Launch Shudder when towing

[DGamelin]

Launch shutter is not just a driveshaft angle thing. It can be caused by a clutch in the manual or problems in your automatic. My 04.5 had an issue when I first got it, I aligned the shaft and the problem went away. Later I installed an aftermarket towing clutch. When I was loaded down south and things got heat soaked the shutter was so bad I thought it would throw the driveshaft at any time. The shutter only lasted as long as you were letting the clutch out. Once the clutch was all of the way engaged the shutter was gone. I can see an automatic having the same type of issue of the converter locking and unlocking or the clutch plates not completely engaging because of low line pressure or software issue for the automatic. Sounds to me like you have a transmission issue of some type. I've never seen a driveline shutter all the way from the bottom up to 40mph. You said when it hits 4th gear it goes away, I'd have to believe it's in the trans. I have a 2015 on order. It should be here this week. It's a 3500 dully with the Aisin and air ride. When I was first looking at this I thought because of the way the leaf spring has been reconfigured I expected some type of launch shutter due to excessive axle wrap with big loads. I figured I'd end up putting a set of radius rods from the bottom of the axle to further up the frame. I'm dissapointed to hear these issues. I miss my old truck, all of the bugs were finally gone, now I get to do it again.

 

[Cummins12V98]

I can tell you the little I have towed with my rear air ride dually I can tell you it gets a 20K load moving easily! Now with 3:42's shudder can happen.

 

[HorseMan-AR]

Towed the fiver this weekend. Coming out of the park, there are several fairly steep grades. Tried tow haul and tried no tow haul. Made no difference. Still experienced the shudder when the AISIN would shift into 3rd. I manually shift to 2nd, and it goes away. The shift to 3rd brings RPMs down to around 1200-1400 RPMs best I could tell. I think the transmission is causing the shudder, because it's shifting into 3rd too quickly. I'm just not sure. Almost like its lugging too much.

 

[Newsa]

Sounds like you are driving it like it's supposed to be driven. Downshift when you feel shudder coming on. That's what I do with my G56.

Since both Cummins and Aisin are bullet-proof. They will withstand all the shudder you can throw at them

 

[transe]

Towed the fiver this weekend. Coming out of the park, there are several fairly steep grades. Tried tow haul and tried no tow haul. Made no difference. Still experienced the shudder when the AISIN would shift into 3rd. I manually shift to 2nd, and it goes away. The shift to 3rd brings RPMs down to around 1200-1400 RPMs best I could tell. I think the transmission is causing the shudder, because it's shifting into 3rd too quickly. I'm just not sure. Almost like its lugging too much.

Since what you're describing is at speed (not right at launch from a stop), I suspect that what you're feeling is engine torsional vibrations. The torque from the engine is not constant - it fluctuates or pulses due to the individual cylinders firing. These fluctuations in torque are called torsional vibrations. The amount of fluctuation increases as engine speed drops, and also increases as overall torque increases. So the worst situation is at low engine speeds, when requesting high torque.

It is possible that these torque pulses are extreme enough to cause the torque converter clutch (TCC) to slip. If that happens, you get a shudder. The TCC is slipping and grabbing, slipping and grabbing, repeatedly. Each torque pulse (that exceeds the TCC capacity) breaks it loose again, then as the torque subsides, the TCC grabs again.

If the vibration you get is primarily something you HEAR, then I suspect it's the engine torsional vibrations. If it's something you FEEL (a shudder) then I'd suspect TCC slippage (due to high engine torsionals). So either way, torsional vibrations are likely the cause. The fix (as it seems you've already figured out) is to back off the throttle (to lower the torque), or downshift the trans (to raise the engine speed). Either one will reduce the level of engine torsionals.

 

[HorseMan-AR]

Thanks amigo! Always a pleasure hearing from you. Very informative, as always!

Since what you're describing is at speed (not right at launch from a stop), I suspect that what you're feeling is engine torsional vibrations. The torque from the engine is not constant - it fluctuates or pulses due to the individual cylinders firing. These fluctuations in torque are called torsional vibrations. The amount of fluctuation increases as engine speed drops, and also increases as overall torque increases. So the worst situation is at low engine speeds, when requesting high torque.

It is possible that these torque pulses are extreme enough to cause the torque converter clutch (TCC) to slip. If that happens, you get a shudder. The TCC is slipping and grabbing, slipping and grabbing, repeatedly. Each torque pulse (that exceeds the TCC capacity) breaks it loose again, then as the torque subsides, the TCC grabs again.

If the vibration you get is primarily something you HEAR, then I suspect it's the engine torsional vibrations. If it's something you FEEL (a shudder) then I'd suspect TCC slippage (due to high engine torsionals). So either way, torsional vibrations are likely the cause. The fix (as it seems you've already figured out) is to back off the throttle (to lower the torque), or downshift the trans (to raise the engine speed). Either one will reduce the level of engine torsionals.

 

[HorseMan-AR]

Transengineer: I continue to experience these torsional vibrations. I assume by your explanation I'll always experience those? Would replacing the TCC help? Is this something I live with? It is frustrating to think I bought a 3500 HD truck with the HD Aisin and have to live with such things, particularly when I'm nowhere near the capacity of the truck. My fiver is only 12k fully loaded, and that is max. Any further comments?

Since what you're describing is at speed (not right at launch from a stop), I suspect that what you're feeling is engine torsional vibrations. The torque from the engine is not constant - it fluctuates or pulses due to the individual cylinders firing. These fluctuations in torque are called torsional vibrations. The amount of fluctuation increases as engine speed drops, and also increases as overall torque increases. So the worst situation is at low engine speeds, when requesting high torque.

It is possible that these torque pulses are extreme enough to cause the torque converter clutch (TCC) to slip. If that happens, you get a shudder. The TCC is slipping and grabbing, slipping and grabbing, repeatedly. Each torque pulse (that exceeds the TCC capacity) breaks it loose again, then as the torque subsides, the TCC grabs again.

If the vibration you get is primarily something you HEAR, then I suspect it's the engine torsional vibrations. If it's something you FEEL (a shudder) then I'd suspect TCC slippage (due to high engine torsionals). So either way, torsional vibrations are likely the cause. The fix (as it seems you've already figured out) is to back off the throttle (to lower the torque), or downshift the trans (to raise the engine speed). Either one will reduce the level of engine torsionals.

 

[Newsa]

Just bumping an older thread, but my new 2015 3500 SRW with OEM rear adjustable air ride is experiencing what I call this launch shudder. It only does it when loaded with fiver (11-12K pounds). Fiver is well within tow/payload capacity of truck. Usually only feel shudder when loaded AND going up an incline - at low speeds. Only does it when upshifting from 2nd to 3rd - almost like truck shifts into 3rd with RPMs being too low. I can manually shift to 2nd and immediately, the shudder disappears. Crew cab with one piece drive shaft, AISIN, 4x4, 3.42 rear axle.

I have all the latest transmission flashes and truck as 3400 miles on her. Any comments?

When you say RPM'S being low, what does the tach say before and after shifting from 2nd to 3rd?

I find it hard to believe the TCC is behaving that way at 1/2 towing capacity.

 

[transe]

Transengineer: I continue to experience these torsional vibrations. I assume by your explanation I'll always experience those? Would replacing the TCC help? Is this something I live with? It is frustrating to think I bought a 3500 HD truck with the HD Aisin and have to live with such things, particularly when I'm nowhere near the capacity of the truck. My fiver is only 12k fully loaded, and that is max. Any further comments?

Some torsionals are indeed normal (when operating at low engine speed with high torque). But if you are getting TCC shudder ("rumble strip" vibrations), then you may indeed need a new converter (assuming you are running stock programming). Demo it for the dealer; sounds like maybe your TCC capacity is too low. In the meantime, shift it manually when towing at heavy throttle, so you can delay the 2-3 upshift and avoid the shudder.

I think you did say you were using Tow/Haul mode, correct? That should help.

 

[HorseMan-AR]

Thanks again. Yes, it's the "rumble strip" vibration. All stock here. The only time I get it is when towing and going up hill...generally a steep hill. I may have to sweet talk dealer on the TCC...my luck at demonstrating it to dealer isn't good, and I'd have to hook up fiver and find an incline.
It is very frustrating, however.

Edit: I've tried tow/haul, and none tow/haul. It happens when transmission shifts into 3rd...the RPMs are about 1200, maybe 1100...best I can tell from RPM gauge. Right in that area is when I get the mighty rumble strip vibration.

Some torsionals are indeed normal (when operating at low engine speed with high torque). But if you are getting TCC shudder ("rumble strip" vibrations), then you may indeed need a new converter (assuming you are running stock programming). Demo it for the dealer; sounds like maybe your TCC capacity is too low. In the meantime, shift it manually when towing at heavy throttle, so you can delay the 2-3 upshift and avoid the shudder.

I think you did say you were using Tow/Haul mode, correct? That should help.

 

[HorseMan-AR]

Hard for me to believe as well. The vibration starts in 3rd about 1100-1200 RPMs (basically as soon as the shift from 2 to 3 occurs). I shift manually back down to 2nd and RPMs bump up (not sure how high, not drastic, because I'm never really gunning it) and vibration goes away. Hope that makes sense.

When you say RPM'S being low, what does the tach say before and after shifting from 2nd to 3rd?

I find it hard to believe the TCC is behaving that way at 1/2 towing capacity.

 

[Newsa]

Hard for me to believe as well. The vibration starts in 3rd about 1100-1200 RPMs (basically as soon as the shift from 2 to 3 occurs). I shift manually back down to 2nd and RPMs bump up (not sure how high, not drastic, because I'm never really gunning it) and vibration goes away. Hope that makes sense.

Replacing the TCC won't fix engine lugging. That's all that can happen under load at1100 1100-1200 RPM's

From cumminsforum:

So I now have 18000km on my truck. I have been towing heavy and towing often and for the most part I'm really pleased with it. I do notice a few big differences (some good some not) from my older truck which had the 68RFE. Note: My towing involves loads around 20000lbs. I wonder if anyone else notices some of the following: The Aisin is much better at finding the right gear by itself than the 68RFE, but do you notice how it's sometimes almost too sensitive to throttle input? Sometimes it's almost like it's hunting between 4-5 and 5-6. I find myself using the button shifter alot. Sometimes in 3rd, the torque converter clutch will stay locked until the truck falls below it's peak torque resulting in lugging. I'm getting better at avoiding this by anticipating how the truck shifts at medium speeds on steep hills.

 

[HorseMan-AR]

I suppose I've found the throttle sensitive, and I agree about lugging. However, for my light weight fiver and what the truck is built to tow, I don't feel like I should have to tell this 65k truck how to shift in order to avoid lugging. Just my opinion.

I'm not anywhere close to capacity with my fiver. GVWR on my fiver is 11,800. I'm probably close to that, as the wife loads everything but the kitchen sink! But, considering what the truck can handle, I think it reasonable to believe this ole' Aisin and HO engine can sort out when to shift.

 

[Newsa]

I understand your frustration. My wife would be asking me why I didn't buy a duramax/allison.

If I shifted my G56 like that, she'd be trading me in, too. She would be screaming!

I have an opinion that many here will not like. Someone posted on another thread that talking to Ram engineers at an Expo, they learned that Aisin doesn't share info about their HD trannies. And Aisin does their own comtrol programming that is not communicating with the engine.

I guess the Aisin gets its engine RPMs from the input shaft? Not from the ECM?

My opinion is that Ram should not have outsourced that transmission to Aisin....... Since the Aisin company isn't allowing Ram to fully integrate the control of it with the Cummins.

 

[Newsa]

If the Aisin was able to get throttle position/fuel consumption/injection timing, info along with RPM info, it should know that it needs to shift at a higher RPM.

It sounds like it's acting like you are always on level ground. It's not getting all the data it needs to know to shift at higher RPM.

 

[transe]

Are you sure about your engine speed? I just checked the shift schedule for the Aisin, and the lowest engine speed you should see after a 2-3 upshift (unless you're at very light / closed throttle) is about 1365 RPM.

 

[HorseMan-AR]

Are you sure about your engine speed? I just checked the shift schedule for the Aisin, and the lowest engine speed you should see after a 2-3 upshift (unless you're at very light / closed throttle) is about 1365 RPM.

Well, I have the Longhorn dash, and if memory serves, I've got a RPM gauge that has 3 or 4 marks between 1000 and 2000...when the vibration starts, it's always above the 1000 RPM mark, and covers the second little mark (I think) - I'm guessing that's about 1200 - but there is no way to tell if it's really 1200 or 1300, you know. It could be 1365 or so...hard to tell really. Maybe I need to put more foot in the throttle! I've tried that actually, and you've really got to put your foot into it to get the shift down to 2, so I always manually shift. It always seems like the Aisin is trying to guess whether it should be in 2 or 3...like there's a little glitch there somewhere. Never happens when not loaded tho.

On edit: I tried to get the wife to video the shudder this weekend, but you just can't hear it on my phone over the road noise and regular engine sound. I really appreciate your help, TransEngineer - it's helpful to have this discussion. Maybe I'm doing something wrong, I don't know.

 

[transe]

I think if I were you, I would simply hold it in 2nd gear (manual mode "2") when towing up a steep grade, until you reach about 2400 engine RPM, then tap it up to "3" (and back to "D"). At that point, the engine speed should be ~1600 RPM after the 2-3 upshift, which will hopefully avoid the shudder.

 

[HorseMan-AR]

Thanks again. I'll give it a try.

I think if I were you, I would simply hold it in 2nd gear (manual mode "2") when towing up a steep grade, until you reach about 2400 engine RPM, then tap it up to "3" (and back to "D"). At that point, the engine speed should be ~1600 RPM after the 2-3 upshift, which will hopefully avoid the shudder.

 

[Newsa]

Someone mentioned before that these trannies adapt to driving style. I hate to see our friend Horseman manually shifting his Aisin that he paid $4000 for.

One question: If he continues to just let the Aisin lug his Cummins, will it eventually learn a new shift point?

or is it just the 68 RFE that adapts to driver's driving style?