VIN number, I cannot be certain this is YOUR kit.

How to video. Includes trans service and fluid filling procedure. https://youtu.be/2g-5uY_P7uA?si=CI5Dxw4RpRNl6s04



After the third or fourth one, it gets easier.