jdm svx trans, will it work?

[TomsSVX]

Ok clarification has not worked thus far. So lets try a different approach.

When the solenoid recieves a full 12v signal in a US trans it drives only the front wheels. When a full 12v signal to a VTD trans is sent it locks to full 4wd. So right now when the VTD tcu is sending the signal to tighten the grip between the front and back wheels it is infact breaking the grip and creating a FWD car. SO this means when the US solenoid is not seeing a signal it is locking the center diff. When the VTD trans sees no signal it is opening the center diff. So in situation where the TCU commands to open the center diff it is effectively closing it. By fitting the JDM solenoid it will effectively reverse the already backwards function and create the proper situation where needed.

Now, IF he had a JDM car with a front diff mounted speed sensor #2 like I had originally thought, a US TCU would fix the issue right out. He does not. He has the AU style box with the internal speed sensor #2. Now location of the sensor doesn't matter but the expected signal out of them is radically different, not to mention the proper wiring to the sensors is also very different. So with great differences in signal and wiring it is not worth it to try and make the US TCU work when the solenoid will fix the issue much faster and easier.

If that doesn't make sense, I don't know what else to say

Tom

[Trevor]

Originally Posted by TomsSVX

Ok clarification has not worked thus far. So lets try a different approach.

When the solenoid recieves a full 12v signal in a US trans it drives only the front wheels. When a full 12v signal to a VTD trans is sent it locks to full 4wd. So right now when the VTD tcu is sending the signal to tighten the grip between the front and back wheels it is infact breaking the grip and creating a FWD car. SO this means when the US solenoid is not seeing a signal it is locking the center diff. When the VTD trans sees no signal it is opening the center diff. So in situation where the TCU commands to open the center diff it is effectively closing it. By fitting the JDM solenoid it will effectively reverse the already backwards function and create the proper situation where needed.

Tom, The suggested set up will unfortunately not work. You have neglected to take into account the 36:64 F/R ratio of the VTD system using a LSD, whereas the USDM uses a centre clutch and fixed front drive. This is the guts of the situation. ---

#1 Normal VTD system. --- When increased front bias is required, the pulse length will be increased, in order to close a N/O solenoid, thus increasing pressure, to close a LSD clutch. The TCU will be programmed to increase the pulse lentgth.

#1 With Alex' car. --- When increased front bias is required the same increased pulse length command, will open a N/C soleoid, thus reducing pressure, to open the centre clutch. The TCU will be programmed to increase the pulse lentgth.

#2 Normal VTD system. --- When increased rear bias is required, the pulse length will be reduce, in order to open a N/O solenoid, thus reducing preasure, to open a LSD clutch. The TCU will be programmed reuuce the pulse lentgth.

#2 With Alex' car. --- When increased rear bias is required, the same reduced pulse length command, will close a N/C solenoid, thus increasing pressure, to close the centre clutch. The TCU will be programmed reuuce the pulse lentgth.

The above shows that at present the sequence is as required and does not require the change in solenoid as you claim. However it is likely that the existing VTD programme will be unsuitable, given the different characteristics of the LSD and central clutch. But one never knows and the binding reported, could very well be due to a fault in the used transmission purchased.

Now, IF he had a JDM car with a front diff mounted speed sensor #2 like I had originally thought, a US TCU would fix the issue right out.

As I have no data on the speed sensor arrangement in the USDM cars, I am unable to comment and accept that you are no doubt correct regarding the differences.

He does not. He has the AU style box with the internal speed sensor #2. Now location of the sensor doesn't matter but the expected signal out of them is radically different, not to mention the proper wiring to the sensors is also very different. So with great differences in signal and wiring it is not worth it to try and make the US TCU work when the solenoid will fix the issue much faster and easier.
If that doesn't make sense, I don't know what else to say.
Tom

Changing the solenoid will not fix anything, but just the opposite as shown above. In any event, the speed sensor issue would appear to write off using the us transmission, unless a special TCU is developed, which can hardly be justified. Particularly as changing the original transmission is very much a disadvantage.

I hope Phil will provide his expert comments regarding the TCU.

I wonder if there is any hope of money back from the US supplier, due to incorrect advice regarding suitability?

Damn! Trevor

[NiftySVX]

For the record
My point in posting all that garbage was to try and take the technical talk out of it and just propogate the theory that the two solenoids operate essentially opposite but that was already stated by someone previous. I couldn't articulate this properly because I don't think everyone agrees on how it works, which I originally assumed. I was trying to get everyone to the same page on how the US car works. It's just a calculation like anything else in a computer.

Inputs of certain values based on what I called a "map" but perhaps should have called a table in the TCU lead to an output of a certian value, which indirectly causes the torque split, where a difference in front and rear output RPMs constitutes wheel slip. That's just.. how it works. Obviously it is not a person and cannot actually anticipate anything. They don't call it "clervoyant AWD"

[TomsSVX]

Originally Posted by Trevor

Tom, The suggested set up will unfortunately not work. You have neglected to take into account the 36:64 F/R ratio of the VTD system using a LSD, whereas the USDM uses a centre clutch and fixed front drive. This is the guts of the situation. ---

#1 Normal VTD system. --- When increased front bias is required, the pulse length will be increased, in order to close a N/O solenoid, thus increasing pressure, to close a LSD clutch. The TCU will be programmed to increase the pulse lentgth.

#1 With Alex' car. --- When increased front bias is required the same increased pulse length command, will open a N/C soleoid, thus reducing pressure, to open the centre clutch. The TCU will be programmed to increase the pulse lentgth.

#2 Normal VTD system. --- When increased rear bias is required, the pulse length will be reduce, in order to open a N/O solenoid, thus reducing preasure, to open a LSD clutch. The TCU will be programmed reuuce the pulse lentgth.

#2 With Alex' car. --- When increased rear bias is required, the same reduced pulse length command, will close a N/C solenoid, thus increasing pressure, to close the centre clutch. The TCU will be programmed reuuce the pulse lentgth.

The above shows that at present the sequence is as required and does not require the change in solenoid as you claim. However it is likely that the existing VTD programme will be unsuitable, given the different characteristics of the LSD and central clutch. But one never knows and the binding reported, could very well be due to a fault in the used transmission purchased.



As I have no data on the speed sensor arrangement in the USDM cars, I am unable to comment and accept that you are no doubt correct regarding the differences.



Changing the solenoid will not fix anything, but just the opposite as shown above. In any event, the speed sensor issue would appear to write off using the us transmission, unless a special TCU is developed, which can hardly be justified. Particularly as changing the original transmission is very much a disadvantage.

I hope Phil will provide his expert comments regarding the TCU.

I wonder if there is any hope of money back from the US supplier, due to incorrect advice regarding suitability?

Damn! Trevor

Hold the phone here a minute. There is no way to increase the front bias of USDM transmission. It is a direct drive to the front pinion shaft from the output shaft. All the solenoid does it engage the rear wheels when called for, effectively increasing the rear bias. I think this is where we are being separated in theory.

I would need to take a closer look at the JDM tailshaft I have on the shelf which is VTD and make more sense of what I originally thought. But the way I see it is, the VTD transmission is essentially a purely mechanical differential and it will simply vary the lock between front and rear as commanded.

While it will not make his car run 100% like the proper TCU programming would, it would sure as hell help him more than any other option. This has been my point all along. if he continues driving it this way it will shear the transfer drum off of the output shaft and he will lose his AWD all together. Its not going to be right no matter which way he goes but all I was trying to do is give him the easier path.

Try the solenoid, if it does not work, then you will need to invest more time and money into changing the entire wiring of the car to accept a USDM TCU. Or just getting the right trans from someone who knows what is going on

Tom

[b3lha]

This is a very interesting discussion for sure.

I think, if it was my car, I would not go any further down this road. It's going to be fiddly, expensive and there's a good chance it may not even work properly at the end of it. I would sell the incorrect parts, find the correct parts for the car and fix it properly. It just makes a whole lot more sense in the long run.

[Trevor]

Originally Posted by TomsSVX

Hold the phone here a minute. There is no way to increase the front bias of USDM transmission. It is a direct drive to the front pinion shaft from the output shaft. All the solenoid does it engage the rear wheels when called for, effectively increasing the rear bias. I think this is where we are being separated in theory.

Hold the phone indeed. The front bias can be increased from any setting, other than lock up. There is no suggestion that the front can be made to exceed the rear. Bias --- off my Mac. " in favor of or against one thing".

I would need to take a closer look at the JDM tailshaft I have on the shelf which is VTD and make more sense of what I originally thought. But the way I see it is, the VTD transmission is essentially a purely mechanical differential and it will simply vary the lock between front and rear as commanded.

No need to check that shelf. It is a difficult system to get a grip on. When the proportional LSD has an only partly locked clutch in parallel to it, there are two combined forces involved, i.e. that from an adjustable slipping clutch and from a proportional LSD. The action of the proportional LSD remains at 36f:64r.

This results in a rather complicated formulae covering front/rear split, viz ---

When the front wheel RPM exceeds the rear drive RPM, (output torque to the rear) = [0.636X(input torque to the LSD)] + (adjustable torque transmitted via the clutch). While (output torque to the front) = [0.364x(input torque to the LSD)] - (adjustable torque transmitted via the clutch).

While it will not make his car run 100% like the proper TCU programming would, it would sure as hell help him more than any other option. This has been my point all along. if he continues driving it this way it will shear the transfer drum off of the output shaft and he will lose his AWD all together. Its not going to be right no matter which way he goes but all I was trying to do is give him the easier path.

Try the solenoid, if it does not work, then you will need to invest more time and money into changing the entire wiring of the car to accept a USDM TCU. Or just getting the right trans from someone who knows what is going on

N.B. Changing the solenoid in effect, reverses what is at present correct, as I have gone to great deal of trouble to describe.

Just how will forces be generated in excess of normal, such that ---"it will shear the transfer drum off of the output shaft and he will lose his AWD all together"? Only a clutch is involved and a constant, or near constant, signal would be required to lock this up, as will only be transmitted if the special fuse is inserted. This will provide a locked up F/R drive as per the original VTD system.

Man oh man, this debate is taxing my literary and keyboard skills something horrible, as well as my hole in the head. The time and effort required is now over the fence.

[Trevor]

Originally Posted by b3lha

This is a very interesting discussion for sure.

I think, if it was my car, I would not go any further down this road. It's going to be fiddly, expensive and there's a good chance it may not even work properly at the end of it. I would sell the incorrect parts, find the correct parts for the car and fix it properly. It just makes a whole lot more sense in the long run.

Thanks Phil,

You have confirmed my thinking.

The debate has gone on long enough, and the other parties should simply confirm understanding.

Sincere regards, Trevor.

[TomsSVX]

If a US tranmsission is indeed binding by applying pressure to the transfer clutches to engage the rear wheels (as Alex's is doing now) it will overtime over tax that integrity of the drum on the output shaft and shear it from the output shaft leaving him with no rear drive at all. It needs to be addressed sooner than later.

So lets just ask this question. At light throttle (cruising) does the VTD trans have a long signal length or short. Under heavy throttle does the singal length become shorter or longer as per the programming for the VTD trans. I can answer those questions for the US trans but not for the VTD system

Tom

[oab_au]

Originally Posted by TomsSVX

If a US tranmsission is indeed binding by applying pressure to the transfer clutches to engage the rear wheels (as Alex's is doing now) it will overtime over tax that integrity of the drum on the output shaft and shear it from the output shaft leaving him with no rear drive at all. It needs to be addressed sooner than later.

So lets just ask this question. At light throttle (cruising) does the VTD trans have a long signal length or short. Under heavy throttle does the singal length become shorter or longer as per the programming for the VTD trans. I can answer those questions for the US trans but not for the VTD system

Tom

Alex now has the 'diff lock fuse' fitted, this supplies a 95% signal that has turned off the US clutch, to FWD.

The VTD on light throttle cruise, has a low 5/10% Duty cycle signal. On a full throttle condition it is a high 90/95% signal.

Harvey.

[Trevor]

Originally Posted by TomsSVX

If a US tranmsission is indeed binding by applying pressure to the transfer clutches to engage the rear wheels (as Alex's is doing now) it will overtime over tax that integrity of the drum on the output shaft and shear it from the output shaft leaving him with no rear drive at all. It needs to be addressed sooner than later.

Only a clutch is involved and a constant, or near constant, signal would be required to lock this up, as is only likely to be transmitted if the special fuse is inserted. Only this should provide a locked up F/R drive as per the original VTD system. There should be near normal control of the centre clutch.

However I do agree that there is possible danger, but it has been pointed out that a change of TCU programme is certainly desirable.

I thought that I covered this aspect of the situation in my post, but sorry if this was not absolutely clear.

Under normal driving conditions, why would the VTD TCU still fitted, call for a constant lock up, completely defeating the action of the normally associated, centre LSD? As of now, this would be required in order to fully lock up the clutch at present in use.

So lets just ask this question. At light throttle (cruising) does the VTD trans have a long signal length or short. Under heavy throttle does the singal length become shorter or longer as per the programming for the VTD trans. I can answer those questions for the US trans but not for the VTD system

Under a light throttle, the VTD would transmit a relatively short pulse signal, in order to provide an open and fully working, centre LSD.

Under a heavy throttle, the VTD would surely transmit only a shortened pulse signal, in order to retain a partly open and operative, centre LSD. However there would peobably be bias towards the rear. Refer to the formulae I provided.

A completely locked LSD should only be possible/likely, if there was complete wheel slip, simultaneously both front and rear. This would comprise a drastic action and would only occur if the wheels were slipping absolutely freely. In which event there would be only limited torque resistance applied via a clutch to the rear wheels.

I say again ----- Man oh man, this debate is taxing my literary and keyboard skills something horrible, as well as my hole in the head. The time and effort required is now over the fence.

P.S. Check with Ron. I am sure that he will explain that whipper snappers, should not over tax the brains of old farts.

[TomsSVX]

If the duty rate is 5% under light throttle and 95% under heavy throttle it would indeed be the opposite as the US trans. Like I said, worth a try rather than pulling the unit and replacing it

Tom

[Trevor]

Originally Posted by TomsSVX

If the duty rate is 5% under light throttle and 95% under heavy throttle it would indeed be the opposite as the US trans. Like I said, worth a try rather than pulling the unit and replacing it

Tom

I did not suggest the rates you have stated, as being a constant situation covering the VTD. The centre LSD could be left open under many normal situations, including heavy throttle. The point is that it should not be fully closed under normal conditions. There is no a straight reversal as a result the change in transmissions.

Where did you previously say, "Like I said, worth a try rather than pulling the unit and replacing it"? I have mentioned this as a valid possibility. This is the critical issue and we must be confident in what is advised.

I have just received a PM from Alex as he is still in limbo. He must be advised accurately regarding the issue.

Cheers, Trevor.

[oab_au]

Well advise him that either, you will send him the normally open solenoid that he wants, or you will advise him of where he can order it.

Harvey.

[Trevor]

Originally Posted by oab_au

Well advise him that either, you will send him the normally open solenoid that he wants, or you will advise him of where he can order it.

Harvey.

Explain exactly how this will effect the set up he has. If you can show how it will be satisfactory, I will have the one I purchased for Alex and now in my hand, in the airmail like a flash.

[oab_au]

Originally Posted by Trevor

Explain exactly how this will effect the set up he has. If you can show how it will be satisfactory, I will have the one I purchased for Alex and now in my hand, in the airmail like a flash.

You have held Alex for ransom long enough.
I have no intention of explaining anything to you. You lost my respect a long time ago.

Harvey.