Clunk when slowing down

[HereinDaRockies]

It’s been the outer shell from my steering damper on my car two years ago. It became loose and gave me a similar sound which could only be heard at relatively low speed.

No we are talking about the clunk that occurs down shifting from 3 to 2

 

[Zimm]

Its the programming. You can't replicate it in manual mode. I think varies per unit depending on the backlash present in the drivetrain.

 

[HereinDaRockies]

Now I'm getting this clunk at times, while stopped at a red light, 1.5-2sec after full stop, I may get this audible dull clunk. It seems like it could be the torque converter decoupling/release, after stand still.. Thoughts?

 

[DenisM]

Could be a sticky valve in the mechatronic unit. I'd suggest doing a quick AI search on the ZF8HP55(?) transmission for clues. There's a huge library of info on the net on these transmissions

 

[Commodore]

Now I'm getting this clunk at times, while stopped at a red light, 1.5-2sec after full stop, I may get this audible dull clunk. It seems like it could be the torque converter decoupling/release, after stand still.. Thoughts?

I have been getting the exact same thing. Not every time but often. It’s been happening for a while now.

 

[HereinDaRockies]

I have been getting the exact same thing. Not every time but often. It’s been happening for a while now.

I think mine has only started to do this around 500 miles or so ago.. I am at 8500 on the odo right now

 

[DenisM]

I asked "Perplexity" a few mins ago: Told it about the clunk 1-2 seconds after stopping. IG/ZF8HP55 etc
The answer was as follows:


A clunk that happens 1–2 seconds after a complete stop on a near-new Grenadier is often consistent with drivetrain torque release or a low-speed downshift/lockup event, rather than immediate transmission failure. Because the vehicle is only at 8,000 miles, I would treat this as something to inspect under warranty, especially if the sound is new, getting worse, or paired with any jerk or hesitation.

What it most likely is​

• The 8-speed can be finishing a gear change or releasing clutch load just after the vehicle stops, which can feel like a single clunk.
• Driveline backlash can also show up right as the vehicle settles at idle, especially if the powertrain unloads after braking.
• Mounts, prop shaft joints, differential backlash, or transfer case behavior can all make the same symptom louder.

Why the timing matters​

The fact that it happens 1–2 seconds after stopping makes it less like a simple “bump when coming to rest” and more like a delayed engagement or release event. That delay can point to the transmission control strategy, a converter/clutch action, or a driveline component unloading after the car is fully stationary.

What to observe​

• Does it happen only when hot, only when cold, or both?
• Is it worse in Drive with the brake held than in Neutral or Park?
• Do you feel the clunk through the seat/floor, or only hear it?
• Does it also happen when moving off gently from a stop?

Best next step​

Have the dealer check for software updates, scan for transmission faults, and inspect mounts and driveline play while the vehicle is still under warranty. If the Grenadier is otherwise shifting normally, this is more likely to be a calibration or lash issue than an internal gearbox defect.

A useful test is to note whether the clunk changes if you come to a stop very gently versus more abruptly; that often helps separate a normal drivetrain unload from a mechanical issue.

 

[C-Mack]

Has IA issued any Technical Service Bulletins on the 3 to 2 downshift clunk when slowing to a stop? Any confirmed software upgrades to soften the shifts or modify the transmissions behavior to solve the issue? It really on occurs when the driveline is hot perhaps suggesting greater tolerance stack through component expansion especially in stop and go traffic.

It’s not a very loud or harsh clunk/chunking noise but you can definitely feel it. Avoiding rapid transitions from throttle to brake and slowing down smoothly you can somewhat mask it traffic permitting but it’s always there to one degree or another.

 

[Commodore]

I asked "Perplexity" a few mins ago: Told it about the clunk 1-2 seconds after stopping. IG/ZF8HP55 etc
The answer was as follows:


A clunk that happens 1–2 seconds after a complete stop on a near-new Grenadier is often consistent with drivetrain torque release or a low-speed downshift/lockup event, rather than immediate transmission failure. Because the vehicle is only at 8,000 miles, I would treat this as something to inspect under warranty, especially if the sound is new, getting worse, or paired with any jerk or hesitation.

What it most likely is​

• The 8-speed can be finishing a gear change or releasing clutch load just after the vehicle stops, which can feel like a single clunk.
• Driveline backlash can also show up right as the vehicle settles at idle, especially if the powertrain unloads after braking.
• Mounts, prop shaft joints, differential backlash, or transfer case behavior can all make the same symptom louder.

Why the timing matters​

The fact that it happens 1–2 seconds after stopping makes it less like a simple “bump when coming to rest” and more like a delayed engagement or release event. That delay can point to the transmission control strategy, a converter/clutch action, or a driveline component unloading after the car is fully stationary.

What to observe​

• Does it happen only when hot, only when cold, or both?
• Is it worse in Drive with the brake held than in Neutral or Park?
• Do you feel the clunk through the seat/floor, or only hear it?
• Does it also happen when moving off gently from a stop?

Best next step​

Have the dealer check for software updates, scan for transmission faults, and inspect mounts and driveline play while the vehicle is still under warranty. If the Grenadier is otherwise shifting normally, this is more likely to be a calibration or lash issue than an internal gearbox defect.

A useful test is to note whether the clunk changes if you come to a stop very gently versus more abruptly; that often helps separate a normal drivetrain unload from a mechanical issue.

It feels like a clutch pack releasing. You can actually feel it through the brakes as it takes less brake pedal pressure to hold the car at a stop.

 

[derek_zoolander]

Just commenting my .02 but I had this issue where I had a clunk on slowing from 3/2 usually on a hill. Not all the time but def not rare either. Seems to have magically resolved itself after the first 3500-4k miles.

Not sure why so ymmv but thought I read somewhere that the transmission basically is learning driving style, etc and that could cause some harsh shifts early in its life. Regardless glad my truck no longer does it any more.