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2025 Cummins ZF Transmission Issue?

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scdo

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I towed my ~11k pound trailer today and realized there’s a sound when shifting from first to second gear at high RPMs. The best description I’d give is that it sounds like a slipping / rubbing sound. I tried to record it but it was hard to capture the audio. It only happens from 1st to 2nd under moderate to aggressive acceleration. I can’t reproduce it when not towing (even using tow/haul to force it into 1st).

Any idea what this is?

ChatGPT gave me a few possibilities and this sounds most fitting…


Torque Converter or Clutch Pack Slippage
  • The ZF 8-speed uses internal clutch packs, not traditional bands. If there’s slipping during the 1-2 shift, it could be a sign of:
    • Low or aerated transmission fluid
    • Improper clutch fill timing (a tuning issue)
    • Early wear or contamination in the clutch pack
    • Torque converter not locking or unlocking properly under load
 
scdo said:
I towed my ~11k pound trailer today and realized there’s a sound when shifting from first to second gear at high RPMs. The best description I’d give is that it sounds like a slipping / rubbing sound. I tried to record it but it was hard to capture the audio. It only happens from 1st to 2nd under moderate to aggressive acceleration. I can’t reproduce it when not towing (even using tow/haul to force it into 1st).

Any idea what this is?

ChatGPT gave me a few possibilities and this sounds most fitting…


Torque Converter or Clutch Pack Slippage
  • The ZF 8-speed uses internal clutch packs, not traditional bands. If there’s slipping during the 1-2 shift, it could be a sign of:
    • Low or aerated transmission fluid
    • Improper clutch fill timing (a tuning issue)
    • Early wear or contamination in the clutch pack
    • Torque converter not locking or unlocking properly under load
Click to expand...

How many times has this happened? Can you reproduce it WITH the trailer on, easily? If so, check the color of the fluid to make sure it isn't burnt. If you can reproduce the noise, then take it in to the dealership,, to let the service manager and a mechanic hear it. Just my 2¢.
 
I can reproduce it when towing, yes. It just logistically challenging to get the trailer to the dealer but I will prob need to.
 
scdo said:
I can reproduce it when towing, yes. It just logistically challenging to get the trailer to the dealer but I will prob need to.
Click to expand...

Is that exact tranny used in anything else? If so, are they having the same issues?
 
Did you get an answer to this??? Mine is doing the exact same thing.
 
No, I haven’t. I’m not 100% sure if it’s coming from the tranny vs sound at the hitch or something. Maybe that’s hopeful thinking. Yours is just as I described?

I tried to capture the sound on my phone but it doesn’t come through at all.
 
scdo said:
No, I haven’t. I’m not 100% sure if it’s coming from the tranny vs sound at the hitch or something. Maybe that’s hopeful thinking. Yours is just as I described?

I tried to capture the sound on my phone but it doesn’t come through at all.
Click to expand...
The sound you described is EXACTLY what I hear. Pulling sorta heavy, at 2.5k rpm as it’s shifting.

I do NOT think it’s the hitch, doesn’t really make sense for it to be. To me it sounds like the torque converter is locked while trying to shift, or it’s slipping.

I have free oil changes at the dealer and when I go in I’ll talk to the service manager and explain it. I also can’t bring a loaded trailer to the dealer (maybe I can during the winter but **** I need that truck)

I will likely let it nuke and have them install a new one when it does under warranty.

Please please let me know if you speak with the dealer and what they say
 
Ok, I’m going to plan to discuss it with them when I go in, likely in the next month. There might be a software update for the tranny. I’ll report back here… please do the same!

I will say I can avoid it by being gentle on the throttle until in 2nd.
 
scdo said:
Ok, I’m going to plan to discuss it with them when I go in, likely in the next month. There might be a software update for the tranny. I’ll report back here… please do the same!

I will say I can avoid it by being gentle on the throttle until in 2nd.
Click to expand...
Absolutely
 
scdo said:
Ok, I’m going to plan to discuss it with them when I go in, likely in the next month. There might be a software update for the tranny. I’ll report back here… please do the same!

I will say I can avoid it by being gentle on the throttle until in 2nd.
Click to expand...
There is a new tsb released from ram. Found it on the ram 6th gen fb page. I think mine is 1st to 2nd but might be the same issue
 

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TBxPsi said:
There is a new tsb released from ram. Found it on the ram 6th gen fb page. I think mine is 1st to 2nd but might be the same issue
Click to expand...
Honestly I don’t think this covers it. Mines def 1st to 2nd… only at higher rpm under load.
 
AH64ID said:
6th gen?!

There isn’t even a 5th gen HD yet.
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6th gen is slang used to identify 2025 powertrain, that way every post saying transmissions issues for example, doesn’t need to be specified it’s not the 68RFE
 
TBxPsi said:
6th gen is slang used to identify 2025 powertrain, that way every post saying transmissions issues for example, doesn’t need to be specified it’s not the 68RFE
Click to expand...

It’s not slang, it’s just plain inaccurate. What’s going to happen when a true 6th gen HD gets made?

There were 3 transmission offerings from 13-18 in the HD and no one ever added generations to those. People were smart enough to either mention their transmission or ask.

Keep using it if you want, but there isn’t a lot of credibility to someone who calls a 4th gen truck a 6th gen.
 
AH64ID said:
It’s not slang, it’s just plain inaccurate. What’s going to happen when a true 6th gen HD gets made?

There were 3 transmission offerings from 13-18 in the HD and no one ever added generations to those. People were smart enough to either mention their transmission or ask.

Keep using it if you want, but there isn’t a lot of credibility to someone who calls a 4th gen truck a 6th gen.
Click to expand...
lol k
 
AH64ID said:
It’s not slang, it’s just plain inaccurate. What’s going to happen when a true 6th gen HD gets made?

There were 3 transmission offerings from 13-18 in the HD and no one ever added generations to those. People were smart enough to either mention their transmission or ask.

Keep using it if you want, but there isn’t a lot of credibility to someone who calls a 4th gen truck a 6th gen.
Click to expand...
We own a 2014 Ram 2500 with a G56 and a 2016 Ram 2500 with a 66RFE. Our 2024 Ram 3500 has an Aisin (AS69RC) transmission which was an option back in 13-18. That makes "3", but wasn't there even one more transmission available?
 
Bull Creek said:
We own a 2014 Ram 2500 with a G56 and a 2016 Ram 2500 with a 66RFE. Our 2024 Ram 3500 has an Aisin (AS69RC) transmission which was an option back in 13-18. That makes "3", but wasn't there even one more transmission available?
Click to expand...

Just 3 for the diesel. 68RFE, AS69RC, and G56.

Only the hemi got the 66RFE.
 
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