1st Gear Coasting Clunk

[kubota31]

I know there are 10,000 threads associated with 'transmission clunk' - but can't find any one with the problem I have. Wondering if anyone else has had something similar / I might be able to guide the dealer for a fix...

2023 Tremor - transmission clunks (noise/truck shakes) if: you’re at a full stop and let off the brakes, while coasting downhill (i.e. coasting with acceleration without pressing the gas pedal). Occurs at exactly 3MPH every time - no deviation, with the truck remaining in first gear after the clunk. It does not shift from first - just clunks and continues to pick up speed in first gear whilst coasting, eventually shifting into 3rd as you'd expect.

You can feel it build up - almost like tension as the truck stays at 3MPH momentarily before the clunk and acceleration continues afterwards.

There is no clunk:

• If the truck is coasting downhill at a steeper grade where it can shift into 3rd quickly(same obviously if you were on the gas accelerating at any grade).
• If you are already rolling - even at 1MPH - and let it coast/accelerates to 3MPH, no clunk, and will continue to accelerate until shift, etc.. must be at a complete stop to replicate.
• If you place the truck in manual shift mode and hold in 1st gear.

Have been to the dealer(s) for this multiple times, as it occurs in perpetuity over and over again when, for example, you’re in stop and go traffic on the highway - which I can sit in up to an hour a day… so fun / not a tolerable condition.

• Had shift tables reset
• Had valve body replaced
• Most recently had a new transmission software flash installed

This has been occurring, along with rough downshifts, from before the first 1,000 miles on the truck, so nothing new unfortunately.

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[HammaMan]

TC locking up where the hill allows slight vehicle acceleration during the transition, slacking the driveline (backlash) which is then taken back up as the TC locks as engine has a higher rev than the TC's output shaft. Basically driveline unloads ever so slightly and then slam reloads when the TC locks. When I'm cruising and doing slight rolling hills there's a few particular ones where conditions align where potential energy slightly unloads the driveline as it begins to back off but speed drops to bring back in power and it can go from unloaded to loaded within ~1.5 seconds (maybe quicker) or so and it's noticeable around 60mph under very specific circumstances (felt it at other speeds when the hills cause an unload -- it's rare but I understand what it is. It's neither hill nor speed specific, it's the right speed on the right hill conditions -- even headwinds and tailwinds are a variable so duplicating it is very difficult, fortunately in the PB I have the hybrid gauges that let's me see what the driveline is doing which made understanding it much easier).

Unloading (coasting) or initial acceleration only ever let you feel one or the other, but when you feel an unload/load and truck can't anticipate it you will feel it especially when the TC is normally expecting the driveline to be loaded and naturally slip a little bit -- with it unloaded it makes it a fast engagement. While ever so slightly rolling forward put it into reverse and see if you can notice the driveline backlash. Try slow roll forward into reverse and slow roll backwards into drive and see if you can get a version of this to occur. Now it won't bang like a TC lockup as with an unloaded driveline it can really hit, but if it were normal acceleration there's not a chance for the driveline to unload. Normally F to R is really soft but a TC lockup if the truck believes its accelerating will slam. It's just oddities when the right alignment of circumstances occur.

 

[SilverPigeon]

This is interesting, because I am under the impression (I can't remember where I saw it) that the 10R80 TC locks up in all forward gears except 1st.

If this is only happening in 1st, I would firstly use FORScan (or FDRS?) to look at any DTCs and investigate them if any. If there are no trouble codes, I would stop use of adaptive learning to see how the "dumbed-down" transmission behaves. If it's still evidenced, without DTCs, I would see if there are any service procedures (tests) that might shed light on the issue. Failing all that, try another shop for a second and even third opinion before potentially costly invasive diagnosis and repair.

 

[HammaMan]

TCC is torque converter clutch

 

[SilverPigeon]

Thanks @HammaMan, good to know ?. I think doing a little further investigating couldn't hurt the OP though, especially if it's of concern to them.

Incidentally, the only "clunk" I can replicate out of my 10R80 is when I am coming up to a stop sign and brake moderately heavily from around 30mph; then I can get a clunk as it shifts down to 1st. This only happens when the fluid is cold so I consider it normal and expected. ?‍

 

[Oxford_Powerboost]

This is interesting, because I am under the impression (I can't remember where I saw it) that the 10R80 TC locks up in all forward gears except 1st.

If this is only happening in 1st, I would firstly use FORScan (or FDRS?) to look at any DTCs and investigate them if any. If there are no trouble codes, I would stop use of adaptive learning to see how the "dumbed-down" transmission behaves. If it's still evidenced, without DTCs, I would see if there are any service procedures (tests) that might shed light on the issue. Failing all that, try another shop for a second and even third opinion before potentially costly invasive diagnosis and repair.

I’m not entirely sure what’s going on. But if you put it in M1 in the exact same scenario - that exact point where the clunk is felt will be where your speed is held. It’s like the trans is in some kind of pseudo neutral state after 3mph to let you roll and if you lock it in M1, it won’t do that, holding your speed back and actually raiding rpm

 

[Ford Motor Company]

I know there are 10,000 threads associated with 'transmission clunk' - but can't find any one with the problem I have. Wondering if anyone else has had something similar / I might be able to guide the dealer for a fix...

2023 Tremor - transmission clunks (noise/truck shakes) if: you’re at a full stop and let off the brakes, while coasting downhill (i.e. coasting with acceleration without pressing the gas pedal). Occurs at exactly 3MPH every time - no deviation, with the truck remaining in first gear after the clunk. It does not shift from first - just clunks and continues to pick up speed in first gear whilst coasting, eventually shifting into 3rd as you'd expect.

You can feel it build up - almost like tension as the truck stays at 3MPH momentarily before the clunk and acceleration continues afterwards.

There is no clunk:

• If the truck is coasting downhill at a steeper grade where it can shift into 3rd quickly(same obviously if you were on the gas accelerating at any grade).
• If you are already rolling - even at 1MPH - and let it coast/accelerates to 3MPH, no clunk, and will continue to accelerate until shift, etc.. must be at a complete stop to replicate.
• If you place the truck in manual shift mode and hold in 1st gear.

Have been to the dealer(s) for this multiple times, as it occurs in perpetuity over and over again when, for example, you’re in stop and go traffic on the highway - which I can sit in up to an hour a day… so fun / not a tolerable condition.

• Had shift tables reset
• Had valve body replaced
• Most recently had a new transmission software flash installed

This has been occurring, along with rough downshifts, from before the first 1,000 miles on the truck, so nothing new unfortunately.

Hi there! Would you send us a private message with your VIN and dealership name and location? I’d like to look into this concern on my end.  

 

[kubota31]

TC locking up where the hill allows slight vehicle acceleration during the transition, slacking the driveline (backlash) which is then taken back up as the TC locks as engine has a higher rev than the TC's output shaft. Basically driveline unloads ever so slightly and then slam reloads when the TC locks. When I'm cruising and doing slight rolling hills there's a few particular ones where conditions align where potential energy slightly unloads the driveline as it begins to back off but speed drops to bring back in power and it can go from unloaded to loaded within ~1.5 seconds (maybe quicker) or so and it's noticeable around 60mph under very specific circumstances (felt it at other speeds when the hills cause an unload -- it's rare but I understand what it is. It's neither hill nor speed specific, it's the right speed on the right hill conditions -- even headwinds and tailwinds are a variable so duplicating it is very difficult, fortunately in the PB I have the hybrid gauges that let's me see what the driveline is doing which made understanding it much easier).

Unloading (coasting) or initial acceleration only ever let you feel one or the other, but when you feel an unload/load and truck can't anticipate it you will feel it especially when the TC is normally expecting the driveline to be loaded and naturally slip a little bit -- with it unloaded it makes it a fast engagement. While ever so slightly rolling forward put it into reverse and see if you can notice the driveline backlash. Try slow roll forward into reverse and slow roll backwards into drive and see if you can get a version of this to occur. Now it won't bang like a TC lockup as with an unloaded driveline it can really hit, but if it were normal acceleration there's not a chance for the driveline to unload. Normally F to R is really soft but a TC lockup if the truck believes its accelerating will slam. It's just oddities when the right alignment of circumstances occur.

Interesting. I'll try that. This is something that happens exactly at 3mph. And it's fairly easy to replicate if you just go onto a modest slope facing downhill and let off the gas. The "reflash" of the transmission did somewhat work, where there were times it didn't slam. Then it just kinda fell back into slamming non-stop.

I’m not entirely sure what’s going on. But if you put it in M1 in the exact same scenario - that exact point where the clunk is felt will be where your speed is held. It’s like the trans is in some kind of pseudo neutral state after 3mph to let you roll and if you lock it in M1, it won’t do that, holding your speed back and actually raiding rpm

Yeah so that's the thing M1 - zero clunk (or lock, if that's what it is). I guess that was my control for testing this

 

[kubota31]

TC locking up where the hill allows slight vehicle acceleration during the transition, slacking the driveline (backlash) which is then taken back up as the TC locks as engine has a higher rev than the TC's output shaft. Basically driveline unloads ever so slightly and then slam reloads when the TC locks. When I'm cruising and doing slight rolling hills there's a few particular ones where conditions align where potential energy slightly unloads the driveline as it begins to back off but speed drops to bring back in power and it can go from unloaded to loaded within ~1.5 seconds (maybe quicker) or so and it's noticeable around 60mph under very specific circumstances (felt it at other speeds when the hills cause an unload -- it's rare but I understand what it is. It's neither hill nor speed specific, it's the right speed on the right hill conditions -- even headwinds and tailwinds are a variable so duplicating it is very difficult, fortunately in the PB I have the hybrid gauges that let's me see what the driveline is doing which made understanding it much easier).

Unloading (coasting) or initial acceleration only ever let you feel one or the other, but when you feel an unload/load and truck can't anticipate it you will feel it especially when the TC is normally expecting the driveline to be loaded and naturally slip a little bit -- with it unloaded it makes it a fast engagement. While ever so slightly rolling forward put it into reverse and see if you can notice the driveline backlash. Try slow roll forward into reverse and slow roll backwards into drive and see if you can get a version of this to occur. Now it won't bang like a TC lockup as with an unloaded driveline it can really hit, but if it were normal acceleration there's not a chance for the driveline to unload. Normally F to R is really soft but a TC lockup if the truck believes its accelerating will slam. It's just oddities when the right alignment of circumstances occur.

I had some time to try rolling forward / backward at a slow speed and shifting into the opposite direction (reverse / forward, respectively). No noticeable response from the transmission - shifts smoothly / no noise.

 

[ChaoticCarpenter]

Not sure if anyone found out the truth here, I have the same issue and Ford just told me the same thing as what you’re describing. Driveline slack. I’m not a mechanic but it sounds like BS to me. My previous truck didn’t do this.

 

[Jerome10]

I’m not sure I have this exact scenario but similar.

wanted to see if any update perhaps?

I’ll try to pay more attention to speed and all that but for me it’s just coasting to a red light, I’d guess maybe 50% of the time the truck kinda just thuds into 1st.

Other times it is completely smooth and unnoticeable.

It’s never bad or harsh. You just feel the thud as it drops into 1st.

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