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#46
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Re: jdm svx trans, will it work?
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First they will detect a difference in wheel speed between the two ends, and apply the clutch, in line with the difference, to stop any wheel spin. Secondly they will apply the clutch to prevent wheel spin, depending on, Throttle opening, road speed and gear position. 1st gear, low speed, full throttle will apply the highest pressure. 4th gear, high speed, light throttle, will apply the lowest pressure. The torque split between the two boxs, does not come into it. The VTD will do the most variation, but this is due to the epicyclic ratio difference, not to the maps. I agree, using the appropriate TCU for the type of box, is the best, but there are some combinations that are not that easy to match. The wiring, and speed sensor differences, can make the swapping of the solenoids, the most cost effective option. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#47
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Re: jdm svx trans, will it work?
Yes i have to go back on the old plan and swap the tranny. Now i just need the parts.
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Alexander (Norway) My subarus: 1992 Svx LSI 5-MT(3.54) 1998 Legacy BG 2.5L GX |
#48
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Re: jdm svx trans, will it work?
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Sorry to just jump in here, but is the solenoid's little valve body identical in the two setups? I really wish I had known this before I spent all the money on my USDM trans. I would have just put the US speed sensor and the US solenoid and rebuilt burnt up VTD box and put it in my car instead.
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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#49
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Re: jdm svx trans, will it work?
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The above vague statement, is to say the least misleading and partly incorrect, refer preceding post #48. Adding to the confusion, Posts #5, #16, are entirely incorrect. Consider the way the transmission actually functions. --- USDM System. An increase in the length of the 50 cps PWM signal pulses, or a constant signal, opens the normally closed C bleed solenoid valve. As a result pressure to the centre transfer clutch is reduced and the rear drive can be interrupted to a point where drive is only to the front Wheels. Reducing the length of the pulses, or a near zero signal to the normally closed C bleed solenoid valve, results in the solenoid closing. As a result pressure to the centre transfer clutch is increased, so that drive to the rear can be applied together with the front, to a point of lock up. Alteration of the pulse length provides front rear torque control. Unfortunately this system does not allow drive force to the rear to exceed that to the front. Hence reports of understeer. JDM VTD System. An increase in the length of the signal pulses, or a constant signal, closes a normally open C bleed solenoid, increasing pressure to the parallel multi plate LSD clutch, therefore over riding the LSD to a point of lock up. Reducing length of the signal pulses, or no effective signal, opens a normally open C bleed solenoid, reducing pressure so that the clutch is released. Drive is then via the centre differential with a split of 36.4% front, 63.6 rear, due to the included LSD gear ratio. Alteration of the pulse length provides front rear torque control, up to a point of lock up. The very different arrangement USDM/JDM, explains the reason for problems involving front rear binding, if the appropriate TCU and or matching solenoid is not fitted. Refer report by Steve in post #14, as follows:- “I have an update, everything is installed, tranny, rear gears with SVX LSD. I drove the car down the road and all was well at low speed, when i needed to turn it felt strange, kinda like a 4x4 truck in 4wd on pavement. So i believe the center diff is locked or something.” I commiserate with Steve. Alex and now Nate. also require a thought. This now horribly confusing and misleading thread, is of no credit to the network.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! Last edited by Trevor; 07-21-2009 at 12:04 AM. Reason: Typo |
#50
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Re: jdm svx trans, will it work?
If that transmission is trashed then I could simply use the extension housing and its contents to make my trans a VTD. this excites me greatly. I wonder How much it would cost to have the necessary parts shipped, assuming the owner has no use for them.
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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#51
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Re: jdm svx trans, will it work?
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Language barrier here Nifty. When you say "trashed" you mean it is broken, unsuitable for use, not fully working. I think when Alex says "trashed" he means the people who took it out sent it away as trash to be scrap metal. I don't think he physically has the original gearbox any more. Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#52
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Re: jdm svx trans, will it work?
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Alexander (Norway) My subarus: 1992 Svx LSI 5-MT(3.54) 1998 Legacy BG 2.5L GX |
#53
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Re: jdm svx trans, will it work?
OH MAN! FML!
I was so excited there, briefly. I will get my hands on a vtd setup, soon though. I have plans for my FWD trans to become a VTD unit with the 3.70 rear ratio. This goes along with my policy to never throw any part of an SVX away no matter how badly damaged or useless!
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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#54
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Re: jdm svx trans, will it work?
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You can work around this by wiring a potentiometer to the Atmospheric Pressure pin of the TCU. You can then vary the aggressiveness of the shifting by turning the potentiometer. It will select the Normal, LowPres1, LowPres2 or Power shift maps as described in the Gear Shift Maps thread. It's like having a 4 position power mode switch.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#55
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Re: jdm svx trans, will it work?
No Baro sensor in the other ECU's??? Thats a surprise. That would be interesting to do though with the pot.
Tom |
#56
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Re: jdm svx trans, will it work?
I'm just gonna guess that everyone is assuming or knows that the programming in the TCU just goes ahead and applies the clutch if there is a different value from front-rear that qualifies as a slip, like if speed one does not equal speed 2 then apply, but, in ACT-4 there is no possible way that the rear wheels would ever rotate faster than the front when power is being transmitted from the engine. If the computer compares rear wheel speed as a value expressed as a difference from front wheel speed that can only be 0 or negative, then who knows how it will act when the rear wheel speed is greater than front wheel speed.
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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#57
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Re: jdm svx trans, will it work?
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Maybe read the two speeds, subtract one from the other, the result, either positive or negative, is the amount of pressure that is sent to the clutch. I believe that more than 20% difference is considered 'wheel spin'. Under this amount, the car is turning, and the US transfer clutch will allow slip. The VTD clutch will allow the difference, as the torque will shift to the front wheels, due to the rotational difference of the epicyclic gear ratio. This is where the main difference is between the two drives. The US Transfer system will always maintain the same torque split between the two ends through a corner, as long as the throttle is constant. The VTD will vary the torque between the two ends, increasing the torque feed to the front as the car turns into the corner. Any body that has driven a VTD car will know how that, turning into a tight turn, the front wheels pull the front around the turn, with no sign of understeer. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#58
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Re: jdm svx trans, will it work?
Any rear wheel speed that exceeds the allowance for turning will result in full line to the transfer clutch until the two speeds become equal. You can observe this with a line pressure test at the extension housing. From my tests and experiments with the transfer clutch, which is fun to watch, is really dynamic in nature and is always changing the pressure as you drive it. However, when i had it rigged up, slipping the front wheels would override the predictive modeling logic and just try and lock the clutch up as best it can with available line.
as a side note: This is one major area that is drastically improved by a throttle body mod that raises base line. The AWD is much more even split when the line is higher.
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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#59
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Re: jdm svx trans, will it work?
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The outer case/body of the two solenoids i.e. normally closed and normally open, is the same, which makes them interchangeable. However, understandably you may have become confused by incorrect statements within this thread. A US type N/C solenoid must not be used with a VTD box.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#60
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Re: jdm svx trans, will it work?
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The understeering reported in respect of the US cars is the result of excessive front wheel bias, as it is not possible under any circumstance, for rear torque to exceed that at the front. Front wheel drive causes under steer, when the slip angle at the font increases due to the power being applied. This characteristic doe not occur in respect of VTD models. Power can/will be applied to the rear in excess of the front, when power is used in a corner, resulting in the increase in any slip angle occurring at the rear rather than the front.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
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