Clunk when slowing down

[Zimm]

This is good ammunition as I believe it is t-case preload. We’ll have to focus on this one issue until resolved.

It only does it on 3-2 and not all the time. It never does it anywhere else. I'm not grasping how it can be the t-case preload. On a really bad shift, I can feel it when 3rd is released as it gives the illusion of acceleration because its no longer decelerating, and I can fell the second grab. You'll have to explain your assessment that to me. I think its the programming.

 

[Dopplemax]

Knock on wood, I haven't had this issue...yet. The wife's 2023 Escalade V had what sounds like a similar condition that the dealer(s) kept telling us was normal. Finally got one of them to take it apart and they found the clutch plates in the TC were slipping. Replaced the plate shims with a different thickness and it went away completely. So we traded it in lol on a 2025 non-V that doesn't have the full time AWD nor 685 HP. So far so good.

 

[BrianK]

Any updates on this issue or additional repair and warranty experience? I am still having the clunking problem from 3-2, but also when coming on and off throttle at times, low speeds, 2nd gear typically. The severity has lessened. It seems almost like slop in the driveline. I suspect the T-Case based on previous comments. It’s a: throttle on, fraction of a second, then clunk; throttle off, fraction of a second, then clunk.

 

[NQ94]

Any updates on this issue or additional repair and warranty experience? I am still having the clunking problem from 3-2, but also when coming on and off throttle at times, low speeds, 2nd gear typically. The severity has lessened. It seems almost like slop in the driveline. I suspect the T-Case based on previous comments. It’s a: throttle on, fraction of a second, then clunk; throttle off, fraction of a second, then clunk.

The performance ZF transmission groups and transmission tech groups have mentioned 3-2 down shift and a 6-7 upshift noise and poor quality shifts in some 8HP transmissions in other car brands. Some of the repairs suggested were for the dealer reset the trans back to default settings and let it readapt/relearn, servicing and checking the pan and removing valve bodies for inspection and checking the separator plates. ZF does not seem to suffer the separator plate and valve body issues the GM 10 speed has but it does have its own faults.
The best bet would be taking the car to a transmission shop that specialises in ZF transmissions for a second opinion, they're more likely to have the tools and experience to test the transmission properly.

 

[AWo]

It seems to be about the adaptation values. These are self-learned values by the gearbox ECU to optimize the shifting. They adjust to wear and tolerances over time.
They are responsible for the clutch pressures generated by valves of the various clutches in the gearbox, the speed to pre-load a clutch, the shifting itself and the holding pressure.

If the gearbox is new, a reset leads to re-learning. So shifting should become better over time. If the gearbox is in use for quite a time the small filters of the valves can be clogged and the adaptions values become incorrect. This can not be fixed by flushing the gearbox! You have to dismantle these valves and clean them.

Sometimes it is worth to measure the adaption values to get a clear picture of the issues.

AWo

 

[Tom109]

Sometimes it is worth to measure the adaption values to get a clear picture of the issues.

AWo

How is this accomplished?

 

[AWo]

How is this accomplished?

You need the right equipment and the intended values for that, it is a work shop thing.....so go and find a work shop which is specialised in ZF gearboxes or automatic gearboxes...

AWo

 

[Zimm]

The performance ZF transmission groups and transmission tech groups have mentioned 3-2 down shift and a 6-7 upshift noise and poor quality shifts in some 8HP transmissions in other car brands. Some of the repairs suggested were for the dealer reset the trans back to default settings and let it readapt/relearn, servicing and checking the pan and removing valve bodies for inspection and checking the separator plates. ZF does not seem to suffer the separator plate and valve body issues the GM 10 speed has but it does have its own faults.
The best bet would be taking the car to a transmission shop that specialises in ZF transmissions for a second opinion, they're more likely to have the tools and experience to test the transmission properly.

resetting didnt do anything.

 

[Tom109]

@Zimm - is your 3-2 the same? For the most part mine is the same clunk, but speed dependent it is quieter or even absent. I need to log the speed/clunk differences - it still really bothers me. I’m going to open a case direct with IA.

 

[NQ94]

It seems to be about the adaptation values. These are self-learned values by the gearbox ECU to optimize the shifting. They adjust to wear and tolerances over time.
They are responsible for the clutch pressures generated by pistons of the various clutches in the gearbox, the speed to pre-load a clutch, the shifting itself and the holding pressure.

If the gearbox is new, a reset leads to re-learning. So shifting should become better over time. If the gearbox is in use for quite a time the small filters of the hydraulic pistons can be clogged and the adaptions values become incorrect. This can not be fixed by flushing the gearbox! You have to dismantle these pistons and clean them.

Sometimes it is worth to measure the adaption values to get a clear picture of the issues.

AWo

Are the small screens that you are referring to for the solenoids (ERPS) on the mechatronics module?

 

[AWo]

Are the small screens that you are referring to for the solenoids (ERPS) on the mechatronics module?
View attachment 7899514

Screens....? I do not understand (the question), can you explain, please?

AWo

 

[Zimm]

@Zimm - is your 3-2 the same? For the most part mine is the same clunk, but speed dependent it is quieter or even absent. I need to log the speed/clunk differences - it still really bothers me. I’m going to open a case direct with IA.

It changes depending on the circumstances. its NOT the tcase. I cannot replicate it in 3-4 and above.

I can actually make it "clunk" slowly. In an empty lot, I get the car into third, and let it drift down. It holds gear almost like a stick in third, then I can feel it release third, and since its not slowing as much because it's actually hanging in neutral for 1/2 second, it gives the sensation of speeding up, and then it suddenly grabs second. Now, if I time that right, I can touch the throttle and it will clunk. Basically, there's a weird delay in the shift.

I'm having a hard time telling if its the "A" clutch that engages for 1 and 2, or the tq converter not having enough slip, or a sticky solenoid, or maybe a combo of issues that is exacerbated due to the excessive way they have the transmission set up to hold gear and slow the truck, because when I come to a stop, there are times the car vibrates until I feel a pop as it releases first. It's fucked up.

 

[AWo]

Are the small screens that you are referring to for the solenoids (ERPS) on the mechatronics module?
View attachment 7899514

Ahh, now I see. Yes, that is what I meant, but I used the wrong term. I wrote piston (corrected already) but I meant valve.

AWo