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oneringer 01-17-2011 03:16 PM

Transmission care
 
Ok, we've got a '92 with 190K on it, and would like to make sure it keeps running. Can you folks tell me the best way to make the tranny last? Should we replace the fluid, or leave it alone? Any other tips? Thanks.

oab_au 01-17-2011 04:08 PM

Re: Transmission care
 
Quote:

Originally Posted by oneringer (Post 666966)
Ok, we've got a '92 with 190K on it, and would like to make sure it keeps running. Can you folks tell me the best way to make the tranny last? Should we replace the fluid, or leave it alone? Any other tips? Thanks.

If that is the original gearbox, and the ATF is still clean, you have done well.:) Just drain and top up the box every 20k, and drive it in 3rd around town.

If the oil is dark and smells burnt, look for another box. :(

Harvey.

longassname 01-19-2011 08:16 AM

Re: Transmission care
 
Replace the fluid but don't bother dropping the pan and changing the filter. It isn't really a filter; it's a wire screen and it doesn't get clogged. It's a waste of a pan gasket and screen. I like to use genuine Subaru transmission/power steering fluid. It's a quality fluid with good additives (subaru coolant is real good too but that's neigher here nor there). Add to it one bottle of lubegard atf protectant. This will make the fluid work better and last longer. Both the red bottle and the platinum which is a silver bottle are good--other brands and products are not equivalent. http://lubegard.com/~/C-113/LUBEGARD...ATF+Protectant
Upgrade/update your TCU with firmware with higher line pressure in 3rd and 4th gear to prevent high clutch and brake band slipping and eventual failure which otherwise plague SVXs.


Quote:

Originally Posted by oneringer (Post 666966)
Ok, we've got a '92 with 190K on it, and would like to make sure it keeps running. Can you folks tell me the best way to make the tranny last? Should we replace the fluid, or leave it alone? Any other tips? Thanks.


Huskymaniac 01-19-2011 08:21 AM

Re: Transmission care
 
Quote:

Originally Posted by longassname (Post 667126)
Replace the fluid but don't bother dropping the pan and changing the filter. It isn't really a filter; it's a wire screen and it doesn't get clogged. It's a waste of a pan gasket and screen. I like to use genuine Subaru transmission/power steering fluid. It's a quality fluid with good additives (subaru coolant is real good too but that's neigher here nor there). Add to it one bottle of lubegard atf protectant. This will make the fluid work better and last longer. Both the red bottle and the platinum which is a silver bottle are good--other brands and products are not equivalent. http://lubegard.com/~/C-113/LUBEGARD...ATF+Protectant
Upgrade/update your TCU with firmware with higher line pressure in 3rd and 4th gear to prevent high clutch and brake band slipping and eventual failure which otherwise plague SVXs.

So, really, the internal filter only acts as a filter when the tranny is already failing and throwing off parts big enough to get caught in the screen. Is that correct?

longassname 01-19-2011 08:47 AM

Re: Transmission care
 
that is correct.

Quote:

Originally Posted by Huskymaniac (Post 667129)
So, really, the internal filter only acts as a filter when the tranny is already failing and throwing off parts big enough to get caught in the screen. Is that correct?


Huskymaniac 01-19-2011 10:19 AM

Re: Transmission care
 
Quote:

Originally Posted by longassname (Post 667132)
that is correct.

Oh well, I guess that filter kit was a waste of money then. At least it wasn't too expensive.....

SoobCrazy 01-19-2011 11:10 AM

Re: Transmission care
 
You guys can pamper your autos all you like, I can't wait for mine to let go, but sadly, it seems to have been well taken care of.

STI 6 speed FTW!!!:lol:

oab_au 01-19-2011 05:14 PM

Re: Transmission care
 
Quote:

Originally Posted by longassname;667126[B
]Replace the fluid but don't bother dropping the pan and changing the filter. It isn't really a filter; it's a wire screen and it doesn't get clogged. It's a waste of a pan gasket and screen.[/B] ,,,,,,,,,,,,,,,,,,,,,,,,,,,.

Don't agree with this bit on the trans screen. There have been a few that I have heard of that have had the trans fail due to the blocked screen.
http://www.subaru-svx.net/forum/show...+filter+screen
There are probably others that replaced the box due to this happening.


Quote:

Originally Posted by longassname (Post 667126)
Upgrade/update your TCU with firmware with higher line pressure in 3rd and 4th gear to prevent high clutch and brake band slipping and eventual failure which otherwise plague SVXs

The slipping that destroys the band and high clutch, is a combination of high torque and low pressure. The low pressure is really due to the low rpm that the transmission pump runs at, when driving in 4th at low road speeds.
This combined with the high torque that the band and high clutch have to transmit, causes the slipping.

The line pressure can be increased, to add clutch pressure, by increasing the resistance of the dropping resistor. The resistance is 12 ohms increasing this to 25 ohms, by using two dropping resistors connected in series, will raise the pressure by about 30%. Increasing the pressure excessively will cause C and B solenoid binding, and hard changes.

The high torque is instantly reduced by 30% by shifting back to 3rd gear, this changes the overall ratio from 2.4:1 to 3.5 :1, the ATF output is increased by the same amount, and the heat produced by the torque converter is also reduced. It is the excessively high US ratio that has caused so much trouble. This is why fitting on trans that has a lower final drive ratio, like a Legacy 4.11:1 or an Outback 4.44:1, reduces the load on the box by about 17%/26%, results in a longer lasting, better preforming SVX.:)

Harvey.

longassname 01-19-2011 05:41 PM

Re: Transmission care
 
Na, there's no way a screen can get clogged. Aside from it being a very large surface area of a not very fine mesh I've never seen a clogged screen and I've rebuilt a lot of blown 4EAT transmisisons. I've had maybe half a dozen full of chunks of frictions that have fallen apart and maybe 4 full of chunks of bearings but I have never seen a clogged one. Even most blown 4EATs have clean screens.

The pump actually pumps a very large volume of fluid even at low RPMs. It incorporates a hydraulic feedback mechanism controling the volume of the vane pump so that the volume per rotation is higher at low rpms and lower at high rpms so that the actual volume pumped is equalized across the RPM spectrum. The sole reason for low line pressure at light cruise is the programming of the TCU. The stock programming has a very high solenoid a duty ratio under light cruise which bleeds of a whole lot of line pressure; there is no lack of fluid flow volume preventing a higher line pressure. That is easily accomplished by adjusting the main line pressure maps for each gear. Reprogramming the TCU with more line pressure in light cruise in 3rd and 4th gear or any gear's main map for that matter doesn't cause hard shifts or transfer clutch binding either. There are seperate maps and routines dictating the line pressure during gear changes and turns.

oab_au 01-19-2011 06:58 PM

Re: Transmission care
 
[QUOTE[QUOTE]]
Quote:

Originally Posted by longassname (Post 667176)
Na, there's no way a screen can get clogged. Aside from it being a very large surface area of a not very fine mesh I've never seen a clogged screen and I've rebuilt a lot of blown 4EAT transmissions. I've had maybe half a dozen full of chunks of frictions that have fallen apart and maybe 4 full of chunks of bearings but I have never seen a clogged one. Even most blown 4EATs have clean screens.[/QUOTE

Well I would like to help you , have a look here.
http://www.subaru-svx.net/forum/showthread.php?t=53883
This was the cause of the problem.

Quote:

The pump actually pumps a very large volume of fluid even at low RPMs. It incorporates a hydraulic feedback mechanism controlling the volume of the vane pump so that the volume per rotation is higher at low rpms and lower at high rpms so that the actual volume pumped is equalized across the RPM spectrum. The sole reason for low line pressure at light cruise is the programming of the TCU.
Not quite right. The pressure regulator, regulates the line pressure by controlling the pumps output. The total pumps out-put is controlled by the pumps speed, minus the quantity lost through the operational leaks and drains.

Quote:

The stock programming has a very high solenoid a duty ratio under light cruise which bleeds of a whole lot of line pressure; there is no lack of fluid flow volume preventing a higher line pressure. That is easily accomplished by adjusting the main line pressure maps for each gear
Yes the TCU does reduce the pressure at low throttle positions.
It can be accomplished a lot cheaper, by reducing the dropping resistor's resistance.:)

Quote:

Reprogramming the TCU with more line pressure in light cruise in 3rd and 4th gear or any gear's main map for that matter doesn't cause hard shifts or transfer clutch binding either. There are separate maps and routines dictating the line pressure during gear changes and turns
So when you are driving in 4th at a low road speed, with the line pressure increased from 50psi to 150psi and do a tight turn, you say this line pressure is reduced, so that the percentage of line pressure sent to the C solenoid is the same, as it should be. Don't think so.

As I have said, the main problem with the std SVX trans is the excessively high final drive ratio.

Harvey.

longassname 01-19-2011 07:22 PM

Re: Transmission care
 
Ugh, kind of a pain dealing with these line by line quotes....so I won't use them

so anyway....You're saying that someone had a loss of line pressure....changed his screen...and got his line pressure again? I find this hard to believe. If that is the case please say so directly. A picture where someone says he thought his filter was dirty doesn't do much for me.

no, the pump's output is controlled by a cam which changes the volume of the vane pump per rotation. The regulation of line pressure performed in the valve body you are describing is beside the point. The one and only point of any consequence is there is plenty of pump output to have much higher line pressure at light cruise and the only reason it isn't higher is because the tcu is bleeding it off.

If you really want to argue that tampering with the electrical connections is a better method of controling line pressure than setting the data right in the TCU firmware I'll just have to aggree to dissagree with you right now and not waste any more time.

Huskymaniac 01-19-2011 08:48 PM

Re: Transmission care
 
Oh no, another tranny debate. I am a pretty damn good engineer and these threads make my head spin. Of course, I am not an automotive engineer but an electrical/optical engineer so trannies are not my specialty.

I'm surprised no one mentioned bypassing the radiator with a higher flow oil cooler. I bought, but have not yet installed, a 10,000 GVW flex-a-lite cooler which has a pretty small footprint and a low flow resistance.

I agree with Mike on Lubegard. I have had great luck with the stuff and the folks at BITOG rave about it. It is an ester based additive which should help reduce operating temperatures. It is like water wetter for your tranny. Although I like Lubegard, I personally opted for Redline with no additives over Subaru ATF with Lubegard but I think that is a great option too.

From what I have gleened from the many threads on the subject, increasing the dropping resistor would help the line pressure a little but Mike's TCU map changes would help it a lot at those critical low RPM, low throttle conditions.

If stupid little crap like valve cover gaskets and O2 sensors ever stop going, I may be able to get the wife to agree to letting me buy Mike's TCU upgrade or valve bodies or both. Maybe a group buy by 1996 owners for the TCU upgrade would help spread out the cost of Mike mapping stuff out for our newer TCUs. (hint...hint to 1996 owners)

rlutz 01-20-2011 08:23 AM

Re: Transmission care
 
Quote:

Originally Posted by longassname (Post 667176)
Na, there's no way a screen can get clogged. Aside from it being a very large surface area of a not very fine mesh I've never seen a clogged screen and I've rebuilt a lot of blown 4EAT transmisisons. I've had maybe half a dozen full of chunks of frictions that have fallen apart and maybe 4 full of chunks of bearings but I have never seen a clogged one. Even most blown 4EATs have clean screens.

The pump actually pumps a very large volume of fluid even at low RPMs. It incorporates a hydraulic feedback mechanism controling the volume of the vane pump so that the volume per rotation is higher at low rpms and lower at high rpms so that the actual volume pumped is equalized across the RPM spectrum. The sole reason for low line pressure at light cruise is the programming of the TCU. The stock programming has a very high solenoid a duty ratio under light cruise which bleeds of a whole lot of line pressure; there is no lack of fluid flow volume preventing a higher line pressure. That is easily accomplished by adjusting the main line pressure maps for each gear. Reprogramming the TCU with more line pressure in light cruise in 3rd and 4th gear or any gear's main map for that matter doesn't cause hard shifts or transfer clutch binding either. There are seperate maps and routines dictating the line pressure during gear changes and turns.


Michael, why did Subaru program the original TCU for such light line pressure in light cruise?

longassname 01-20-2011 09:32 AM

Re: Transmission care
 
Subaru used the same solenoid a map for all 4 gears. They probably used the same solenoid a map in all their other model cars and for every year since they first released the 4eat. It was probably generated by a perfectly reasonable formula that calculated the minimal line pressure necessary to hold the rated carrying capacity of the transmission. It obviously works fine in 1st and 2nd gear which use larger clutch packs and it obviously works fine in other model cars which aren't as heavy as the SVX and have a higher gear ratio than the SVX.

The reason solenoid A and the maps and routines controling it are included in the system to begin with is to minimize the pressure the pump has to pump against. Pumping against pressure requires power so minimizing the pressure increases efficiency. Increasing line pressure 15% during light cruise might be enough to stop slipping if all the seals in the transmission and the high clutch are still very good. Maybe a 40% increase would do it. It's not practical start low and see where transmissions stop burning up. Putting it close to max pressure in the main map is an easy way to definitively fix the problem and the amount of power it takes to spin the pump against the higher pressure really isn't significant--especially compared to the power loss from erroring on the other side where the high clutch still slips.

SoobCrazy 01-20-2011 10:53 AM

Re: Transmission care
 
Quote:

Originally Posted by Huskymaniac (Post 667191)
Maybe a group buy by 1996 owners for the TCU upgrade would help spread out the cost of Mike mapping stuff out for our newer TCUs. (hint...hint to 1996 owners)

I would much prefer an flashable OEM ECU to a TCU upgrade on my 1996. Let the autos die!


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