I just remembered that when I had a problem with adaptations I was able to get help directly from ZF. I will send you the contact info my PM.

TBB

 

2003 all had the ZF. It was the first year they were used.

TBB

 

I have a ZF 6HP26 tranny for sure.

 

I hate to tell you but a slipping transmission is usually a sign the clutch plates are worn and the transmission needs a rebuild.

in the old days many of us experienced a failing transmission after a fluid and filter change. And while we might not have any actually root cause evidence to prove it, the majority anecdotal consensus among mechanics was that the fluid change helped speed up the death of the transmission.

The reasoning being that a transmission works off a number of friction clutches which need to stick together in order to let various assemblies rotate inside the transmission. As many miles Are put on the transmission, those clutch plates wear down and the remnants of the clutch plate material is deposited in the transmission fluid. The transmission continues to work because the remaining friction material on the clutch plates still has enough grab to rotate the assemblies because the transmission fluid carrying the clutch plate debris helps the worn clutch plates to function. But after flushing or changing the fluid you have removed that clutch plate residue from the fluid so now The clutch plates wears out at an accelerated rate causing the death of the transmission.

i had it happen and I am really hesitant to change transmission fluid but will if it looks or smells really bad. But even then I make sure I leave some old fluid in the lines and torque converter for some help

 

Google Transmission flush kills transmission

https://bobistheoilguy.com/forums/threads/changing-atf-kills-old-transmissions.145201/

https://mechanics.stackexchange.com/questions/17217/any-truth-to-the-myth-about-changing-transmission-fluid-in-older-vehicles

 

Do you think what would happen with even half or less than that amount the fluid being changed? I understand the most important of the clutches in these transmissions is the E clutch and the one to first wear out. I would never suggest an actual "flush" on an older transmission.

TBB

 

Here is a video showing the car idling in Park.
Engine has not warmed up yet.

Listen to the sound: You can hear the periodic fluctuation in the sound of the idle.

initially it's pretty fast.when I put the car in either reverse or drive, it will lunge and jerk based on the frequency of this fluctuation.
I will put up some more videos and tell you about a little experiment i did today.

 

First movie is idling captured from under the car, in park.
I then put the shifter in drive, with foot firmly on brake.....and in reverse (third movie).

 

I decided to experiment with the car.
This problem was first encountered during our unusually cold winter.
A couple of times, the car drove fine when fully warmed up.
So after I made these videos, I let the car idle longer, even revved up the engine to 1000- 1500 rpm
in park and also in neutral.

As the car was getting warmer, the fluctuation in the idle became less frequent.
when I put it in gear, it jerked a lot less.
I only moved a few yards in my carport, did not really drive around.

Checked the external temperature of the transmission pan and the front of the transmission housing showing 70 Celsius on my infrared thermometer.
I then counted the seconds between jerks "the fluctuating whiny sound" and it was 41 seconds at that point!

In the video I took before it was practically at every second or so!

Conclusion:
Warming up helps.

Is it the engine or transmission or torque converter temperature that makes the difference?
What does this mean anyway as far as the origin of the problem?

 

Never heard sounds like that before, but maybe others have. Have you tried the stethoscope test or even with a piece of wood or metal against your ear and put it on the tranny or the converter and see how it sounds when the noise is happening or perhaps isolate it?

You may have seen this, although I will warn you these guys are obsessed with the valve body, but maybe it gives you a hint to something else.

https://www.bavlogic.com/?p=3738

Did you walk through the Jag matrix that I posted on the tranny. That is a step by step approach.

Also I would not be testing in sport mode which I saw was lit on yours. Put it in normal. If you can't get it to work there, altering the shift points and holding it in the lower gear may not give you the best testing environment.

TBB

 

Wheel speed sensors can cause gearbox to lurch and jump gears if not working correctly

 

I only left it in sport mode to observe the sport indicator to blink which was really odd.

 

I decided to check certain components while waiting for the new iCarsoft scanner to arrive.
The ignition coils and spark plugs were replaced a year ago along with the knock sensor and valley hose.
Because of the weird periodicity of the problem and the fact that it was present during idle, I still wanted to look at the possibility if it was somehow ignition related.

 

So checked all the spark plugs and found that they had some burned residue on them and appeared under-torqued.

I remember tightening them a 1/2-to 2/3 turn past finger tight but not actually torquing them.

(this may not have been enough) I was more afraid of over tightening but then under torquing is also a problem.

This time I cleaned all plugs and torqued them to 16 ft lb.

Ended up replacing #8 because it appeared to have the worst contamination.


Eventually planning on replacing the valve cover gaskets and the seals around spark plugs.

No oil in the spark plug wells but there was oily crud in spark plug threads.



Restarted the engine and the fluctuating idle went away!

No jerking or lunging in gear either.



Received the new scanner the next day and scanned for codes, took the car for a 2 mile test drive.

The transmission shifted well but this was only in the neighborhood and not highway driving.

so I got home and scanned for codes.

P0730 (incorrect gear ratio) was stored.



I cleared it and did not reappear after a second test drive lasting 25 miles including some suburban/rural highway (not interstate) driving.

During the second drive, there were harsh up shifts (twice) what looked like from 3 to 4.


No new transmission warning lights or codes appeared.

However, the ABS warning came up when I pulled out of the driveway.
This had occurred before, during backing up and turning the steering wheel like when making a u-turn.

These codes codes are present:

C1165 wheel speed rear right input-circuit failure

C1175 wheel speed rear left input-circuit failure

C1155 wheel speed front left input-circuit failure

also

U2523 CAN message timeout from engine control unit.

 

So it looks like most of my recent transmission issues were ignition related.
There were no misfire codes just the weird idle sound, which led me to the initial rabbit chase and then the eventual solution.
I went on to replace both valve cover gaskets and spark plug seals hoping this would solve the fouling issue.

With all spark plugs cleaned (one replaced) there is no lunging in gear and the shifting is becoming smoother by each drive cycle.
Drove the car very little during this time, I'm trying to tackle the maintenance and repair items one by one.

No more abs codes!
Both rear wheel sensors and the front left hub (comes with new sensor) were replaced.
Opted for Timken brand because of its good reputation.