DCT Performance?

[mdmoore23]

DCT or extremely torque sensitive. I believe that was one of the tuning problems with the new 5.2. Keeping the torque to a minimum while still making the correct horsepower. These transmissions will be awesome stock but could be a potential nitemare when torque levels increase.

The GT500's DCT is rated at 664 lb. ft. I know many transmissions can survive well beyond their rated torque capacities. Hopefully the GT500 will be no different. Because that torque will be exceeded quickly when people start modding.

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[Hack]

You are completely correct. I was talking more about the management at lower speeds. That’s why I talked about tuning.

DCT don’t have the ability to slip like a normal torque converter or even manual transmission so over torque situations in shifts at lower speeds are a serious consideration. You want max horsepower at a 7300 rpm shift but a WOT shift at 5250 may have a different strategy.

While this motor may only produce 625ft lbs of torque, without the ability to put excesses torque somewhere during shifts on a sticky surface things will break. DCT are known for a lot of things but torque handling is not one of them.

DCT clutches definitely have the ability to slip. Not like a torque converter slipping all the time with no wear, but they do have that ability. My understanding is soft/slow clutch engagement is the reason why the clutches are cooled by transmission fluid and why Ford says there are "thermal events". Heat is generated by friction, which to me means the clutches have at least some amount of slip designed in.

Edit: it's the system including the clutches and the associated mechatronics that run the clutches that causes and controls the slip.

 

[BlackandBlue]

Has anyone heard or read why they didn't use the 10 speed? That trans seems to have proven itself to be pretty robust and shift times aren't far off a DCT.

Heat Is the biggest reason and performance is a close second. A DCT is a manual automatic transmission so heat generation is kept to a minimum while keeping the performance of an automatic.

 

[BlackandBlue]

DCT clutches definitely have the ability to slip. Not like a torque converter slipping all the time with no wear, but they do have that ability. My understanding is soft/slow clutch engagement is the reason why the clutches are cooled by transmission fluid and why Ford says there are "thermal events". Heat is generated by friction, which to me means the clutches have at least some amount of slip designed in.

Edit: it's the system including the clutches and the associated mechatronics that run the clutches that causes and controls the slip.

I think longevity is a concern when you start slipping clutches to bleed off excess torque.

You have a 12”x13” section for even gears and a 12” x 11.5” clutch for odd gears. Would it be exceptable to have the same clutch replacement intervals as a manual clutch?

I had a buddy with a GTR that always swore that it took the right group of highly skilled gnomes to make his transmission work right. I hope this is not the case for the GT500.

 

[nastang87xx]

DCT clutches definitely have the ability to slip. Not like a torque converter slipping all the time with no wear, but they do have that ability. My understanding is soft/slow clutch engagement is the reason why the clutches are cooled by transmission fluid and why Ford says there are "thermal events". Heat is generated by friction, which to me means the clutches have at least some amount of slip designed in.

Edit: it's the system including the clutches and the associated mechatronics that run the clutches that causes and controls the slip.

And since it's a wet system, the clutches don't get beat on as hard when they do slip. You're absolutely right, DCT's 100% can slip and do slip. Many DCT cars have strategies in them to slip the clutch to replicate the function of a torque converter auto.

 

[BlackandBlue]

And since it's a wet system, the clutches don't get beat on as hard when they do slip. You're absolutely right, DCT's 100% can slip and do slip. Many DCT cars have strategies in them to slip the clutch to replicate the function of a torque converter auto.

I apologize for not being more clear. A clutch is obviously a slippable device. The problem with slipping clutches is heat generation and clutch wear. An automatic takes care of this with a torque converter. A manual has replaceable disk that takes the slipping.

Slipping 200hp is the same as putting a 150 kw heater inside a transmission. You can slip some but heat and wear quickly become a serious problem.

My original post was pointed towards the problems with DCT being torque sensitive. This problem is from the lack of slipping ability Vs other styles of transmissions.

I personally believe this will be a very good transmission when the car is kept is stock form. I just don’t think Ford was able to put the parts inside it that will allow the doubling of its torque capacity like the a10 is able to handle.

 

[Hack]

Automatic transmissions have clutches that absolutely also do slip. When an automatic transmission shifts, the softness/firmness of the shift is due to how much clutch slippage is allowed.

So, in a normal passenger car, the auto transmission clutches slip on every single shift. Different clutches for every shift rather than two clutches alternating on every other shift, but yes automatic transmissions have a very similar issue to a DCT in this regard.

Edit: I would go so far as to say the technology is/could be very very similar from an engineering design standpoint.

 

[BlackandBlue]

Automatic transmissions have clutches that absolutely also do slip. When an automatic transmission shifts, the softness/firmness of the shift is due to how much clutch slippage is allowed.

So, in a normal passenger car, the auto transmission clutches slip on every single shift. Different clutches for every shift rather than two clutches alternating on every other shift, but yes automatic transmissions have a very similar issue to a DCT in this regard.

Edit: I would go so far as to say the technology is/could be very very similar from an engineering design standpoint.

DCT are a manual transmission that has been modified to shift automatically. It has synchronizers. It has almost nothing in common with a automatic transmission. It shouldn’t be compared to an automatic in any way except for automatic shifting.

Pure automatics have the torque converter to absorb shock and allow torque reduction on shifts without much clutch or band wear. DCT don’t.

Edit: When I am talking about wear or slippage I am speaking in terms of full throttle. IE the designed limits of the machinery.

Please watch video.

 

[V00D00]

Like most have said, its tq, keeping the tq low, but also its an rpm issue.

However, i dont believe many tremecs are weak. So id be betting the internals are very robust, and can handle lots of power.

Its the clutches that will go 1st, obviously, and hopefully all that needs to be replaced.

The issue, and i think the restraint, is that the heavy or more plated clutch baskets, make daily driving less and less pleasurable.

My educated guess, is after 800wtq, a clutch upgrade will be required, and thats all. At least until one cross 4 digit power

 

[geoking]

So if/when someone grenades the DCT who is going to fix it (besides Ford)? Just wondering if there are DCT performance companies/products out there? I assume at this point being so green(Ford/Tremec) we wont have much to choose from until the market catches up. I am not even sure what 'performance' items there are for DCT? clutch packs? cryo-gears? hi-po servers? tunes, valve bodies......just wondering what is done to a DCT to handle high HP?

DCT scares me from a cost and knowledge perspective, I assume at some point a few years from now it will be more 'normal' to work on DCT just wondering if the traditional Tranny business/sites will change with the times.

After reading your post, I thought about a previous car that I owned. ( an early STS Cadillac) When it first appeared in the market place, dealers were unable to repair the front wheel drive transmission. As such, a swap program was instituted.
If you bring a GT500 in with a defective DCT, I would venture to "guess" that the entire unit will be swapped out with a different tranny. The defective unit would most likely go back to Tremec for rebuild and go into a swap program. ( pure speculation on my part). With folks talking about upping the engines output, should we be concerned about the DCT holding up? Why not just call Tremec and ask them? I just hung up from a call with Tremec's support line and asked if they offer a more robust DCT for aftermarket sales? No sir, we currently will not offer an aftermarket replacement. Can you make my new GT500 more robust to handle 1200 HP? No Sir. How about 1000 HP? No Sir. The DCT has been rated at 700 ft lbs of torque and we currently do not have an offering beyond that. What do you suggest? Maybe you should call Detroit gear and see if they can help you? Thank you very much.

Regards,
George

 

[BlackandBlue]

Like most have said, its tq, keeping the tq low, but also its an rpm issue.

However, i dont believe many tremecs are weak. So id be betting the internals are very robust, and can handle lots of power.

Its the clutches that will go 1st, obviously, and hopefully all that needs to be replaced.

The issue, and i think the restraint, is that the heavy or more plated clutch baskets, make daily driving less and less pleasurable.

My educated guess, is after 800wtq, a clutch upgrade will be required, and thats all. At least until one cross 4 digit power

In your experience after replacing the clutches what is the next failure point?

 

[Hack]

DCT are a manual transmission that has been modified to shift automatically. It has synchronizers. It has almost nothing in common with a automatic transmission. It shouldn’t be compared to an automatic in any way except for automatic shifting.

Pure automatics have the torque converter to absorb shock and allow torque reduction on shifts without much clutch or band wear. DCT don’t.

Edit: When I am talking about wear or slippage I am speaking in terms of full throttle. IE the designed limits of the machinery.

Please watch video.

You quoted my post, so I assume you are trying to refute what I said?

Automatic transmissions when they were purely mechanical with no electronics used pressure modulators, springs and pistons that operated to engage the clutches. Now it's done electronically, but the same things are happening. Torque converters do absorb some shock, but there is also a lot of shock that is absorbed through GRADUAL application of the clutches to engage the next automatic transmission drive speed. During normal driving, the engine is spinning at an RPM higher than the torque converter's stall speed, and so the torque converter doesn't do what you are saying.

Based on your posts, you've possibly never ridden in an older car with an automatic with a "shift kit". With older auto transmissions, you would change out some orifice sizes in the valve body and/or springs, etc. and then you could get very firm shifts. I had a buddy with a shift kit in his car (not a high powered vehicle) and it would chirp the tires on shifts. It still had the torque converter, of course, but the gradual application and slipping of clutches inside the transmission was reduced. And he didn't have the maximum firmest possible shift kit, either.

In a DCT, when you are stopped and you apply the accelerator pedal, the computer slowly engages the clutches, allowing them to slip so that there isn't a shock when the clutches engage. If the DCT dumped the clutch it would either kill the engine or spin the tires.

This slipping of clutches is necessary both in an automatic and in a DCT in order to have acceptable NVH and reduce shock in the drive line and to the passengers.

I believe the GT500 will allow significant slippage on gear changes in order to soften the impact of shifts and prevent upsetting the car during cornering maneuvers. In drag mode, the slippage will probably be reduced, but it will still be there, because spinning isn't winning. The last thing you want is the shock from the DCT shifting to break the tires loose. That will slow the car down.

 

[BlackandBlue]

I do know what tighting the cable means. We always said “give it another click”.

I think the common misconception about torque converters is that in a stalled, non-locked condition they don’t slip. They do. The fluid is absorbing the peak force allowing the clutches to take a stable load and shift gears.

A true automatic has a viscous damper that allows much high peak torque load at shift points vs a manual transmission.

Peak torque is what breaks stuff. My guess is the DCT was the single biggest time sink in the GT500 program.

I am not trying the refute what you are saying. You are just comparing an automatic to a DCT when we should be comparing it to a manual trans.

 

[V00D00]

In your experience after replacing the clutches what is the next failure point?

Shafts, gearsets, then you have the little shit, bearings and things i dont even know what they are called. But gearsets and shafts are the biggie's

 

[Hack]

I do know what tighting the cable means. We always said “give it another click”.

I think the common misconception about torque converters is that in a stalled, non-locked condition they don’t slip. They do. The fluid is absorbing the peak force allowing the clutches to take a stable load and shift gears.

A true automatic has a viscous damper that allows much high peak torque load at shift points vs a manual transmission.

Peak torque is what breaks stuff. My guess is the DCT was the single biggest time sink in the GT500 program.

I am not trying the refute what you are saying. You are just comparing an automatic to a DCT when we should be comparing it to a manual trans.

Yes, I agree a stalled torque converter will still slip. However, the clutches in the automatic transmission must still slip quite a bit in order to provide soft, livable shifts that don't break the tires loose. In that respect, slipping clutches are needed both in the DCT and in a typical automatic in order to reduce the harshness of shifts.

I think the clutches in the GT500 DCT are more like those in an automatic transmission than the clutch in a manual transmission. They are wet, have multiple plates and are designed to allow more slipping. The fluid on the clutches is there to carry heat away so that the clutch can slip more without being damaged or having excessive wear.

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