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  #16  
Old 03-14-2005, 07:37 PM
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Quote:
Originally Posted by oab_au
The flaring that Chike had, is not the same as the typical flaring, that we get on the 2nd/3rd gear change. When this happens the band just releases early, before the high clutch has applied. This does not wear the band as it is not slipping.

In Chikes case the band is slipping big time. What happens is, in first the forward clutch is on, to go to 2nd, we only have to apply the band to brake the front sun gear to a stop. This gives 2nd. What has happened is that when the TCU sent the signal to change, the band was applied but slipped too much, to stop the drum from spinning. It was only when the engine 'over rev cut out' came on to cut the torque, that the band could stop the drum from spinning. So from the time the signal for change was sent at 5400 rpms till the torque was cut at 5750, the band was burning up.

Why this happened is the way the changes are set up to take place. Subaru has allways tried to have the changes as smooth as possible, with no thump. It is this action that has caused the problem that Chike has found.
When the TCU sends the signal to the shift solenoid, it switches to allow a pilot pressure to move the shift spool valve across, to open the ports and direct line pressure, to the brake band servo, to apply the band.

If this was all that happened, there would be a big thump as the band suddenly stopped the sun gear drum. To soften the change there is another unit called the 2A accumulator. This is a little hydraulic cylinder, with a piston and spring, that is connected into the line going to the band servo. It acts to soften the application of the line pressure on the band servo. The pressure builds up gradually as the accumulator piston is forced back against the spring. This causes the band to slowly apply to change into 2nd. without a thump.

What needs to be done is to send the valve body away to one of the good auto box builders (DRG, Level 10) . Get them to alter the spring or orifices, to allow the pressure to rise quicker, so the band is applied with less time to slip. I reckon you would only have to explain the problem, for them to know what to do. This modification will make the changes harder,and the box will not be as smooth, but it will make it survive the treatment longer.

Harvey.
I was thinking some more about what you wrote Harv, and before I spend $500 in modifying my vave body, I think it would be best for me to make sure my brake band is at the correct setting at the time I install the Legacy Outback trans I have on order.

In my Impreza 4.11 trans, I drove around and raced on it with the brake band not set at the correct position (tighter than it should have been). If I had the band set correctly, I'm sure my trans would have been fine up to this point...

Either way, having a modified valve body wouldn't hurt for racing purposes, but I just can't afford it at this time.

-Chike
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  #17  
Old 03-14-2005, 07:51 PM
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Quote:
Originally Posted by oab_au
.

What needs to be done is to send the valve body away to one of the good auto box builders (DRG, Level 10) . Get them to alter the spring or orifices, to allow the pressure to rise quicker, so the band is applied with less time to slip. Harvey.
Harvey, do you know which orifice to enlarge?
Level 10 wanted something like $750.00 just to redo the valve body.
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  #18  
Old 03-14-2005, 10:25 PM
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Another question to Harvey. Back many years ago, we used to R&R the spring on MOPAR Torqueflight automatic transmissions, stretching it a bit while it was out. Effects didn't last too long, but it did work to stiffen up the shifts for a while.

So, using that principle, and what I think you're saying above, all that would be needed is the same size spring, but with a bit more compression strength...did I get it, or did I miss the boat yet again?
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  #19  
Old 03-15-2005, 07:21 PM
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Quote:
Originally Posted by lee
Another question to Harvey. Back many years ago, we used to R&R the spring on MOPAR Torqueflight automatic transmissions, stretching it a bit while it was out. Effects didn't last too long, but it did work to stiffen up the shifts for a while.

So, using that principle, and what I think you're saying above, all that would be needed is the same size spring, but with a bit more compression strength...did I get it, or did I miss the boat yet again?
Hi Lee &Tom,
Not a lot of time today. Where are two ways to look at it. Increase the spring pressure, or reduce the pressure. If the spring pressure is increased the pressure applied to the band servo will be higher, but the time to full band pressure will be longer. Reducing the spring pressure, has the pressure to the servo delayed but hitting harder. Its the time that the slippage goes on for, that will destroy the facing.

The other thing that will affect this, is the type of trans that is used. Alough I have allways recommended the use of lower final drive ratios, for performance, I have not liked the use of a 4 cylinder trans. Sure it will fit, but it is not the same. They were not designed to handle the level of torque that the SVX delivers. Besides the extra clutch plate in the high clutch and transfer clutch, there will be other changes to the valve body and the applied pressures. The pressure and timing of the band will suit the lower torque, of the 4 cylinder. Pressure cost horsepower, so there is no point in them using a pressure in excess of what is needed to do the job.

I reckon that if you want a strong box for performance, you need to start with a SVX unit, preferable a Euro VTD unit, fitted with lower ratios.

Harvey.
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  #20  
Old 03-31-2005, 06:11 PM
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well it looks like my trannt is finaly going. i have to manualy shift it out of first or it will stay in it till redline. the shifts are real hard to. if anyone can point me in the direction of a good 4.44 and rear that will last i would love it. untill then my svx is faux manual.
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  #21  
Old 03-31-2005, 08:43 PM
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  #22  
Old 03-31-2005, 10:58 PM
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Quote:
Originally Posted by oab_au
What needs to be done is to send the valve body away to one of the good auto box builders (DRG, Level 10) . Get them to alter the spring or orifices, to allow the pressure to rise quicker, so the band is applied with less time to slip. I reckon you would only have to explain the problem, for them to know what to do. This modification will make the changes harder,and the box will not be as smooth, but it will make it survive the treatment longer.

Harvey.
Presumably, pulling the line pressure resistor will produce this effect? Or the L10 shift kit?
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  #23  
Old 04-01-2005, 07:19 AM
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Quote:
Originally Posted by soobiesvx93
geez what a way to get ur 1000th post eh? .....search car-part.com
If that was the case then every post would be his 1000th post
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  #24  
Old 04-01-2005, 11:21 AM
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well im gona have a transmission place install it. it will cost more but i can get a warrenty, and it this point thats what i need. what is invoulved with this swap. i know you have to swap the ls carrier from the svx diff to the 4.44 diff, but how is that done, and can a tranny shop do it?
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