Launch Shudder when towing

[transe]

The shift adaptations adjust the shift QUALITY, not the shift POINTS. So the actual shift pattern will not change over time.

The only real "fix" would likely be a replacement converter (since apparently the existing converter's TCC capacity is too low to handle the peak engine torsionals).

 

[Newsa]

Why would the TCC not handle torque in 3rd, but operate fine in 4th & 5th where there is more resistance torque? ( And the engine still has it's torque bursts.

Isn't the same TCC used in all gears?

Is there more torque management in the higher gears? In my G56, there is torque management mostly at low speeds.

 

[transe]

Why would the TCC not handle torque in 3rd, but operate fine in 4th & 5th where there is more resistance torque? ( And the engine still has it's torque bursts.

Isn't the same TCC used in all gears?

Is there more torque management in the higher gears? In my G56, there is torque management mostly at low speeds.

The problem is not the "base" engine torque. The problem is torsionals. The actual engine torque is not constant; it fluctuates as the individual cylinders fire. So if the nominal engine torque is (for example) 500 ft-lbs, it may actually be varying (rapidly) between maybe 470 - 530 ft-lbs. That variation is called torsional vibrations (or simply, torsionals).

The level of torsionals changes with load and engine speed. Torsionals are highest at low engine speed, and maximum torque. So the worst case is heavy throttle (high torque) at low engine speed. Let's say the TCC capacity is 1000 ft-lbs (I'm just pulling numbers out of the air for this example). If the max nominal engine torque is 850 ft-lbs, then maybe with torsionals the actual peak is 950 ft-lbs (still OK for the TCC).

I'm thinking perhaps there is a problem with his TCC. For example, if his TCC capacity were only 930 ft-lbs, it would slip (shudder) if the torsionals pushed the peak torque to 950. Apparently 3rd gear is the worst case because engine speed is lower than in 4th or 5th. That means torsionals will be higher. Using our example, suppose the peak torsionals were +100 ft-lbs at 1365 RPM, but only +70 ft-lbs at 1500 RPM. Then his TCC would shudder in 3rd (at 1365 RPM) but not in other gears (at 1500 RPM).

Now admittedly this is all conjecture on my part. But my point is: Yes, the TCC capacity is the same in all gears. But the level of torsionals (and therefore, the actual engine torque spike peaks) will vary with engine speed, so if engine speed is lower in 3rd, torsionals will be higher, and therefore TCC shudder may exist in 3rd but not in other gears. If he's getting TCC shudder, then either his engine torque spikes are higher than normal, or his TCC capacity is lower than normal. Not low enough to cause problems in most driving, but low enough to give shudder at the point of peak torsionals.

If he holds it in 2nd gear longer, then his engine speed in 3rd will be higher, therefore torsionals will be lower (hopefully low enough to avoid the shudder). So delaying the 2-3 upshift doesn't "fix" the converter, it just reduces the peak torque spikes. Hope that makes sense!

 

[Ram4Sam]

Let me add to the confusion....... I also have a slight case of the shudders but completely different circumstance. Once in awhile, I will get a slight shudder during the 1-2 shift, daily driving city streets. No shudder during the 1-2 shift hot rodding up a freeway onramp. Towing my 10,000 lb 5er, in tow/haul mode, all shifts are fine, no shudder........ Since I have stayed at a Holiday inn before, my two cents worth is that this might be a driveline issue.

Sam

 

[HorseMan-AR]

Thanks, Transengineer - always good reading your posts. I assume replacing my TCC would entail them dropping my brand new Aisin? Yuck! Is it just that my TCC may be a bad one, or is it programming maybe? I'm just wondering why my TCC is not working like everyone else? Something I've done to cause this, you think, or just a bad one? Is it just my driving style? Just trying to understand why my TCC ain't working right (we think)? Aren't the TCCs all made the same? Is the TCC just like any other part that may require a replacement from time-to-time?

How long do you think it would take a tech to do this work, if they have the parts? Are we talking a day job, several days, or weeks?

The problem is not the "base" engine torque. The problem is torsionals. The actual engine torque is not constant; it fluctuates as the individual cylinders fire. So if the nominal engine torque is (for example) 500 ft-lbs, it may actually be varying (rapidly) between maybe 470 - 530 ft-lbs. That variation is called torsional vibrations (or simply, torsionals).

The level of torsionals changes with load and engine speed. Torsionals are highest at low engine speed, and maximum torque. So the worst case is heavy throttle (high torque) at low engine speed. Let's say the TCC capacity is 1000 ft-lbs (I'm just pulling numbers out of the air for this example). If the max nominal engine torque is 850 ft-lbs, then maybe with torsionals the actual peak is 950 ft-lbs (still OK for the TCC).

I'm thinking perhaps there is a problem with his TCC. For example, if his TCC capacity were only 930 ft-lbs, it would slip (shudder) if the torsionals pushed the peak torque to 950. Apparently 3rd gear is the worst case because engine speed is lower than in 4th or 5th. That means torsionals will be higher. Using our example, suppose the peak torsionals were +100 ft-lbs at 1365 RPM, but only +70 ft-lbs at 1500 RPM. Then his TCC would shudder in 3rd (at 1365 RPM) but not in other gears (at 1500 RPM).

Now admittedly this is all conjecture on my part. But my point is: Yes, the TCC capacity is the same in all gears. But the level of torsionals (and therefore, the actual engine torque spike peaks) will vary with engine speed, so if engine speed is lower in 3rd, torsionals will be higher, and therefore TCC shudder may exist in 3rd but not in other gears. If he's getting TCC shudder, then either his engine torque spikes are higher than normal, or his TCC capacity is lower than normal. Not low enough to cause problems in most driving, but low enough to give shudder at the point of peak torsionals.

If he holds it in 2nd gear longer, then his engine speed in 3rd will be higher, therefore torsionals will be lower (hopefully low enough to avoid the shudder). So delaying the 2-3 upshift doesn't "fix" the converter, it just reduces the peak torque spikes. Hope that makes sense!

 

[transe]

I assume replacing my TCC would entail them dropping my brand new Aisin? Yuck! Is it just that my TCC may be a bad one, or is it programming maybe? I'm just wondering why my TCC is not working like everyone else? Something I've done to cause this, you think, or just a bad one? Is it just my driving style? Just trying to understand why my TCC ain't working right (we think)? Aren't the TCCs all made the same? Is the TCC just like any other part that may require a replacement from time-to-time?

How long do you think it would take a tech to do this work, if they have the parts? Are we talking a day job, several days, or weeks?

Yes, the TCC is inside the converter, so to replace the TCC you replace the converter, which requires removing the trans, which should be a one-day (but basically all-day!) job.

All TCCs should be the same, but I'd guess perhaps there is a small tear in one of the seal lips (giving a slight pressure loss, that reduces the capacity) or some other hardware issue that might be causing lower capacity. I would not think it's software-related.

Since apparently the problem only happens when towing up a grade, just after the 2-3 upshift, it would seem (assuming the TCC capacity is actually the culprit) that there is only a slight drop in capacity. That's why personally I would simply shift it manually under those circumstances (and avoid pulling the transmission).

 

[gsbrockman]

TransEngineer....what is your input in regards to the previously addressed complaints and varying rear axle ratios, given the fact all '13 and newer 3500 SRW's are 3.42 and DRW's have the option of 3.73's and 4.10's???

 

[Brocky]

Ram4Sam
I also have had the slight shudder on the 1-2 shift with my 3500 on occasion. Never anything constant or everytime.. Have learned to sorta feather the throttle a little more until after the shift.

 

[Ram4Sam]

Ram4Sam
I also have had the slight shudder on the 1-2 shift with my 3500 on occasion. Never anything constant or everytime.. Have learned to sorta feather the throttle a little more until after the shift.

Mine is infrequent, not even an issue. Just an FYI for the conversation......

Sam

 

[Brocky]

Same Here!!

 

[transe]

TransEngineer....what is your input in regards to the previously addressed complaints and varying rear axle ratios, given the fact all '13 and newer 3500 SRW's are 3.42 and DRW's have the option of 3.73's and 4.10's???

Not sure what you're looking for... This thread seems to have a lot of different complaints, and I don't recall seeing any comments about these issues being unique to a particular axle ratio (or SRW vs DRW), but then maybe you've been paying more attention to the signature line specs than I have! Can you be more specific about which specific shudder / complaint you are wondering about, and how you think it might relate to axle ratio?

By the way, be forewarned: My answer will probably be "I have no idea!"

 

[Brocky]

The only thing I see is that the lower ratios 3:73 & 4:10 MIGHT(???) raise the RPM of this 2-3 shift to where there would be less engine lugging causing this "rumble strip" shudder. The same as Trans Eng is saying about locking in 2nd longer to raise RPM's before the shift.

 

[transe]

The only thing I see is that the lower ratios 3:73 & 4:10 MIGHT(???) raise the RPM of this 2-3 shift to where there would be less engine lugging causing this "rumble strip" shudder. The same as Trans Eng is saying about locking in 2nd longer to raise RPM's before the shift.

Negative on that. Shift points are based on output RPM, not vehicle speed. So shifts should occur at the same output (and engine) RPM regardless of axle ratio.

 

[gsbrockman]

Negative on that. Shift points are based on output RPM, not vehicle speed. So shifts should occur at the same output (and engine) RPM regardless of axle ratio.

Interesting.....

 

[HorseMan-AR]

If I manually shift, as you recommend, and the TCC has a small tear, will the issue become worse over time? How much time (or miles) do I have with the existing TC, I guess is what I'm asking (if there's even an issue with it - right now, I know, we are simply hypothesizing).

Yes, the TCC is inside the converter, so to replace the TCC you replace the converter, which requires removing the trans, which should be a one-day (but basically all-day!) job.

All TCCs should be the same, but I'd guess perhaps there is a small tear in one of the seal lips (giving a slight pressure loss, that reduces the capacity) or some other hardware issue that might be causing lower capacity. I would not think it's software-related.

Since apparently the problem only happens when towing up a grade, just after the 2-3 upshift, it would seem (assuming the TCC capacity is actually the culprit) that there is only a slight drop in capacity. That's why personally I would simply shift it manually under those circumstances (and avoid pulling the transmission).

 

[transe]

If I manually shift, as you recommend, and the TCC has a small tear, will the issue become worse over time? How much time (or miles) do I have with the existing TC, I guess is what I'm asking (if there's even an issue with it - right now, I know, we are simply hypothesizing).

That's really impossible to say. I guess I would explain it to your dealer, and have them make a record of the complaint. Tell them you can live with it for now, but want to make sure that if it gets worse in the future, it will be covered under warranty. Hopefully they will be able to work with you on that.

 

[HorseMan-AR]

Thanks again, my fiend. Really appreciate all the feedback. Another question, does the shudder contribute to more extensive wear and tear on other parts of the drive line? Am I going to break something prematurely?

That's really impossible to say. I guess I would explain it to your dealer, and have them make a record of the complaint. Tell them you can live with it for now, but want to make sure that if it gets worse in the future, it will be covered under warranty. Hopefully they will be able to work with you on that.

 

[transe]

Thanks again, my fiend. Really appreciate all the feedback. Another question, does the shudder contribute to more extensive wear and tear on other parts of the drive line? Am I going to break something prematurely?

Actually, no, I would not expect TCC shudder to cause any durability issue. The shudder is caused by the TCC slipping (when the engine torque pulses exceed the TCC capacity, so it's actually going stick-slip-stick-slip very rapidly). So if you think about it, you are actually getting LESS torque into the trans and driveline than you would if the TCC was NOT slipping. When the TCC slips, it acts as a limiter; it will transmit its peak capacity but no more. So if TCC capacity is 900 ft-lbs, and engine spikes are 950 ft-lbs, input torque to the trans will rise to 900 ft-lbs but then will simply hold at 900 as the TCC slips. If the TCC didn't slip, the trans input would go up to the full peak of 950 ft-lbs.

One other possible concern would be heat generation within the converter, due to the TCC slippage. A slipping clutch generates heat, and the amount of heat is directly related to torque level, and slip speed. Now in the TCC, torque level will be high (say 900+ ft-lbs), but the slip speed is low. Because the TCC is not slipping continuously (at like 300 RPM) but instead is just slipping in small increments (a few degrees with each pulse), the slip speed is usually just a few RPM. So the overall amount of heat generated is not extreme. Plus the event normally occurs for only a brief period (maybe a second, before you tip out or downshift). So heat is not a big concern either.

Now I'm not suggesting that you should just ignore the TCC shudder and allow it to continue for an extended period. I would definitely avoid it by downshifting or backing off the throttle. I'm just saying that brief TCC shudder events should not be big concern from a durability standpoint.

 

[Bug Out]

After reading this post, I realize that the 2013 Mega cab I have, has a case of "turn shudders", loaded at take off speed on 90 degree turns. The two other RAMS, 2012-2013 did not do this. I am going to try some LS fluid to see if it helps or stops.. ( Now If I can only get it to quit overheating #@$%!)