ZF6 after accelerating up hill takes a while to change into 4th

[Puffwagon]

All good mate, hopefully this gets it sorted and it's smooth sailing from here on out.

[Nick_is_not_sus]

Hey a bit of an update...arrived at work at 7.30am manged to have a free hoist at lunchtime ( checked pan it was stone cold ) and threw it on the hoist with the car running you were 100% right, it took another 5-600mls of trans fluid .. gearbox is alot smoother still hangs in third after big hill but its improving... I have a Xtool PS80 at work and did a full car diagnostics no codes what so ever apart from p0420 which will be second o2 sensor from cat removal (not sure if I can delete that secondary sensor without messing with the tune?)..... I was actually really tempted to reset the learning on the TCM ... but while I was there I calibrated my speedo since I'm running 245 35 20s ....came to the conclusion that I'm going to drive the car around and put a few hundred more kms and drop the fluid again, I just think it was so contaminated (black).. I may be wrong but I dont think the trans has ever had a service it had the original green gasket I wouldn't think it would be reused right? .... I'm keeping updates going just so if anyone in the future has something similar

[Puffwagon]

You can turn off the second O2 sensor in the tune but if it's just a code and not a MIL I would leave it.

 

If you can see the adapts on the clutches with your scan tool, there's 5 of them, you'll have an idea of the condition of the box. I'll post a pic of the stock 3=>4 shift pressure in mbar, the adapts will add or subtract from that. While the adapts generally only add or subtract a few hundred mbar at most, you'll see this is actually a significant amount of pressure, especially at lower loads. If it's already adding pressure, which it will be as it's a bit old and worn, a reset will make the box slip into the next gear and flare between changes. It may even flare like a mofo and bang into the next gear like a clutch kick if you gave it the boot and shift it in manual mode, mine has done that after a reset. You can do a reset if you want to see for yourself, just be prepared to drive gently for a while until it's back to normal.

 

I think a few weeks of normal driving will have it sorted. Leave the shifter in the normal auto driving position the whole time so it can do it's learning thing.

 

Just a thought, if the box is adding pressure everywhere then the downshifts might also have more pressure and might want to hold the gear...dunno I ain't a trans expert

 

[Nick_is_not_sus]

Bit of an update, still doing it not as bad I'm going to change the fluid agin soon. I think this time for piece of mind ill drop the mecatronics unit out and replace the seals and hopefully I should be able to inspect the internals a little more... another thought thought I had was how temperamental are the transmissions when it comes to rolling circumference? The factory option for my car is 245/40/18  I am running 245/35/20 stretched onto a 20x10 all round which ends up being a 4% difference in rolling circumference

Edited 29/10/23 10:55 PM by Nick_is_not_sus